@prefix vivo: . @prefix edm: . @prefix ns0: . @prefix dcterms: . @prefix skos: . vivo:departmentOrSchool "Applied Science, Faculty of"@en, "Civil Engineering, Department of"@en ; edm:dataProvider "DSpace"@en ; ns0:degreeCampus "UBCV"@en ; dcterms:creator "Man, Christopher Zhun Ting"@en ; dcterms:issued "2012-10-19T23:09:23Z"@en, "2012"@en ; vivo:relatedDegree "Master of Applied Science - MASc"@en ; ns0:degreeGrantor "University of British Columbia"@en ; dcterms:description """The railcar cover solution is aimed at providing an aerodynamic solution for the transport of coal. The system includes the use of a handling system that is currently under development by a third party. This study seeks to aid in the implementation of a performance based design approach to the railcar cover system. The performance based design approach is a method that utilizes modern analysis tools to provide designs that are more robust than typical prescriptive design procedures (such as the pure use of limit states in codes). A general procedure in establishing performance guidelines is provided in this study, as well as a procedure on conducting a performance based design. Also described in this study is a comparison of design configurations proposed for the cover system. Through the use of CFdesign fluid dynamics analysis software, various engineering demand parameters are measured for each railcar cover configuration including railcar flow rates and cover pressure distributions. This data are presented purely as a comparison, due to the high variability and lack of confidence inspired by validation studies. Validation studies were also presented to compare the various parameters and analysis options available with the CFdesign software, which may be used to further understand the correct implementation methods of CFdesign software for practical use."""@en ; edm:aggregatedCHO "https://circle.library.ubc.ca/rest/handle/2429/43514?expand=metadata"@en ; skos:note "Developing Performance Based Design Guidelines for the Railcar Cover System by Christopher Zhun Ting Man B.A.Sc., The University of British Columbia, 2012 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in THE FACULTY OF GRADUATE STUDIES (Civil Engineering) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) October 2012 © Christopher Zhun Ting Man, 2012 ii Abstract The railcar cover solution is aimed at providing an aerodynamic solution for the transport of coal. The system includes the use of a handling system at is currently under development by a third party. This study seeks to aid in the implementation of a performance based design approach to the railcar cover system. The performance based design approach is a method that utilizes modern analysis tools to provide designs that are more robust than typical prescriptive design procedures (such as the pure use of limit states in codes). A general procedure in establishing performance guidelines is provided in this study, as well as a procedure on conducting a performance based design. Also described in this study is a comparison of design configurations proposed for the cover system. Through the use of CFdesign fluid dynamics analysis software, various engineering demand parameters are measured for each railcar cover configuration including railcar flow rates and cover pressure distributions. This data are presented purely as a comparison, due to the high variability and lack of confidence inspired by validation studies. Validation studies were also presented to compare the various parameters and analysis options available with the CFdesign software, which may be used to further understand the correct implementation methods of CFdesign software for practical use. iii Table of Contents Abstract ........................................................................................................................ ii Table of Contents ....................................................................................................... iii List of Tables ............................................................................................................. vii List of Figures ........................................................................................................... viii List of Abbreviations ................................................................................................ xii Acknowledgements .................................................................................................. xiii Chapter 1: Introduction........................................................................................... 1 1.1 Coal Transportation ................................................................................................. 1 1.2 Goals ........................................................................................................................ 2 Chapter 2: Railcar Cover System ........................................................................... 3 2.1 Handling ................................................................................................................... 3 2.2 Structure ................................................................................................................... 4 2.3 Previous Work ......................................................................................................... 4 Chapter 3: Design Approaches ............................................................................... 6 3.1 Limit States Design .................................................................................................. 6 3.2 Performance Based Design ...................................................................................... 7 3.2.1 Risk Assessment .................................................................................................. 8 3.2.2 General Procedure ............................................................................................... 9 3.2.3 Notable Works ................................................................................................... 13 3.2.4 General Guidelines ............................................................................................ 15 3.2.5 Guidelines for the Railcar Cover System .......................................................... 19 iv Chapter 4: Computational Fluid Dynamics......................................................... 22 4.1 Fluid Dynamics ...................................................................................................... 22 4.1.1 Bernoulli’s Principle .......................................................................................... 22 4.1.2 Navier Stokes ..................................................................................................... 23 4.2 CFD ........................................................................................................................ 24 4.2.1 Stages of CFD Analysis ..................................................................................... 26 4.2.2 Model Preparation ............................................................................................. 27 4.2.2.1 Autodesk Inventor ....................................................................................... 27 4.2.2.2 CFdesign Software ...................................................................................... 29 4.2.2.2.1 Solution to Angle of Attack problem ................................................... 29 4.2.2.2.2 Boundary Conditions ........................................................................... 31 4.2.2.2.3 Materials .............................................................................................. 32 4.2.2.2.4 Mesh Size ............................................................................................. 34 4.2.2.2.5 Solving ................................................................................................. 36 4.2.2.2.6 Results .................................................................................................. 37 Chapter 5: CFdesign Models ................................................................................. 38 5.1.1 Single Railcar Models ....................................................................................... 38 5.1.2 Double Railcar Models ...................................................................................... 39 5.2 Flow Rates ............................................................................................................. 41 5.2.1 Single Railcar Models ....................................................................................... 44 5.2.2 Double Railcar Models ...................................................................................... 50 5.3 Pressures ................................................................................................................ 54 5.4 Validation Models .................................................................................................. 61 5.4.1 Inlet and Outlet Parameters ............................................................................... 61 v 5.4.2 Mesh Sizes ......................................................................................................... 72 5.4.2.1 Layer Adaptation ......................................................................................... 76 5.4.2.2 Iteration Count ............................................................................................. 77 5.4.2.3 Convergence ................................................................................................ 78 Chapter 6: Conclusion ........................................................................................... 81 6.1 Performance Based Design .................................................................................... 81 6.2 Computational Fluid Dynamics Analysis .............................................................. 81 6.2.1 Single Railcar Model ......................................................................................... 82 6.2.2 Double Railcar Model ....................................................................................... 82 6.2.3 Validation Study ................................................................................................ 83 Appendices ................................................................................................................. 86 Appendix A Railcar Cover Drawings ................................................................................. 86 Appendix B Railcar Drawings ............................................................................................ 88 Appendix C Results from CFdesign ................................................................................... 89 C.1 Data for Model 2RcCG0.625 G28in .................................................................. 89 C.2 Data for Model 2RcCG0.625 G28in S24in ....................................................... 92 C.3 Data for Model 2RcCG1 G28in ......................................................................... 94 C.4 Data for Model 2RccG1 G28in S24in ............................................................... 96 C.5 Data for Model 2RcCG1 G40in ......................................................................... 98 C.6 Data for Model Rc ........................................................................................... 100 C.7 Data for Model RcCG0.5 ................................................................................. 102 C.8 Data for Model RcCG0.625 ............................................................................. 103 C.9 Data for Model RcCG0.625 ............................................................................. 104 C.10 Peak Cover Pressures ....................................................................................... 105 vi C.11 Cover Pressure Comparisons for Double Railcar Models ............................... 106 C.12 Flow Rate Comparisons for Double Railcar Models ....................................... 107 vii List of Tables Table 3.1 Performance Criteria Based on Impact Action for Rockfall Structures ................. 17 Table 3.2 Performance Guidelines for Railcar Cover System ................................................ 21 Table 5.1 Graphing Points used for Velocity and Pressure Measurements ............................ 44 Table 5.2 Comparison of Flow Rates for Single Railcar Models ........................................... 48 Table 5.3 Comparison between Railcar to Cover Gaps at 1m/s Wind speed ......................... 50 Table 5.4 Flow Rate Comparison for Double Railcar Configurations ................................... 52 Table 5.5 Flow Rate Comparison for Installation of Shutter in 0.625 inch Railcar to Cover Gap Model .............................................................................................................................. 53 Table 5.6 Flow Rate Comparison for Installation of Shutter in 1 inch Railcar to Cover Gap Model ...................................................................................................................................... 53 Table 5.7 Flow Rate Comparison for Increase from 28 inch to 40 inch Cart-to-Cart Gap Model ...................................................................................................................................... 54 Table 5.8 Pressure Comparison for Installation of Shutter in 0.625 inch Railcar to Cover Gap Model ...................................................................................................................................... 58 Table 5.9 Pressure Comparison for Installation of Shutter in 1 inch Railcar to Cover Gap Model ...................................................................................................................................... 58 Table 5.10 Pressure Comparison for Increase from 28 inch to 40 inch Cart-to-Cart Gap Model ...................................................................................................................................... 59 Table 5.11 Inlet Outlet Validation Model Parameters ............................................................ 63 viii List of Figures Figure 3.1 Performance Based Wind Design Flow Chart ....................................................... 12 Figure 4.2 Flow Line Visualization for Railcar and railcar cover with 90 degree angle of attack ....................................................................................................................................... 27 Figure 4.3 Railcar Cover Model used for Analysis ................................................................ 28 Figure 4.4 Boundary Conditions for Railcar and Railcar Cover Model ................................. 32 Figure 4.5 CFdesign Material Distinctions ............................................................................. 33 Figure 4.6 Mesh Shapes for 3D and 2D Objects in CFdesign ................................................ 34 Figure 4.7 Railcar and Railcar Cover System Fully Meshed.................................................. 36 Figure 5.1 Shutter Attached to End of Railcar (Elevation View) ........................................... 39 Figure 5.2 Shutter Attached to End of Railcar (Plan View) ................................................... 40 Figure 5.3 Angles of Attack .................................................................................................... 41 Figure 5.4 Railcar Orientation Labels ..................................................................................... 42 Figure 5.5 Graphing Lines for Velocity and Pressure Measurements .................................... 42 Figure 5.6 Graphing Lines for Velocity and Pressure Measurements (Elevation View 1) .... 43 Figure 5.7 Graphing Lines for Velocity and Pressure Measurements (Elevation View 2) .... 43 Figure 5.8 Mesh of Graphing Lines for Velocity and Pressure Measurements for Open Railcar ..................................................................................................................................... 45 Figure 5.9 Flow Rate Comparison between Single Railcar Models at 1m/s Wind speed ...... 46 Figure 5.10 Flow Rate Comparison between Single Railcar Models at 10m/s Wind speed .. 47 Figure 5.11 Flow Rate Comparison between Single Railcar Models at 100km/h Wind speed ................................................................................................................................................. 47 ix Figure 5.12 Flow Rate Comparison for Railcar to Cover Gap Distances at 1m/s Wind speed ................................................................................................................................................. 48 Figure 5.13 Flow Rate Comparison for Railcar to Cover Gap Distances at 10m/s Wind speed ................................................................................................................................................. 49 Figure 5.14 Flow Rate Comparison for Railcar to Cover Gap Distances at 100km/h Wind speed ....................................................................................................................................... 49 Figure 5.15 Flow Rate Comparison for Double Railcar Configurations at 1m/s Wind speed 51 Figure 5.16 Flow Rate Comparison for Double Railcar Configurations at 10m/s Wind speed ................................................................................................................................................. 51 Figure 5.17 Flow Rate Comparison for Double Railcar Configurations at 100km/h Wind speed ....................................................................................................................................... 52 Figure 5.18 Cover Segments for Pressure Designation .......................................................... 55 Figure 5.19 Cover Pressure Comparisons for Double Railcar Configurations at 1m/s Wind speed ....................................................................................................................................... 56 Figure 5.20 Cover Pressure Comparisons for Double Railcar Configurations at 10m/s Wind speed ....................................................................................................................................... 56 Figure 5.21 Cover Pressure Comparisons for Double Railcar Configurations at 100km/h Wind speed.............................................................................................................................. 57 Figure 5.22 Inlet Outlet Validation Model ............................................................................. 62 Figure 5.23 Colour Code for CFdesign Boundary Conditions ............................................... 63 Figure 5.24 Inlet Outlet Validation Boundary Conditions - Model A .................................... 63 Figure 5.25 Inlet Outlet Validation Boundary Conditions - Model B .................................... 64 Figure 5.26 Inlet Outlet Validation Boundary Conditions - Model C .................................... 64 x Figure 5.27 Inlet Outlet Validation Boundary Conditions - Model D .................................... 64 Figure 5.28 Inlet Outlet Validation Boundary Conditions - Model E .................................... 65 Figure 5.29 Inlet Outlet Validation Boundary Conditions - Model F ..................................... 65 Figure 5.30 Inlet Outlet Validation Boundary Conditions - Model G .................................... 65 Figure 5.31 Inlet Outlet Validation Boundary Conditions - Model H .................................... 66 Figure 5.32 Inlet Outlet Validation Boundary Conditions - Model I ..................................... 66 Figure 5.33 Inlet Outlet Validation Study - Graphing Line used for Velocity Measurements67 Figure 5.34 Inlet Outlet Validation Study Velocity Graph - Single Inlet ............................... 67 Figure 5.35 Inlet Outlet Validation Study Velocity Graph - Double Inlet ............................. 68 Figure 5.36 Inlet Outlet Validation Study Velocity Graph - Triple Inlet ............................... 68 Figure 5.37 Inlet Outlet Validation Study - Measurement Point ............................................ 69 Figure 5.38 Inlet Outlet Validation Study - Point Velocity Comparison ............................... 70 Figure 5.39 Inlet Outlet Validation Study - Point Velocity Comparison (Without Model C) 70 Figure 5.40 Inlet Outlet Validation Model - Flow Visualization for Triple Inlet Model ....... 71 Figure 5.41 Mesh Size Validation - Velocity Measurements (All) ........................................ 73 Figure 5.42 Mesh Size Validation - Velocity Measurements (Only Layer Factor 0.1) .......... 73 Figure 5.43 Mesh Size Validation - Velocity Measurements (Only Single Layers) .............. 74 Figure 5.44 Mesh Size Validation - Pressure Measurements (All) ........................................ 74 Figure 5.45 Mesh Size Validation - Pressure Measurements (Only Layer Factor 0.1) .......... 75 Figure 5.46 Mesh Size Validation - Pressure Measurements (Only Single Layer) ................ 75 Figure 5.47 Mesh Size Validation - Velocity Measurements (Layer Adaptation) ................. 76 Figure 5.48 Mesh Size Validation - Pressure Measurements (Layer Adaptation) ................. 76 Figure 5.49 Mesh Size Validation - Velocity Measurements (Iteration Count) ..................... 77 xi Figure 5.50 Mesh Size Validation - Pressure Measurements (Iteration Count) ..................... 77 Figure 5.51 Mesh Size Validation – Convergence (Velocity) ................................................ 79 Figure 5.52 Mesh Size Validation – Convergence (Pressure) ................................................ 80 xii List of Abbreviations CFD – Computational Fluid Dynamics DM – Damage Measures DV – Decision Variables EDP – Engineering Demand Parameters xiii Acknowledgements I would like to thank my supervisor Dr. Siegfried Stiemer for his aid and wonderful guidance. Without his help, this project would not be possible and I am thankful for the opportunities he has given me. I would also like to thank the employees of Dynamic Structures Ltd for their aid during the process of this study. I owe great thanks to Ye Zhou, Nathan Loewen, and David Halliday for their guidance and for providing an excellent environment for me to focus on my thesis. I would like to thank Dr. Wudi for his prompt help when his assistance was requested. I would also like to thank my friends for their continual support and limitless abilities in making me laugh. Especially Ryan Wang who has made my Masters program a new adventure every day. I would like to thank my parents and my brother for lending me an ear when I needed it. I would most of all like to thank my supportive girlfriend Helen for her tutorship. xiv Dedication To my parents for letting me fly high at times and grounding me at others. 1 Chapter 1: Introduction This thesis will focus providing a brief overview of utilizing a performance based design approach to analyze the effectiveness in design of the railcar cover system as well as provide a comparison of various railcar cover design configurations through the use of computational fluid dynamics (CFD) software. 1.1 Coal Transportation Coal is an organic material that is most often found in subsurface deposits. Its formation is mostly attributed to high pressure and temperature environments that aid in altering its chemical structure to its state as a carbon rich combustible material. It is most commonly used for the generation of energy around the world and also can be used to aid in the production of steel and iron. In 2010, the Canadian coal industry confirmed an approximate 8.7 billion tonnes of coal in deposits. This number has been extrapolated to nearly 190 billion tonnes of coal estimated to reside within Canada. In 2007, it was recorded that Canada exported nearly 31 tonnes of coal, or $2.9 billion. This significant market interest in the production and transportation of coal is what brought interest to this project. Coal dust has become a major concern that many coal transporters have sought to mitigate. Coal dust losses pose a serious hazard to the environment and present significant economic losses to the industry. Contamination of the railway track ballast can lead to 2 structural damage of the railway track, causing concern in terms of safety as well as becoming a maintenance burden. In order to address this phenomenon, the designer has proposed a cover solution to aid in loss of coal dusts during transport, as well as provides an aerodynamic solution to the open railcar. 1.2 Goals It is the goal of this study to provide a more comprehensive analysis of the railcar cover. This study will seek to utilize CFD software to better understand the efficiencies and design configurations of the railcar cover system, as well as provide recommendations and procedures regarding the establishment of a performance based design guidelines for the railcar cover system. 3 Chapter 2: Railcar Cover System The railcar cover system was specifically designed for coal transport. The goal of the cover system was to limit the amount of air drag and improve the fuel economy of empty railcars while also minimizing the amount of coal dust-loss due to wind vortices. The cover system features a unique flexible hatch with attachments that adheres to the edges of the railcar at key structural locations. The flexible nature of the cover system allows for ease of handling without contributing a significant increase in mass to the railcar. The benefits presented by the cover system are focused on a few key concepts: limiting coal dust and product loss, reducing overall railcar drag, and allowing for a handling system that can load and unload at an efficient rate. This study will primarily focus on the limitation of dust and product losses. 2.1 Handling The handling mechanism was designed by a third party and features a mobile handling arm that is capable of reliably removing and reattaching the cover system while the locomotive is in motion. The handling system was designed to operate in an enclosed environment such that sudden gusts and environmental conditions would not impact the operation of the handling machine and to avoid damaging the cover system during the handling process. The handling process of the cover system was designed to allow the locomotive to continue travelling at a speed of 1.6mph (0.715m/s). Thusly, a wind attack speed of 1m/s was 4 included in the analysis to explore the effects of wind speed on the cover system as well as the fluid exchange between the railcar contents and the environment. 2.2 Structure The cover system is composed of a thin glass-reinforced plastic shell supported by longitudinal ribs running perpendicular to the length of the railcar. These structural ribs provide the primary structural component while the rigidity of the glass-reinforced plastic shell distributes wind pressures on the cover system into the structural ribs. The entire system is attached to the railcar at 12 locations with steel latches that suspends the cover system over the railcar. A 5/8 inch gap has been proposed between the cover and the railcar. The 5/8 inch gap exists to improve the design and handling of the cover system. Concerns were that high wind and travel speeds created a suction pressure around the railcar and the cover system. Upon reaching lower speeds, residual negative pressures would remain within the railcar, leading to unpredictable suction forces that would negatively impact the railcar, its contents, and the handling system. Addressing this issue was the concept of providing an open air gap between the cover and the railcar to aid in equalizing the negative pressure within the railcar. 2.3 Previous Work A previous study conducted by Johann Fridriksson in 2011 included the finite element analysis of the cover system under static pressure loadings. These pressure loadings were established from a CFD analysis completed by STX Europe in 2009. The report focused on applying three load cases onto a model that featured two and a half successive railcars 5 with the half cart at the front. The load cases featured included angles of attack of: 0 degrees (parallel to the direction of travel), 90 degrees (perpendicular to the direction of travel), and 29 degrees. Wind speeds for these cases were 63m/s, 33m/s, and 58m/s respectively. For each case, average pressure on the railcar cover system was measured; the maximum pressures were utilized for the subsequent finite element analysis. Fridriksson used ANSYS, a finite element analysis tool, to evaluate the response of the cover system under the pressures proposed by STX Europe. This analysis determined several key structural parameters such as the natural period of the structure. The natural system period was used to determine whether periodic shedding vortices were capable of causing system resonance and structural damage. Along with this dynamic analysis of the structural system, Fridriksson also conducted a static analysis of the cover system under a uniform pressure of 2140 Pa suction. Fridriksson also conducted a post damage analysis that highlighted issues surrounding the cover design. Perpendicular cuts were introduced to the cover shell to determine structural performance under a damaged state. It was found that displacements for the cover system under this damaged state were in the order of 1.6 metres, clearly excessive for the system. This indicates that an evaluation of the loads applied to the cover system should be more carefully analyzed, and that perhaps a different design approach would be appropriate. 6 Chapter 3: Design Approaches The focus of this study is to acknowledge and bridge the gap between design goals and performance expectations by providing realistic fluid flow data and comprehensive flow analysis, this study aims to provide insight on the expected performance for a target design. Performance based designs provide an excellent bridge between the current strength based designs. By mitigating risk and bridging the information gap between product expectations and design specifications, performance based designs allow for a structure to be analyzed at several stages to ensure that a robust design encompassing all stakeholder concerns are met. The key to providing this type of design is establishing a practical link between occupant demands and structural performance. This also requires a working guideline that governs the expected demands and allows for these demands to be translated into an engineering design. 3.1 Limit States Design Current engineering designs utilize a prescriptive design approach. Limit states are determined appropriately to ensure a structure performs as designated through the establishment of various structure response and strength requirements. The two most common limit states are: ultimate limit states and allowable limit states. Ultimate limit states focus on the collapse load for the structure. Relevant factors are applied accordingly to both loads and material resistances, and the structure is designed to 7 survive these designated collapse loads. Typical ultimate limit states will ensure: design of system redundancies, avoiding loss in equilibrium, and avoidance of unacceptable yielding, rupture, or fracture in structural components. Allowable limit states are established to ensure that the structure performs appropriately according to its required uses. This design tier considers common loading and seeks to eliminate structural response that would react adversely to these common loads. Typical allowable limit states seek to address: structural vibration (for machinery operation and occupant comfort), fatigue stresses, as well as structural deflections that would damage non-structural components. Both these design methods are often utilized in a prescriptive manner. Designers seek to create designs that satisfy standardized codes. This design approach has been proven to be cost effective and economically efficient. However, when irregular projects arise, standardized codes can often place limits on a project by disallowing certain avenues and options of design. As a result, designers have brought about performance based design techniques to freely express themselves while providing safe and efficient designs. 3.2 Performance Based Design Kalay identifies the shortfalls of engineering and architectural design processes which have primarily been focused on a process-based procurement method. This method finely divides the procurement method into stages where design, construction and management are key components of the life cycle of a structure. The final goal the design process is keyed to 8 be solving the puzzle between finding a solution that fits both form and function. Kalay proposes a method in which both form and function can be achieved utilizing modern design and analysis tools: performance evaluation. Performance based design evaluates the structure from concept to decommission. The evaluation is conducted through objective parameters that recognize and grade a designs performance in satisfying its function. The advantages of this design methodology are that it provides a project options and different paths in which a similar solution can be achieved for an identical problem. The introduction of context into this methodology highlights that each given set of decisions output a specific behaviour. Context allows a method in which each particular form and function can be evaluated given a set of decisions. These decisions decide whether or not a specific form and function responds favourably considering its expected behaviour. Together, form, function, and context allow the development of behaviours to be understood and evaluated through the use of modern tools. By filling the gap in knowledge of a projects capabilities in satisfying the end goal of a project, and providing adequate tools in which comparisons can be made, performance based design provides a better understanding of a projects concept and objectives, and can lead to an optimal decision to be made based on purely objective measurements. 3.2.1 Risk Assessment Risk assessment seeks to utilize knowledge tools to make engineering decisions. These knowledge tools utilize previous experiences and knowledge to build statistical models for each event and subsequent outcome for a project. By accommodating uncertainties, 9 project response and behaviour can better be assessed in terms of economic benefit and utility. Assessments are made typically by weighing various project configurations and decisions based on expected economic impact and cost values. The key to conducting these assessments are by establishing what performance expectations are of importance to stakeholders, these expectations are labeled as decision variables (DV). 3.2.2 General Procedure The basis of performance based design capitalizes on the use of risk assessment as a tool. Performance based design uses risk assessment in various steps of its design process to determine probabilistic outcomes of each facet of design from loadings to structural performance to economic outcomes. By fully understanding and accommodating the uncertainty that lies in every facet of design, the performance based design approach can utilize the limit states design method by customizing a design threshold for values specific to a designs condition and situation. The end product is a design that satisfies stakeholder requirements and translates user performance targets into engineering demand parameters (EDP). Ciampoli et al. stated that the importance of the performance based design lies in the designation of DVs and the linking of these stakeholder relevant DVs to design relevant parameters. These probabilistic variables describe specific structural performance thresholds that can be directly related to stakeholder criteria. For a structure designed for wind loading events, the first steps to creating performance targets would be to establish probabilistic 10 relationships between the expected performance tiers and the wind intensities (categorized by return periods). The structural risk is then assessed for each DV tier, and a probability of exceedance is calculated to demonstrate the probability that a DV threshold would be exceeded. The key to optimizing the project would then to make project decisions that seek to reduce total risk while maximizing utility (and thus reducing economic costs). A summary of the steps required for the performance based wind design of a structure are listed below: 1. Determine DVs relevant to stakeholders 2. Select site specific wind parameters 3. Determine structure response due to site specific parameters 4. Define DVs with respect to the structure response to qualify performance 5. Evaluate structural risk by reducing total risk independently into: site specific risk and structure specific risk 6. Utilize random number simulators to attain realistic interpretations of probabilistic data in terms of economic outcomes (ie. Monte Carlo simulation) 7. Decide on a final design given the probabilistically-expressed final product and economic outcomes of each design The general procedure to constructing performance based design guidelines consists of defining key requirements and relationships. DVs are quantitative values relevant to stakeholders. For a structure designed against seismic or wind storm events, typical DVs would be the number of lives lost during an event, economic losses as a result of an event, amount of time required to repair a structure, and occupant discomfort. These DVs become a bastion for design targets. 11 Designs then combine two systems: the environmental information with site specific loading information, and the structural system. Combining these two systems, a structural behaviour is measured. These measurements describe the structural behaviour and are labeled as EDP. In performance designs of structures for seismic loads, these EDP include: structural drift, accelerations, and structural member stresses. Threshold limits established to these EDP are labeled as damage measures (DM). DMs provide a relationship between DVs and EDP by establishing various tiers of descriptive performance for a certain level of structural response. Each set of parameters requires an analysis however. • Risk and loss analyses aids in the development of DVs. • Damage analyses aid in the establishing of damage measures by determining what levels of damage pertain to a perceived level of performance. • Structural analyses are required to determine EDP. • Site hazard analysis determines environmental information required to determine loading parameters. • Through the use of analysis tools, it is possible to attain each step required conduct a performance based design. Ciampoli et al. present a diagram that visually describes the steps required to performing a performance based wind design for a structure. 12 Figure 3.1 Performance Based Wind Design Flow Chart Source: Ciampoli et al., 2011 An example application of this design approach was also conducted by Ciampoli et al. in their research regarding the use of performance based wind design procedures. Researchers applied this design to a long span suspension bridge. The bridge structure was to serve as a roadway on the outer edges and also allow for railway traffic through the centre of the bridge deck. The performance guideline for the bridge structure was divided into two performance categories: high performance and low performance. High performance dictated serviceability limits for the bridge structure, including deck vibrations. Low performance pertained to collapse loads and ensured that structural safety would be preserved under flutter stability (structure resonance and collapse due to the constructive displacements produced by periodic wind loads interacting with the natural period of the system). 13 Three levels of performance were determined for the system: two for serviceability limit states and one for ultimate limit states. High performance limit states dictated that serviceability limits perform at two levels: “full serviceability” and “partial serviceability”. These high performance states contained DVs detailing the level of service allowed for the bridge structure. Full serviceability would able to continue servicing expected vehicle traffic where as partial serviceability would only allow railway traffic through. Low performance levels would ensure that the bridge structure maintain structural integrity through a wind storm type event. EDP for each of the performance levels were also established for the bridge structure. High performance levels were measured using EDP that described the rotational velocity as well as the acceleration of the deck in vertical and longitudinal direction. Low performance focused primarily on collapse prevention, and ensured that the structure be capable of surviving flutter instability caused by high periodic gust forces. The EDP for the ultimate limit state criteria dictated the measurement of the total structural and aerodynamic damping ratio. The DM threshold on damping was limited to a minimum of 0 to ensure that the system was capable of dissipating the energy introduced by wind loads. 3.2.3 Notable Works Yang et al. identifies the positive impact and effectiveness of the utilization of performance based design in the context of earthquake engineering. This design methodology was utilized to attempt to quantify six prequalified steel seismic force resisting systems. A 14 complete economic analysis was then conducted to determine the expected repair and maintenance costs incurred by a seismic event. Building elements were categorized into ‘performance groups’, allowing the assessment of expected damage and economic impact. Each performance group translated a different EDP (drift, acceleration or other) into an economic cost of repair and level of expected damage. For instance, interior non-structural components related damage and repair costs to interstory drift. Damage states were then established for each level of response such that expected damage extent and repair costs were able to be directly translated from an a EDP. These damage states relate directly to the performance guidelines that are utilized by performance based design methods. The damage states for each performance group were divided into performance levels: DS1 with no damage at all, DS2 with minor damage, and DS3 with severe damage. Performance groups would have also had DMs thresholds established for levels of performance. The development of product evaluation guidelines could then be utilized during the design process to provide an economic assessment of expected damage and repair costs for a particular lateral force resisting system when combined with probabilistic site specific loading information. Damage states allow for the quantifying and evaluation of a system based on its response. The system response can then be directly related to damage values due to previous statistical data documenting the susceptibility and probability of damage given a seismic 15 event. The statistical nature of damage and repair costs creates an issue with the uncertainty that lies with each event and load scenario. This uncertainty is mitigated by establishing decision trees that analyze costs by likelihood of occurrence and produce an expected cost value for the total project. 3.2.4 General Guidelines Guidelines are often produced through the identification of satisfactory levels of structure performance. By providing a base for structural performance, it is possible to relate the risk involved with each level of performance to a level of design given the analysis of expected loads and demands that the structure may face. The structure would then be designed to those levels of performance given the heighted levels of load, accurately assessing risk involved in the design. In structures designed for seismic events, these levels of performance are typically separated into post-event structural system descriptions such as: Immediate Occupancy, Life Safety, and Collapse Prevention. These levels are then assigned predetermined measurements of performance such as: inter-story drift, inelastic deformations, and peak roof velocities. A group of Japanese researchers from Hokukon Co, Kanazawa University, and Nihon Samicon Co produced a study composing performance criteria for reinforced concrete beams under impact loading. This study evaluated characteristics key to understanding the performance demands required from rockfall protection structures. The strength-based design method is generally considered inappropriate for the low impact dynamic loadings typically 16 observed by rockfall structures, and as such, a performance based design criteria was composed to focus on catering to the specific nature and demands of these structures. The researchers attained experimental data for a variety of beams and reinforcement arrangements and utilized test results to construct a performance criterion. Impact tests were conducted on various rockfall protection elements with a range of design strengths. From these experiments, researchers developed an empirical relationship between the impact force and time. Using these calculated values and experimental data for impact force and time, researchers applied working knowledge to develop performance guidelines. It was decided by stakeholders that the developed performance guidelines should specifically address the level loading by frequency, the damage state expected, a descriptive level of safety for occupants under the rockfall structures during a rockfall event, and the subsequent serviceability and repair required. The table below describes these expected characteristics. 17 Table 3.1 Performance Criteria Based on Impact Action for Rockfall Structures Impact Action Explanation by occurrence Damage Safety Serviceability Repair L evel 1 The action corresponding to the maximum energy with the occurrence expected to be once or twice during several decades or the design working period of the road No damage Safe to traffic vehicles and passing persons No obstacle No need Level 2 The action corresponding to the maximum energy with the occurrence expected to be within 100 years Damage is limited within an allowable range Safe to traffic vehicles and passing persons No obstacle Small-scale repair Level 3 The action corresponding to the largest energy with the possibility of occurrence by strong earthquake etc. There is no fatal damage Safe to passing persons Traffic restriction Repair or reinforcement Source: Tachibana et al., 2010 Each level of performance is tied to a loading event, a level of acceptable damage, as well as characteristic descriptions such as safety concerns, serviceability requirements, and level of repairs required. Loading events are separated into probabilities of occurrence, with specified return periods detailing the level of severity of loading. Damage limits are qualitatively prescribed to allowable ranges based on owner established expectations. Safety requirements are generally prescribed to practical limits as to limit loss of life in all cases. Serviceability and repair expectations are usually detailed through an extensive cost-risk analysis that analyzes the relationship between capital project investments and estimated repair costs. This study is an excellent example to the structuring of performance guidelines for cover systems. The design of the performance guidelines utilized several key steps including 18 the establishment of load cases, the analysis of system responses, and the statement of required system performance under various tiers of loading conditions. Another study conducted by researchers from Sapienza Universita di Roma in Italy utilized performance based design approach of to designing structures for high wind loads. Assessments were performed on structures to predict building damage due to wind loads ranging up to hurricane events. The performance design utilized the modeling of two key systems and their interactions between one another: a model describing the environment and wind parameters, and a model describing the structural system and its characteristics. The environment and wind parameters were considered as if there were no structure present. This type of wind model is labeled as a ‘free-field wind’. Wind parameters were site- dependant and included data such as: average wind velocity, turbulence ratio and intensity, and the statistical distribution of wind directions. The structural system was designed for typical service loads. Only gravity loads were considered during the initial design of the structure, and environmental loads were omitted. This allowed for the merging of these two systems into a system referred to as the ‘exchange region’. Using modern tools, these two systems were combined to determine the total system behaviour. Both structural and wind behaviour were analyzed to consider their effect on one another. 19 3.2.5 Guidelines for the Railcar Cover System Establishing performance based design guidelines for the cover system would utilize previous works completed by researchers for the performance based wind design of structures. A few key differences separate these two design guidelines, however. The cover system would analyze wind loads across a large site and wind speeds for a moving railcar convey change substantially based on the railcar travel speed and the wind speed and direction. Relevant wind speeds and angles of attack would be considered for the cover system, combining typical travel speeds and wind speeds to develop an understanding for apparent wind speeds relevant to analysis. DVs relevant to the client would represent the high and low performance requirements of the cover system based on requirements to ensure that safety, economic costs, and utility are optimized. For the railcar cover system, relevant DVs would include: • Service life span • Safety • System efficiency in reducing dust loss • It is recommended that a high and low performance tiers be established with regards to expected railcar cover performance under standard wind loads and wind storm events respectively. Steps can then be taken to evaluate the probabilistic nature of wind loads. By addressing the uncertainty of wind loads, wind storm events can be categorized by intensity and return periods. This would allow the assignment of wind intensities to expected railcar 20 cover performance. However, due to the large site in which the wind hazard must be analyzed and the dynamic nature of the railcar (with travel speeds combining with wind speeds for a variety of wind speeds), this method of categorizing wind loads based on probability of occurrence may be difficult to implement. After the establishment of probabilistic wind loads and established performance levels, structural response for each level of loading can be determined. By investigating structural behaviour, relevant EDP can be determined, these parameters should include: • fatigue stresses • railcar cover displacements • latch stresses and displacements. DMs would be established by creating threshold limits for these EDP. These DMs relevant to EDP measurements would then be related to performance requirements established by DVs. For instance: fatigue stress thresholds would be limit fatigue stresses to survive under a large number of loading cycles without excessive structural degradation. In summary, the construction of performance guidelines for the cover system should utilize various analysis tools to appropriately describe the railcar cover system behaviour and performance under varying load conditions. These tools would analyze wind hazards, relate them to structural performance, and seek methods in which their performance can be related and measured against relevant performance criteria established by stakeholders. An example of a performance guideline for the cover system is listed below. 21 Table 3.2 Performance Guidelines for Railcar Cover System Performance Guidelines Level Frequency of Wind Event Performance Level EDP DM 1 90% Full Serviceability Fatigue Stress, Cover Displacement maximum stress: 50% of yield stress; maximum cover displacement: 0.5inch 2 10% Partial Serviceability maximum stress: 75% of yield stress; maximum cover displacement: 1inch 3 <1% Survival Maximum Latch Stress, Maximum railcar cover Rib Stress maximum latch stress: 90% of latch fracture stress; maximum railcar cover rib stress: 80% of fracture stress Relevant to the establishment of EDP for the cover system, the use of CFD solutions have been suggested. The CFD analysis would become a tool in determining the environmental information and aid in the provision of loads necessary for the completion of the structural analysis. 22 Chapter 4: Computational Fluid Dynamics 4.1 Fluid Dynamics Fluid dynamics is the study of fluid motion and its properties throughout its flow. Fluid flow is often difficult to visualize due to the numerous properties that interact with one another within the fluid flow. Turbulence is also a phenomenon that changes the properties of the fluid flow to large degrees. Turbulence occurs when a fluid velocity reaches ranges where a laminar and predictable flow is near impossible. This phenomenon is typically described as having rapidly varying velocity and pressure at any given point. Several principles exist that describe the fluid flow through principles such as conservation of momentum and energy. The most common principles are the Bernoulli’s and Navier Stokes. These principles utilize common laws of physics to describe the state and flow of the fluid. 4.1.1 Bernoulli’s Principle Bernoulli’s Principle utilizes the physics principle of ‘conservation of energy’ and establishes a constant at which most points of a fluid flow may be evaluated upon. The principle states that there is a strict relationship between velocity, pressure, and elevation for every point in the fluid flow. As velocity increases (interpreted as kinetic energy), then a proportionate decrease in pressure and/or elevation must be observed (interpreted as potential energy). Bernoulli’s principle’s applications are numerous but lose its effectiveness as specific parameters exceed the established thresholds considered for ‘ideal fluids’. 23 As fluids reach excessive speeds, the use of Bernoulli’s principle loses traction. It is a general rule that the principle is applicable to slow gas flows of speed under Mach 0.3. The Mach number is a dimensionless ratio that relates the speed of a fluid flow or object to the speed of sound. As gasses reach speeds in excess of Mach 0.3 (or 102.1m/s), the fluid can no longer be categorized and purely adiabatic (without the gain or loss of heat). This principle is utilized to determine the validity of data presented by the CFD analysis and can indicate the level of reliability a specific analysis holds by comparing the Bernoulli’s constant across several points in a specific flow line. 4.1.2 Navier Stokes Navier Stokes is a physics equation coined by Claude-Louis Navier and George Gabriel Stokes that describes the motion of fluid substances. The equation is based off of Newtons’ second law in which force applied can be directly related to an object’s mass and acceleration. These principles are then applied to draw a relationship between inertia properties (accounting for unsteady and convective acceleration) and the divergence of stress (including pressure gradient and fluid viscosity) to describe the velocity field of a flow. The general form of the Navier Stokes equation is as follows: Equation 4.1 Navier Stokes Equation 24 The simplified Navier Stokes equation relies on idealistic parameters such as Newtonian fluids; this ensures that the simplified rules conservation of moment and mass apply. A Newtonian fluid is such that the stress and strain of the fluid is linearly related upon one another and consists of a viscosity that depends only on the temperature and pressure on the fluid. The simplified version of the Navier Stokes principle also requires that the fluid be incompressible. It is assumed that by ensuring fluid incompressibility, unpredictable phenomenon such as sound and shockwaves can be avoided. The ability of the Navier Stokes equation to map a velocity field that describes the flow field of a fluid allows for the iterative process of solving a steady state solution through computation intensive procedures. The use the CFDesign computation program and the Navier Stokes principle allows for the determination of the velocity field and enables the possibility of calculating flow parameters such as velocities and pressure. The program also aids in the visualization of flow-lines and most importantly, can determine pressure distributions on a variety of geometries. 4.2 CFD CFD is a field of analysis that utilizes numerical methods to simulate fluid flow conditions. These numerical methods allow the use of computation programs to provide numerous iterations of a flow principle and equation such that a steady state solution can be found that accurately describes the flow field. The properties capable of being determined from the flow field include velocity fields, temperature gradients, and points of pressure along the flow profile. Often utilized is the Navier Stokes equation where field of fluid flow 25 is iterated multiple times to yield convergence towards an acceptable solution. Each solution is reached by establishing relevant geometric data such as physical restraints and boundary conditions. The physical restraints are provided by a geometric parasolid model and the boundary conditions are used to establish initial flow conditions as well as inlet and outlet flows. Previous CFD analyses for the cover system were completed by STX Europe in 2009. The report calculated maximum wind pressure on the train considering angles of attack at 90 degrees, 0 degrees, and 29 degrees to the direction of travel. Wind velocities were calculated at 50mph (22.35m/s) and 90mph (40.233m/s). Apparent winds speeds were higher due to railcar travel speeds. The average pressure over the surface was calculated for each load case and was utilized for a static finite element analysis. This study focuses on expanding and the modeling conducted by STX Europe to develop a broader scope of knowledge held regarding CFD modeling for railcar systems. The program CFdesign was used for all of the modeling conducted in this study. CFdesign is an Autodesk paired software that utilizes the parasolid elements (file extension .x_t) from Autodesk Inventor to create and the model geometry. These parasolid elements aid in establishing physical restraints for the CFdesign software to utilize. CFdesign is capable of providing fluid flow and thermal simulations, and offers various meshing tools to improve accuracy and speed of the simulations as required. Basic procedures involved in the flow modeling include three phases: preprocessing, simulation, and postprocessing. 26 4.2.1 Stages of CFD Analysis The preprocessing phase involves the establishment of model geometries (the railcar and cover system for this study). The geometry establishes physical boundaries with which the proposed flow can interact with. A volume is created to provide information upon which spaces within the model are occupied by the modelled fluid. Additional information concerning physical conditions such as temperature and radiation can also be accounted for. Boundary conditions are then established to directly influence the fluid behaviour and properties of the modelled space. The simulation phase involves the reiteration of the flow solution by evaluating relationships established by the Navier Stokes equation in a modeled space. The iterations are conducted until convergence or a steady state solution is achieved. Various methods of discretization are available for use during the simulation phase of the CFD Analysis. These include the finite volume method (discrete control volumes), finite element method, finite difference method, spectral element method, and the boundary element method. CFdesign software is capable of modeling a variety of flow profiles including laminar flow and various configurations for turbulent flow. Turbulence models available include: k- epsilon, Eddy Viscocity, RNG, Mixing Length, and Low Re K-epsilon. For the purpose of this study, the default k-epsilon turbulence model was used for flow simulation. 27 The post processing phase utilizes a postprocessor to produce an analysis and visualization of the solution achieved from the simulation phase. CFdesign is capable of providing several analytical tools during the postprocessing phase. These tools allow the visualization of flow lines around the geometry, the measuring of velocity magnitudes and vectors, and the measurement of static pressures along the three major axes. These tools enable designers to draw comparisons between geometric configurations and models as well as provide geometry response to the applied wind loading. Figure 4.1 Flow Line Visualization for Railcar and railcar cover with 90 degree angle of attack Source: Generated using CFdesign 4.2.2 Model Preparation 4.2.2.1 Autodesk Inventor All model geometries were composed using the Autodesk Inventor software. The railcar model was created from existing model components from a previous study completed by Fridriksson. The cover system was created in Autodesk Inventor to reflect the updated 28 geometric of the cover system. Original railcar cover models included the inclined surfaces at the ends of the cover system but did not include the extension of the cover over top of the inclines. Autodesk Inventor was then used to export models into a parasolid element that could be used for analysis in various modeling programs. Parasolid elements provide a geometrical shape including advanced surface information such as thickening and thinning properties. These elements can be utilized by various analysis programs such as ANSYS (for finite element modeling) as well as CFdesign (dynamic flow modeling). Figure 4.2 Railcar Cover Model used for Analysis Source: Generated from Autodesk Inventor 29 4.2.2.2 CFdesign Software CFdesign is a modeling program that is capable of utilizing physical geometries and analyzing fluid flow through and around an object. It is commonly used for solving thermal and convectional flows through closed piping systems and mixing body problems, however, the use of the program for fluid structure interaction is also possible through the establishment of external fluid volumes surrounding the model geometry. CFdesign provides all the necessary tools required to conduct a flow investigation: preprocessing, simulation, and postprocessing. External volumes allow for CFdesign to define an enclosed rectangular element to surround the model. This external volume is adjustable by size and orientation to ensure that the wind flows appropriately reflect the modeling conditions required for a specific model and load case. These external volumes can be assigned boundary conditions as required to accurately reflect flow conditions. 4.2.2.2.1 Solution to Angle of Attack problem Initial efforts to introduce angles of attack to the wind models yielded several possible solutions. The first solution included the establishment of multiple inlet boundary conditions. It was proposed that by combining and two adjacent external volume faces and adjusting velocities appropriately it would be possible to introduce variations in angles of attack. 30 This methodology fell short as measured flow velocities for the validation model did not agree with theoretically established values. The validation model featured external volume faces where flow velocities were defined to be 1 metre per second (m/s). It was theorized that double inlet conditions would feature flow velocities at a combined vector of 1.4 m/s. The rectangular nature of the external volumes led to flow velocities of up to three times larger than expected values, and an uneven distribution of wind velocity throughout the model. The solution to this problem was to maintain single inlet and outlet flows through model geometries with a single angle of attack. The angles of attack could be coarsely adjusted by rotating the external volume to angle a face normal to the required angle of attack. This method allowed the fine tuning of angles of attack to 0 degrees and 90 degrees with standard geometry models. An angle of attack of 45 degrees was also introduced, as it was the only rotation in external geometry that could be consistently replicated through all models. The 45 degree angle of attack was created by utilizing view port tools available by the CFdesign software and aligning the external volume against the viewport to accurately reproduce a 45 degree rotation in the external volume. This rotated external volume enabled the modeling of the railcar and cover system with an additional angle of attack to consider. 31 4.2.2.2.2 Boundary Conditions CFdesign is capable of describing numerous boundary conditions. These boundary conditions aid in the initialization of flow properties and enable the definition of wind loading conditions. Used in this study are the following boundary conditions: velocity, pressure, and slip/symmetry. Velocity is utilized to signify an inlet flow. Flow velocities travel in a direction normal to the defined plane. These velocities can range from metres per second to kilometres per second (km/h). The defining of these velocities creates the basis of load condition variations for the models. Outlet faces were defined using a pressure designation. Following Bernoulli’s principle of a direct relationship between pressure and velocity, the definition of an outlet with a static pressure of 0 signified that the face would become an outlet for the flow to escape the model. Similar to wind tunnel simulations and analysis cases that feature a closed pipe system, Bernoulli’s principle signify outlet flows as having converted all embodied energy into kinetic energy; eliminating all pressure effects such that flow velocity is at full capacity. 32 Figure 4.3 Boundary Conditions for Railcar and Railcar Cover Model Source: Generated by CFdesign 4.2.2.2.3 Materials CFdesign is capable of modeling a variety of materials. These materials aid methods that use the material properties to provide accurate details regarding fluid and structure response. Boundary layer conditions change between materials as variations in material surfaces provide a different fluid-solid interaction zone. In addition, variations in materials also provide different solutions for thermal convection simulations. Materials are typically assigned as physical substances and typically fall into two categories: fluids and solids. Although these two material components are most commonly used, other material distinctions exist. Distributed resistances represent materials that distort fluid flow such as baffles or geometry with a large number of holes; distributed resistances also enable the modeling of permeable elements with the ability to define free area ratios. Another material, 33 surface parts allow for the modeling of thin 2D geometries without creating excessively large models by meshing thin solid elements. Figure 4.4 CFdesign Material Distinctions Source: Generated using CFdesign The materials used by the modeling of the railcar and railcar cover are primarily geometric centric. These 3D elements were divided into three sections: the external volume enclosing the model, the railcar, and the railcar cover. The external volume material is defined as a fluid with the properties of air to simulate wind conditions. The railcar was defined as a solid aluminum material. The cover system is originally designed as a Glass Reinforced Plastic material, however in the absence of this material option, a PCB Plastic for Laminate material was chosen. Both these materials share a plastic surface and it was found that the material selection was not of great importance in the modeling as model geometry played the largest role for model accuracy. 34 4.2.2.2.4 Mesh Size CFdesign modeling software divides each model into individual elements that are collectively referred to as a mesh. For three dimensioned models and solids, each element is divided into a tetrahedral with four nodes (an object with four sides and has a triangular shape). For two dimensioned objects, each element is divided into triangular elements with three nodes. Figure 4.5 Mesh Shapes for 3D and 2D Objects in CFdesign Source: CFdesign Online Help 2011 The meshing capabilities of CFdesign were severely limited by hardware and operating system capabilities. It was determined through extensive trial and error that element counts upwards of one million could not be run by the CFdesign software. Meshing is categorized into two options for CFdesign: Manual and Automatic. The manual meshing model allowed for individual solids (such as the isolating of a single railcar component) to be manually meshed with element size specifically defined. This method allows for the careful specification of each component of the model. Components where finite details must be carefully considered can benefit from this tool as important model characteristics can be focused while larger more cumbersome model components 35 where the fluid interaction is of less importance can be meshed with a larger element size. The benefits of efficiently allocating element sizes to individual components are that total element countS can be reduced, thus creating a model that can be run faster given its specific geometry. The disadvantages of utilizing a manual meshing mode is that the time required to individually build the meshes for each model can be quite taxing. Complicated models with large numbers of components can require substantial amounts of time to individually specify element sizes. The automatic meshing CFdesign tool breaks down individual model components. Components are separated and assigned appropriate mesh sizes according to their shape and size. Mesh enhancement options are also available for the automatic meshing tool. CFdesign enables users to determine the number of mesh layers that are completed, as well as the layer thicknesses. Mesh layer count range from one to five, and mesh thicknesses can range from 0.01 to 1.2. These mesh enhancement options can provide more accurate flow profiles and read outs, although this is not proven. The effect of mesh data on the accuracy of models not well understood, and direct correlation should be confirmed through the use of scale testing under wind tunnel conditions or other simulation methods. For this study, the automatic meshing tool was used for all models, with the number of mesh layers set at 3 and the mesh layer factor set at 0.15. 36 Figure 4.6 Railcar and Railcar Cover System Fully Meshed Source: Generated using CFdesign Validation models were completed for these mesh enhancement options. A double railcar model was analyzed using a range and combination of mesh layer counts and layer thicknesses. It was determined that additional tests should be completed to determine the most accurate meshing parameters. All models exhibited similar flow profiles and velocity distributions at segments around the gap of the second railcar where measurements were made. Velocities did not show consistency throughout the models. Pressure measurements demonstrated a high level of confidence however, as all pressure readings followed agreeable trends across all models. 4.2.2.2.5 Solving Following the completion of the preprocessing phase of CFdesign, a solver program was used to execute the flow simulation. The solver program used is embedded within CFdesign and contains several options to aid in the modeling of the flow. Iteration counts can be controlled to adjust the amount of iterations required to reach convergence (a stable solution) of the Navier Stokes equations. Other options included the selection of flow from 37 laminar and turbulent models; a standard turbulent model of epsilon-k was used for this study. 4.2.2.2.6 Results The postprocessing phase of dynamics fluid modeling is conducted using analysis tools embedded within CFdesign. These tools allow the measurement of flow specifics such as velocity magnitudes and static pressures in all three major axis directions as well as providing three dimensional visualizations of flow lines and the velocity field. 38 Chapter 5: CFdesign Models Several models were completed including single and double railcar models. Hardware limitations led to the establishment of these two models as a model type with three railcars could not be processed. As a result, a medley of single railcar models and double railcar models were analyzed under similar conditions. All models were exposed to an identical set if wind load velocities and directions. Data presented regarding static pressures and velocity magnitudes were all measured at identical locations. 5.1.1 Single Railcar Models The single railcar models featured several variations. An open railcar [Rc] was modeled to demonstrate the current standard for bulk coal carts with no cover system in place. Velocity measurements for this model were taken with the aid of a planar element across the top of the railcar. An average velocity was measured both in the y-direction (direction in and out of the car vertically) and total velocity magnitude was also measured. To contrast with this original model and to demonstrate the effectiveness of a cover system, railcar models with the cover system was also modeled. The railcar and cover system models represented three variations in geometry, all with differing railcar to railcar cover gaps. The designer proposed a gap distance of 5/8 inches (0.625 inches) and models with gap distances of 0.5 inches and 1 inch were also conducted to investigate the effect of railcar cover displacements on flow rates. The labeling of these railcar and cover systems were as follows: railcar with cover system with a 0.5 inch gap [RcCG0.5], railcar with cover system with a 5/8 inch gap [RcCG0.625], and the railcar with cover system with a 1 inch gap [RcCG1]. 39 5.1.2 Double Railcar Models The double railcar models explored different configurations for successive railcars. Key details were provided by the designer for the model selection of this study. The gap between successive railcars was defined to range between 28 inches and 40 inches, and a 24 inch shutter was proposed to be installed at the end of railcars to possibly reduce drag forces. Relevant to the designer’s interests, carts including a 28 inch and 40 inch gap from cart-to- cart were analyzed, as well as the inclusion of a 24 inch shutter attached to the end of first railcar (in the direction of proposed travel). The railcar model used for these studies was the railcar with a 1 inch gap, although a model including the 5/8 inch gap was also included to compare any discrepancies between models. Figure 5.1 Shutter Attached to End of Railcar (Elevation View) Source: Generated using Autodesk Inventor 40 Figure 5.2 Shutter Attached to End of Railcar (Plan View) Source: Generated using Autodesk Inventor These models were analyzed for flow rate as well as cover pressure distributions given wind speeds of 1 metres per second (1m/s), 10 metres per second (10 m/s), and 100 kilometres per hour (100km/h). Speeds were chosen based on the railcar speed during handling, regular travel, and high speed travel. Angles of attack (wind direction) for the all railcar models were completed at 0 degrees (parallel to the direction of travel), 45 degrees, and 90 degrees (perpendicular to the direction of travel). All three angles of attack were utilized for all wind speeds with the exception of the 90 degree yaw angle, which did not feature the 100km/h wind speed. 41 Figure 5.3 Angles of Attack Source: Generated using CFdesign 5.2 Flow Rates Flow rates were calculated by postprocessing flow data for each railcar model. Velocity magnitude measurements were taken across the gaps of all railcars, with designations of the: front, left, right, and rear side taken for each railcar to differentiate between the four faces of the railcar during travel. Along each edge, measurements were made in the mid distance of the gap between the railcar and the cover. 42 Figure 5.4 Railcar Orientation Labels Source: Generated using CFdesign Figure 5.5 Graphing Lines for Velocity and Pressure Measurements Source: Generated using CFdesign 43 Figure 5.6 Graphing Lines for Velocity and Pressure Measurements (Elevation View 1) Source: Generated using CFdesign Figure 5.7 Graphing Lines for Velocity and Pressure Measurements (Elevation View 2) Source: Generated using CFdesign 44 These points were mapped using the following coordinates (which were extrapolated from the model). Table 5.1 Graphing Points used for Velocity and Pressure Measurements P oint x y z C ar t 1 A - 7.28 3 .97 1 .5 B 7 .27 3 .97 1 .5 C 7 .27 3 .97 - 1.5 D - 7.28 3 .97 - 1.5 P oint x y z C ar t 2 E - 22.78 3 .97 1 .5 F - 8.23 3 .97 1 .5 G - 8.23 3 .97 - 1.5 H - 22.78 3 .97 - 1.5 5.2.1 Single Railcar Models Single railcar models were analyzed to compare the flow rates for variations in cover to railcar gaps. A standard railcar without the cover system was also analyzed to compare the degree of benefits expected from the cover system. The railcar model without the cover system exhibited extremely heavy flow rates. The flow profiles within this model may not be completely accurate as a railcar fully loaded 45 with coal would interact with the wind flow differently. The values provided by this empty railcar were measured using an average velocity across the open face of the railcar. An average of the velocity magnitudes were taken for all the points. This average was then used to determine the average flow rate across the open railcar. Figure 5.8 Mesh of Graphing Lines for Velocity and Pressure Measurements for Open Railcar Source: Generated using CFdesign For the railcar and cover system models, velocity was measured along the gaps between the railcar and the cover. Steps were made to differentiate between the front of the railcar, the sides, and the rear. The front edge of the cart was defined to be the first edge of the railcar exposed to the wind flow. The right edge of the railcar was always exposed to 45 and 90 degree angles of attack first. These edges were defined to maintain consistency throughout the models and allow the determination of railcar orientation. 46 It was demonstrated that the cover system exhibits great advantages over the open railcar model, with flow rates between the inside of the railcar and the outside environment reduced to 1% with the installation of the cover for all wind speeds. Comparing angles of attack for the single railcar models, it was observed that the 0 degree and 90 degree angles of attack to exhibit the highest flow rates. In all cases, the measured flow rates for 45 degree angles of attack were lower by values ranging from 83% to 51% of peak flow rates. This phenomenon is most likely due to the odd geometry of the 45 degree oriented railcar that the flow must navigate around and through. Figure 5.9 Flow Rate Comparison between Single Railcar Models at 1m/s Wind speed Source: Data generated using CFdesign 47 Figure 5.10 Flow Rate Comparison between Single Railcar Models at 10m/s Wind speed Source: Data generated using CFdesign Figure 5.11 Flow Rate Comparison between Single Railcar Models at 100km/h Wind speed Source: Data generated using CFdesign 48 Table 5.2 Comparison of Flow Rates for Single Railcar Models Flow Rates 1m/s 10m/s 100km/h Rc 100% 100% 100% RcCG0.5 0.72% 1.09% 0.88% RcCG0.625 1.22% 1.24% 1.34% RcCG1 2.20% 2.48% 2.11% All models showed similar trends in data between angles of attack. Intuitively, it was expected that flow volumes would be highest in the model with the one inch gap between the railcar and lowest in the model with the half inch gap. This expectation was observed all models, with differences in flow rates between the smallest and largest gap being over three times (but having a gap width only two times larger). Comparing only the railcar and cover systems, the observed data continued to follow established trends. Figure 5.12 Flow Rate Comparison for Railcar to Cover Gap Distances at 1m/s Wind speed Source: Data generated using CFdesign 49 Figure 5.13 Flow Rate Comparison for Railcar to Cover Gap Distances at 10m/s Wind speed Source: Data generated using CFdesign Figure 5.14 Flow Rate Comparison for Railcar to Cover Gap Distances at 100km/h Wind speed Source: Data generated using CFdesign 50 Table 5.3 Comparison between Railcar to Cover Gaps at 1m/s Wind speed Flow Rates 1m/s 10m/s 100km/h RcCG0.5 32.91% 32.91% 32.91% RcCG0.625 55.42% 55.42% 55.42% RcCG1 100.00% 100.00% 100.00% Through this analysis, it can be shown that the addition of the cover system supports the designer’s intentions. Flow rates through the railcar were greatly reduced as expected and slight deviations in gap distance (from the originally proposed 5/8 inch gap) changed flow rates as expected. 5.2.2 Double Railcar Models The double railcar models were chosen to evaluate realistic industry conditions. The relevant model of each model was the second cart (or successive cart) as the initial front cart would break the wind. Relevant to this study is the successive cart which would represent majority of the carts in a convoy. Measurements were taken using the same method as done with the single railcar models. 51 Figure 5.15 Flow Rate Comparison for Double Railcar Configurations at 1m/s Wind speed Source: Data generated using CFdesign Figure 5.16 Flow Rate Comparison for Double Railcar Configurations at 10m/s Wind speed Source: Data generated using CFdesign 52 Figure 5.17 Flow Rate Comparison for Double Railcar Configurations at 100km/h Wind speed Source: Data generated using CFdesign Comparing the maximum flow rates of each model at specific wind speeds: Table 5.4 Flow Rate Comparison for Double Railcar Configurations Flow Rates 1m/s 10m/s 100km/h 2RcCG0.625 G28in 63% 72% 72% 2RcCG0.625 G28in S24in 56% 48% 48% 2RcCG1 G28in 79% 90% 90% 2RcCG1 G28in S24in 92% 93% 93% 2RcCG1 G40in 100% 100% 100% Between the different angles of attack, it is observed between all models that the 90 degree angle of attack exhibits the highest flow rates whereas the 0 degree angle of attack exhibits the lowest. This is most likely due to the exposed nature of the 90 degree angle of attack. Both the 45 degree and 0 degree angles of attack present geometry that is difficult for the wind flow to enter and exit the railcar. 53 Table 5.5 Flow Rate Comparison for Installation of Shutter in 0.625 inch Railcar to Cover Gap Model Flow Rates 0.625 in Shutter 0 deg 1m/s 59.11% 45 deg 1m/s 56.94% 90 deg 1m/s 89.03% 0 deg 10m/s 62.37% 45 deg 10m/s 79.84% 90 deg 10m/s 66.80% 0 deg 100km/h 122.20% 45 deg 100km/h 64.20% Analyzing the data, it is apparent that flow rates tend to favour the installation of the data. This trend becomes less apparent as the railcar to cover gap increases from 0.625 inches to 1 inch. With this 60% increase in railcar to cover gap distance, patterns become more difficult to recognize. This may be due to errors in analysis and unstable flow solutions proposed by CFdesign. Flow rates seem to lack any bias towards the inclusion or exclusion of the 24 inch shutter. Table 5.6 Flow Rate Comparison for Installation of Shutter in 1 inch Railcar to Cover Gap Model Flow Rates 1in Shutter 0 deg 1m/s 117.70% 45 deg 1m/s 82.67% 90 deg 1m/s 116.32% 0 deg 10m/s 131.80% 45 deg 10m/s 80.01% 90 deg 10m/s 102.49% 0 deg 100km/h 32.70% 45 deg 100km/h 78.77% 54 Comparing the models where there is variation in successive cart gap, there is no discernible pattern between the two systems. The double railcar systems of railcar to cover gap distance 1 inch were compared with varying successive cart-to-cart gaps. Between the 28 inch gap and 40 inch gap models, there is no pattern that favours one design over the other. At lower speeds, it appears as if the 40 inch gap is at a disadvantage for flow rates but as demonstrated in the following section, presents an advantage in terms of pressures. This pattern quickly vanishes as wind speeds are increased. At 100 km/h wind speeds, the 40 inch gap distance is an at advantage, with flow rates lower by up to 50% for a 0 degree angle of attack. Table 5.7 Flow Rate Comparison for Increase from 28 inch to 40 inch Cart-to-Cart Gap Model Flow Rates 1in 40in Gap 0 deg 1m/s 184.97% 45 deg 1m/s 76.76% 90 deg 1m/s 125.86% 0 deg 10m/s 231.09% 45 deg 10m/s 58.91% 90 deg 10m/s 110.50% 0 deg 100km/h 49.63% 45 deg 100km/h 95.88% 5.3 Pressures Pressure distributions were taken across the cover of second cart. The labeling of the cover was separated each cover into five components: front and rear inclines, front and rear tops, and the top covers of the middle segment. Average pressure across the face of each component was measured and reported by the CFdesign program. 55 Figure 5.18 Cover Segments for Pressure Designation Source: Generated using Autodesk Inventor Railcar cover pressures were compared between the different models. Absolute maximums were taken for the front and rear inclines as well as all segments of the top of each cover. These values were aggregated into two categories for pressure measurements: the inclines (front and rear), and the tops (front, rear, and mid). The top segment of each cover model was divided into nine segments. The rear and front accounted for two segments while the remaining seven were categorized as mid segments during data measurements. Due to the limits states design focus of the cover performance, only maximum pressures were recorded for each cover segment. 56 Figure 5.19 Cover Pressure Comparisons for Double Railcar Configurations at 1m/s Wind speed Source: Data generated using CFdesign Figure 5.20 Cover Pressure Comparisons for Double Railcar Configurations at 10m/s Wind speed Source: Data generated using CFdesign 57 Figure 5.21 Cover Pressure Comparisons for Double Railcar Configurations at 100km/h Wind speed Source: Data generated using CFdesign Pressure distribution data demonstrates that the Top of the cover (front, rear, and mid) contain the highest magnitudes of pressure. This is most likely due to the cover geometry presenting a direct obstacle for the wind to flow past. In some cases, average pressures on segments of the Top cover were nearly twice that of the inclines. Some data anomalies are left unexplained through the analysis of this data. There lies no clear victor in terms of configuration of the different cover systems. At low wind speeds of 1 m/s, pressures range up to two times. At moderate wind speeds of 10 m/s, pressures can range by up to four times. And At high wind speeds of 100 km/h, pressures only range by less than two times (with the exclusion of anomalies/outliers). Comparing flow rates and average cover pressures between the different model types indicate a few observable patterns. However, these trends are not consistent for all cases. For the railcar and CoverFlex system with a cover to railcar gap of 0.625 inches, the flow rates 58 heavily favour the installation of the shutter. Flow rates are mostly reduced for all load cases with the installation of the 24 inch shutter at end of the leading cart. In some cases, these flow rate reductions are up to nearly 40%. This reduction in flow rate however is offset by an increase in cover pressures by up to 70%. Table 5.8 Pressure Comparison for Installation of Shutter in 0.625 inch Railcar to Cover Gap Model Pressure Shutter 0.625 in Top Incline 1m/s 149.66% 168.08% 10m/s 145.36% 170.00% 100km/h 116.46% 114.24% Comparing the models with and without the 24 inch shutter, it is clear that cover pressures are much higher with the inclusion of the shutter. This trend is observed at all wind speeds. Table 5.9 Pressure Comparison for Installation of Shutter in 1 inch Railcar to Cover Gap Model Pressure Shutter 1in Gap Top Incline 1m/s 124.04% 94.38% 10m/s 103.70% 64.95% 100km/h 85.53% 108.88% The trend indicating that shutters result in higher cover pressures becomes less apparent with the model gap with a 1 inch railcar to cover gap. The 1 inch railcar to cover gap model indicates that rather than observing a higher overall pressure throughout the entirety of the cover, the top of the cover experiences higher pressures with the shutter whereas the inclines experience a lower pressure. This reverses at high wind speeds as at 100 km/h wind speeds, the inclines experience a slightly higher pressure and the top of the cover 59 experiences a slightly lower pressure. Similarly a lack of patterns observed in flow rates between shutter and shutter-less models, pressure distributions also lack any clear pattern in which flow rates or pressure clearly favour the inclusion or exclusion of the shutter. Table 5.10 Pressure Comparison for Increase from 28 inch to 40 inch Cart-to-Cart Gap Model Pressure 40in gap 1in Gap Top Incline 1m/s 74.38% 62.14% 10m/s 48.44% 33.96% 100km/h 168.04% 145.66% For the two models of varying cart-to-cart length, it is observed that there is a slight advantage for the 40 inch cart-to-cart gap compared to the 28 inch cart-to-cart gap. Both models compared contained 1 inch railcar to cover gaps. Pressures for the cover attached to cart 40 inches behind the front cart are greatly decreased in both the inclines and the tops of the cover. This advantage disappears at high wind speeds however, as cover for the 40 inch cart-to-cart model experienced pressures more than 45% higher than that of the 28 inch cart- to-cart gap cover model. A correlation between wind pressure and flow rates is observed in most models. When comparing models with slight variations in geometry, it is observed that advantages in flow rates are often offset by disadvantages in average cover pressure. This pattern can be recognized in the comparisons between the shuttered and shutter-less variations of the 0.625 inch railcar to cover gap models as well as the comparisons between the 28 inch and 40 inch cart-to-cart gap variations for the 1 inch railcar to cover gap models. 60 Although some patterns can be recognized from the comparison of these models, it is apparent that the discrepancies often occur at higher wind speeds. The differences in performances due to wind speeds must be considered when determining a threshold performance for each cover design pending on the railcar convoy geometry and parameters. At higher wind speeds, it should be noted that turbulent flows become more rampant and frequent. As the wind flows become difficult to predict, pressure distributions and flow rates may become harder to determine. 61 5.4 Validation Models Several validation models were completed to attempt to understand the modeling procedures conducted by the CFdesign software. These validation models explored several scenarios including: inlet and outlet parameters, meshing parameters, and model iteration counts. 5.4.1 Inlet and Outlet Parameters Inlet and outlet parameters were explored to investigate a method in which variations of yaw angles could be produced. For a square geometry element, a method was proposed where a combination of two adjacent external volume faces could be combined to form a single wind attack angle in one direction. External volumes typically form a six-sided rectangular enclosing element around the model geometry and utilize the sides to specify boundary conditions. All previous models used a single direction of flow, which is defined through one inlet face normal to the direction of wind and one outlet face on the opposite side of the external volume. The validation model geometry used a tear drop geometry that would be enclosed by a rectangular external volume. 62 Figure 5.22 Inlet Outlet Validation Model Source: Generated using Autodesk Inventor This tear drop geometry was then enclosed in an external volume using the CFdesign software. A variety of boundary condition combinations were explored. The combinations of inlets and outlets were as follows: 63 Table 5.11 Inlet Outlet Validation Model Parameters Elements Model Inlets Outlets Slip/Symmetry A 1 1 4 B 1 5 - C 1 - 5 D 2 1 3 E 2 2 2 F 2 4 - G 3 1 2 H 3 2 1 I 3 3 - Figure 5.23 Colour Code for CFdesign Boundary Conditions Source: Generated using CFdesign Figure 5.24 Inlet Outlet Validation Boundary Conditions - Model A Source: Generated using CFdesign 64 Figure 5.25 Inlet Outlet Validation Boundary Conditions - Model B Source: Generated using CFdesign Figure 5.26 Inlet Outlet Validation Boundary Conditions - Model C Source: Generated using CFdesign Figure 5.27 Inlet Outlet Validation Boundary Conditions - Model D Source: Generated using CFdesign 65 Figure 5.28 Inlet Outlet Validation Boundary Conditions - Model E Source: Generated using CFdesign Figure 5.29 Inlet Outlet Validation Boundary Conditions - Model F Source: Generated using CFdesign Figure 5.30 Inlet Outlet Validation Boundary Conditions - Model G Source: Generated using CFdesign 66 Figure 5.31 Inlet Outlet Validation Boundary Conditions - Model H Source: Generated using CFdesign Figure 5.32 Inlet Outlet Validation Boundary Conditions - Model I Source: Generated using CFdesign This validation study determined that that it is infeasible to use multiple inlets and outlets to simulate different angles of attack. Measurements were made for each model type for a velocity graph along the edge of the as well as a single point velocity. 67 Figure 5.33 Inlet Outlet Validation Study - Graphing Line used for Velocity Measurements Source: Generated using CFdesign Figure 5.34 Inlet Outlet Validation Study Velocity Graph - Single Inlet Source: Data generated using CFdesign 68 Figure 5.35 Inlet Outlet Validation Study Velocity Graph - Double Inlet Source: Data generated using CFdesign Figure 5.36 Inlet Outlet Validation Study Velocity Graph - Triple Inlet Source: Data generated using CFdesign 69 Velocity graphs demonstrated a large level of variance in each model type. Models were categorized for the number of 1 m/s inlet boundary conditions they contained. There were three types of models, single inlet models, double inlet models, and triple inlet models. Additionally to these velocity graphs, a velocity magnitude measurement was made at a single point on the upper corner near the inlet faces. This point of measurement can be seen as “P1” in the figure below. Figure 5.37 Inlet Outlet Validation Study - Measurement Point Source: Generated using CFdesign 70 Figure 5.38 Inlet Outlet Validation Study - Point Velocity Comparison Source: Data generated using CFdesign Figure 5.39 Inlet Outlet Validation Study - Point Velocity Comparison (Without Model C) Source: Data generated using CFdesign Prior to this validation experiment, it was proposed that velocity magnitudes should follow a standard square root sum of squares method to derive the expected velocity. This 71 method of combining velocities of 1m/s for a single inlet, 1.41m/s for two inlets, and 1.73m/s for three inlets. The inclusion of multiple inlets was not a satisfactory solution in introducing angles of attack to the model. This is due to the method in which flow volumes are introduced into the model. With two adjacent inlet faces, the flow profile is effects the model in a parabolic shape rather than combining into a single angled inlet face. Figure 5.40 Inlet Outlet Validation Model - Flow Visualization for Triple Inlet Model Source: Generated using CFdesign Through this validation study, it was understood that the sole method of introducing angles of attack to a model would be through the rotation of the external volume. 72 5.4.2 Mesh Sizes A variety of mesh sizes were also explored to determine whether different layers of meshing would affect results. CFdesign offers numerous meshing parameters for both automatic and manual meshing methods. Focusing on varying the automatic meshing method, efforts were made to understand the effect of layer enhancement parameters. A validation model was created using the geometry from the single railcar model with a railcar to cover gap of 5/8 in. This model was exposed to a single inlet flow condition with wind speed velocity of 10 m/s and an angle of attack of 0 degrees. The various conditions analyzed altered several parameters such as the number of mesh layers created during the meshing of the elements. Another parameter altered was the mesh layer enhancement factor, which determined the thickness mesh layers. Mesh parameters that were analyzed included a combination of varying number of layers (1 to 5) and layer factors (0.1, 0.5, and 1). Two extra models included in the analysis utilized the ‘automatic layer adaptation’ option and one model was run with 200 iterations steps rather than only 100. Some models did not run successfully due to the complicated nature of the model, meshing errors resulted in program errors and several 1.0 layer factor models were not successfully simulated. Models were labeled to represent their meshing conditions: [10ms 0deg L 0.1F] represented a model with a 10 m/s wind speed, 0 degree angle of attack, contained 1 Layer, and a layer factor of 0.1. 73 Figure 5.41 Mesh Size Validation - Velocity Measurements (All) Source: Data generated using CFdesign Figure 5.42 Mesh Size Validation - Velocity Measurements (Only Layer Factor 0.1) Source: Data generated using CFdesign 74 Figure 5.43 Mesh Size Validation - Velocity Measurements (Only Single Layers) Source: Data generated using CFdesign Figure 5.44 Mesh Size Validation - Pressure Measurements (All) Source: Data generated using CFdesign 75 Figure 5.45 Mesh Size Validation - Pressure Measurements (Only Layer Factor 0.1) Source: Data generated using CFdesign Figure 5.46 Mesh Size Validation - Pressure Measurements (Only Single Layer) Source: Data generated using CFdesign Velocity graphs showed a general trend in data, although pressure graphs were more consistent. This shows that changes in meshing parameters will lead to drastic changes in flow velocity field solutions. This is most likely due to the great effect the meshes have on 76 the method in which the railcar and cover geometry interacts with the wind flows under differing mesh conditions. 5.4.2.1 Layer Adaptation Figure 5.47 Mesh Size Validation - Velocity Measurements (Layer Adaptation) Source: Data generated using CFdesign Figure 5.48 Mesh Size Validation - Pressure Measurements (Layer Adaptation) Source: Data generated using CFdesign 77 Comparing the effect of layer adaptation leads to the understanding that there is little to no effect of layer adaptation on flow velocities and the velocity field solution presented by CFdesign. 5.4.2.2 Iteration Count Figure 5.49 Mesh Size Validation - Velocity Measurements (Iteration Count) Source: Data generated using CFdesign Figure 5.50 Mesh Size Validation - Pressure Measurements (Iteration Count) Source: Data generated using CFdesign 78 The effect of number of iteration steps allowed for a simulation also presented very little effect on the velocity field solution presented by CFdesign. This is most likely due to the convergence of the solution being reached within iteration steps lower than 100. Pressure graphs however difference quite largely between these two models. Model and solution convergence plays a large role in model accuracy. As the Navier Stokes equation is iterated, larger numbers of iterations ensure that a satisfactory solution can be reached by ensuring convergence occurs. 5.4.2.3 Convergence Convergence graphs indicate the stability of the solution solved by CFdesign. As the CFdesign software uses numerous iterations of the Navier Stokes equation to find a stable solution for the velocity field problem that each model presents, the convergence graph is the best indicator of a coherent and accurate solution. Convergence is typically described as the rate of change in which a solution changes from iteration to iteration. Visualized with a graph in CFdesign, an accurate solution that has reached convergence would feature a graph whose slopes at later iterations reach a near horizontal slope. This would indicate that additional iterations would yield the same solution, and that a stable solution has been found. Models were run initially in succession, with new model loading conditions utilizing the end state of previous loading scenarios. This method of CFD simulation led to inaccurate 79 and misleading results, as noticed by outliers from otherwise trending data. Upon discovery, efforts were made to re-simulate models facing this problem. Analyzing the effect of convergence on a model can aid in the understanding of outlier information as well as nonconforming data. For the mesh size validation models, the velocities followed a trend, but did not agree with respect to velocity magnitudes. This is due to the non-converging state of many of the solutions. Figure 5.51 Mesh Size Validation – Convergence (Velocity) Source: Data generated using CFdesign 80 Figure 5.52 Mesh Size Validation – Convergence (Pressure) Source: Data generated using CFdesign This graph indicates that the solution of each of the velocities may have not reached the most accurate solution for the model. As a result, velocity magnitudes did not agree across all models. Pressure convergence graphs performed with much more consistency as shown by the convergence graph. This directly correlates with the level of consistency visible form the pressure graphs from the mesh size validation experiment. 81 Chapter 6: Conclusion 6.1 Performance Based Design The establishment of a performance based design guideline can aid in the future designs of all similar projects. By evaluating the needs of stakeholders and establishing working relationships between these needs and a products performance, it is possible to create more efficient designs that provide optimal levels of economic benefit and product utility. Relevant to the cover system, it is important to note that extensive analyzes should be conducted to determine the total cover behaviour and relevant wind hazard information. This analysis should address cover performance under damaged conditions and ensure that the cover system can perform as required under various ranges of loads from regular operation to wind storm events. Key themes that the performance guideline should address for the cover system include: • Safety • Reliability • Efficiency 6.2 Computational Fluid Dynamics Analysis Through the use of CFdesign fluid modeling software, comparisons were made for the cover system. These comparisons analyzed the various configurations available for the cover system and sought to provide insight upon differences and advantages between the various configurations. 82 6.2.1 Single Railcar Model A model consisting of a single railcar model analyzed the effectiveness of the cover system. It was found that flow rates were reduced to 1% between the models with and without the cover system. Additionally, models consisting of railcar to cover gaps of 0.5 inches, 0.625 inches (proposed design by the designer), and 1 inch were compared. As expected, flow rates were greatest in models with greater railcar to cover gaps. However, increases in railcar to cover gaps of 100% produced an increase in flow rate of 300%. This phenomenon demonstrates how great an impact a slight deviation on model geometry has on the flow profile. 6.2.2 Double Railcar Model A double railcar model was analyzed to compare flow parameters between various railcar configurations. These configurations included the installation of a 24 inch shutter at the end of the front railcar (for a cart-to-cart gap of 28 inches) and a 40 inch cart-to-cart gap. The proposed design utilizes a 24 inch gap from cart-to-cart and this model was used as a base for comparisons to be made. Parameters measured included velocities, flow rates, and pressures on the four exposed edges of the railcar. Additionally, cover surface pressures were measured to determine the effect of wind velocities on cover pressures and to compare the various configurations. It was found that some configurations exhibited an inverse relationship between flow rates and cover pressures. This pattern was only recognized in the comparison for the 0.625 83 inch railcar to cover gap models comparing flow rates and pressures with and without the shutter. On other models, this relationship was less obvious. No clear recommendations can be made regarding the benefits of the installation of the shutter. It was found that benefits in one performance category (ie. Flow rate, cover surface pressure) was offset by disadvantages in other categories. More research is recommended to determine whether a conclusive trend can be found that shows clear advantages of one design over the other. 6.2.3 Validation Study A validation study was conducted to determine the effects of model parameters on model results. The compared a variety of models constructed in CFdesign against one another, each with slight variations in meshing parameters (ie. Mesh size, Simulation iteration count). No conclusive evidence was available for comparison on the accuracy of the models, and it was found that the changing of mesh enhancement parameters severely changed the measured values in each model. Although there values did not agree, the trend and velocity profile of each solution agreed in shape and scale. Despite this obstacle with flow data confidence, all models were simulated using identical meshing enhancement options and parameters such that a valid comparison could be made between all the models. It is recommended that future studies seek to provide realistic data for comparison, such that the correct meshing parameters can be determined through empirical means. 84 References Autodesk®. (2011) Autodesk® Simulation CFD Help. Retrieved from http://www.cfdesign.com/OnlineHelp/2011/ Augusti, G., & Ciampoli, M. (2008). Performance-based design in risk assessment and reduction. Probabilistic Engineering Mechanics, 23(4), 496-508. doi: 10.1016/j.probengmech.2008.01.007 Ciampoli, M., Petrini, F., & Augusti, G. (2011). Performance-based wind engineering: Towards a general procedure. Structural Safety, 33(6), 367. doi: 10.1016/j.strusafe.2011.07.001 Fridriksson, J. (2011). Finite element analysis and cost/risk assessment of the flex cover system. University of British Columbia. Insitut Teknologi Sepuluh Nopember. (2008). Principles of Limit State Design. Retrieved from http://oc.its.ac.id/ambilfile.php?idp=1567 Kalay, Y. E. (1999). Performance-based design. Automation in Construction, 8(4), 395-409. doi: 10.1016/S0926-5805(98)00086-7 Khier, W., Breuer, M., & Durst, F. (2000). Flow structure around trains under side wind conditions: A numerical study. Computers and Fluids, 29(2), 179-195. doi: 10.1016/S0045-7930(99)00008-0 Lam, F., Murphy, M., & Yang, T. Y. (2012). Performance evaluation of prequalified steel seismic structural systems in canada. Lisboa. , 15 NAFEMS (2012) What is Convergence? Retrieved from http://www.nafems.org/resources/cfdconvergence/Page0/ 85 Natural Resources Canada. (2012) About Coal. Retrieved from http://www.nrcan.gc.ca/energy/sources/1205 Neale, R. A. Prescriptive or Performance: You Make the Call Retrieved from http://www.hospitalitylawyer.com/ Newsletters/ PrescriptiveorPerformance-PartI.pdf Paul, J. C., Johnson, R. W., & Yates, R. G. (2009). Application of CFD to rail car and locomotive aerodynamics. (pp. 259-297). Berlin, Heidelberg: Springer Berlin Heidelberg. doi: 10.1007/978-3-540-85070-0_25 Tachibana, S., Masuya, H., & Nakamura, S. (2010). Performance based design of reinforced concrete beams under impact. Natural Hazards and Earth System Science, 10(6), 1069-1078. doi: 10.5194/nhess-10-1069-2010 86 Appendices Appendix A Railcar Cover Drawings 87 88 Appendix B Railcar Drawings 89 Appendix C Results from CFdesign C.1 Data for Model 2RcCG0.625 G28in 2 Rail Cars 0.625 inch cover to cart gap 28 inch cart-to-cart gap Summary for Cart 2 Flow Rate (m^3/s) 0 degree Speed 1m/s 10m/s 100km/h Edge Front 0.012735 0.118056 0.085629 Left 0.031576 0.340691 0.491074 Right 0.029492 0.29203 0.412187 Rear 0.007322 0.078531 0.079943 Total 0.081125 0.829308 1.068832 Flow Rate (m^3/s) 45 degree Speed 1m/s 10m/s 100km/h Edge Front 0.014424 0.172962 0.468235 Left 0.081516 0.955139 2.428339 Right 0.068238 0.850699 2.368571 Rear 0.016172 0.183163 0.474778 Total 0.18035 2.161963 5.739922 Flow Rate (m^3/s) 90 degree Speed 1m/s 10m/s Edge Front 0.019675 0.208268 Left 0.1216 1.364342 Right 0.12142 1.39663 Rear 0.015594 0.182366 Total 0.27829 3.151605 90 Average Pressure (Pa) 0 degree Speed 1m/s 10m/s 100km/h Front Incline 0.0365831 3.5931 -94.5349 Front Cover -0.0400683 -3.97936 -121.998 Mid Cover -0.108313 -11.1511 -136.955 Rear Cover -0.102738 -10.4368 -133.857 Rear Incline -0.14021 -15.7677 -150.445 Average Pressure (Pa) 45 degree Speed 1m/s 10m/s 100km/h Front Incline 0.278418 29.8358 125.107 Front Cover 0.0684056 6.37289 -65.4024 Mid Cover -0.01 -2.30 -134.58 Rear Cover 0.335297 32.2313 111.8 Rear Incline 0.337338 33.0009 133.791 Average Pressure (Pa) 90 degree Speed 1m/s 10m/s Front Incline -0.177 -27.1755 Front Cover -0.619 -71.5122 Mid Cover -0.727 -86.8905 Rear Cover -0.449 -51.0341 Rear Incline -0.249 -29.474 91 Sample Data for Front Edge 1m/s Wind Speed 0 deg Angle of Attack Analysis: 1ms 0deg Length Units meter 0 x y z x-axis value (1) Velocity Magnitude (m/s) (2) Vx- Velocity (m/s) (3) Vy- Velocity (m/s) (4) Vz- Velocity (m/s) (5) Static Pressure (Pa) 1 -8.23 3.97 1.5 0 0.313 -0.305 -0.063 0.030 -0.077 2 -8.23 3.97 1.35 0.15 0.935 -0.875 -0.324 -0.001 -0.103 3 -8.23 3.97 1.2 0.3 0.398 -0.367 -0.137 -0.043 -0.108 4 -8.23 3.97 1.05 0.45 0.311 -0.288 -0.096 -0.064 -0.077 5 -8.23 3.97 0.9 0.6 0.243 -0.214 -0.086 -0.074 -0.070 6 -8.23 3.97 0.75 0.75 0.212 -0.171 -0.096 -0.079 -0.072 7 -8.23 3.97 0.6 0.9 0.214 -0.160 -0.115 -0.080 -0.078 8 -8.23 3.97 0.45 1.05 0.195 -0.135 -0.123 -0.063 -0.077 9 -8.23 3.97 0.3 1.2 0.180 -0.133 -0.106 -0.047 -0.076 10 -8.23 3.97 0.15 1.35 0.167 -0.146 -0.072 -0.034 -0.075 11 -8.23 3.97 0 1.5 0.148 -0.129 -0.065 -0.026 -0.073 12 -8.23 3.97 -0.15 1.65 0.129 -0.109 -0.064 -0.018 -0.072 13 -8.23 3.97 -0.3 1.8 0.146 -0.099 -0.100 0.012 -0.074 14 -8.23 3.97 -0.45 1.95 0.180 -0.122 -0.118 0.042 -0.078 15 -8.23 3.97 -0.6 2.1 0.236 -0.194 -0.109 0.074 -0.087 16 -8.23 3.97 -0.75 2.25 0.215 -0.184 -0.073 0.080 -0.079 17 -8.23 3.97 -0.9 2.4 0.209 -0.186 -0.056 0.075 -0.072 18 -8.23 3.97 -1.05 2.55 0.237 -0.217 -0.070 0.061 -0.071 19 -8.23 3.97 -1.2 2.7 0.274 -0.259 -0.070 0.040 -0.074 20 -8.23 3.97 -1.35 2.85 0.395 -0.382 -0.094 -0.013 -0.078 21 -8.23 3.97 -1.5 3 0.284 -0.275 -0.043 -0.058 -0.056 V avg 0.268 m/s Gap 0.625 in 0.016 m Width 118.000 in Short 118 2.997 m Long 572.5 A Area 0.048 m^2 Q = A * V Flow 0.013 m^3/s 92 C.2 Data for Model 2RcCG0.625 G28in S24in 2 Rail Cars 0.625 inch cover to cart gap 28 inch cart-to-cart gap 24 inch shutter Summary for Cart 2 Flow Rate (m^3/s) 0 degree Speed 1m/s 10m/s 100km/h Edge Front 0.004319 0.059339 0.153935 Left 0.018465 0.183372 0.487676 Right 0.016991 0.171173 0.492865 Rear 0.008179 0.103339 0.17168 Total 0.04795 0.51722 1.30616 Flow Rate (m^3/s) 45 degree Speed 1m/s 10m/s 100km/h Edge Front 0.002727 0.035743 0.136105 Left 0.043073 0.854221 1.848601 Right 0.036837 0.606529 1.162793 Rear 0.020053 0.229623 0.537432 Total 0.10269 1.72612 3.68493 Flow Rate (m^3/s) 90 degree Speed 1m/s 10m/s Edge Front 0.027985 0.136154 Left 0.070198 0.793109 Right 0.133515 1.020602 Rear 0.016077 0.155412 Total 0.24777 2.10528 93 Average Pressure (Pa) 0 degree Speed 1m/s 10m/s 100km/h Front Incline 0.02274 4.91 -112.39 Front Cover -0.062 -7.29 -145.21 Mid Cover -0.1137 -11.43 -159.5 Rear Cover -0.109 -10.923 -155.9 Rear Incline -0.15 -16.48 -171.87 Average Pressure (Pa) 45 degree Speed 1m/s 10m/s 100km/h Front Incline 0.0044 2.56 63.53 Front Cover -0.0188 -7.38 -50.46 Mid Cover 0.159 -15.8 -137.43 Rear Cover 0.183 15.7 124.35 Rear Incline 0.209 16.46 134.65 Average Pressure (Pa) 90 degree Speed 1m/s 10m/s Front Incline -0.357 -37.39 Front Cover -0.628 -77.88 Mid Cover -1.088 -126.3 Rear Cover -0.767 -83.65 Rear Incline -0.567 -56.1 94 C.3 Data for Model 2RcCG1 G28in 2 Rail Cars 1 inch cover to cart gap 28 inch cart-to-cart gap Summary for Cart 2 Flow Rate (m^3/s) 0 degree Speed 1m/s 10m/s 100km/h Edge Front 0.008439 0.074937 0.955518 Left 0.02946 0.255628 1.687553 Right 0.031794 0.275457 2.005666 Rear 0.014414 0.132477 0.890905 Total 0.08411 0.7385 5.53964 Flow Rate (m^3/s) 45 degree Speed 1m/s 10m/s 100km/h Edge Front 0.045727 0.470425 1.294983 Left 0.089546 1.024578 2.943513 Right 0.133283 1.274417 3.440301 Rear 0.019099 0.205873 0.545051 Total 0.28766 2.97529 8.22385 Flow Rate (m^3/s) 90 degree Speed 1m/s 10m/s Edge Front 0.030471 0.450013 Left 0.128562 1.151756 Right 0.163486 2.040411 Rear 0.027257 0.343105 Total 0.34978 3.98528 95 Average Pressure (Pa) 0 degree Speed 1m/s 10m/s 100km/h Front Incline -0.000227 -0.464 73.55 Front Cover -0.0324 -3.44 -21.34 Mid Cover -0.085 -8.47 -79.86 Rear Cover -0.086 -8.57 -86.1 Rear Incline -0.1216 -13.35 -130 Average Pressure (Pa) 45 degree Speed 1m/s 10m/s 100km/h Front Incline -0.0925 -5.84 23.1 Front Cover -0.495 -46.57 -156.36 Mid Cover -0.67 -61.80 -235.83 Rear Cover -0.307 -28.73 -33.04 Rear Incline -0.277 -24.46 -43.13 Average Pressure (Pa) 90 degree Speed 1m/s 10m/s Front Incline -0.387 -81.39 Front Cover -0.7586 -114.95 Mid Cover -0.89 -147.97 Rear Cover -0.737 -103.86 Rear Incline -0.552 -67.56 96 C.4 Data for Model 2RccG1 G28in S24in 2 Rail Cars 1 inch cover to cart gap 28 inch cart-to-cart gap 24 inch shutter Summary for Cart 2 Flow Rate (m^3/s) 0 degree Speed 1m/s 10m/s 100km/h Edge Front 0.010633 0.100406 0.120449 Left 0.038148 0.382212 0.799126 Right 0.035494 0.350816 0.76263 Rear 0.014721 0.139927 0.129423 Total 0.099 0.97336 1.81163 Flow Rate (m^3/s) 45 degree Speed 1m/s 10m/s 100km/h Edge Front 0.026965 0.265434 0.281596 Left 0.081988 0.837571 3.116627 Right 0.117067 1.143862 2.256671 Rear 0.011773 0.133718 0.822719 Total 0.23779 2.38059 6.47761 Flow Rate (m^3/s) 90 degree Speed 1m/s 10m/s Edge Front 0.029137 0.286116 Left 0.1756 1.711225 Right 0.171762 1.760427 Rear 0.030344 0.326875 Total 0.40684 4.08464 97 Average Pressure (Pa) 0 degree Speed 1m/s 10m/s 100km/h Front Incline 0.0345 3.32 -88.15 Front Cover -0.02 -1.996 -112.16 Mid Cover -0.0824 -8.41 -126.66 Rear Cover -0.083 -8.39 -124.122 Rear Incline -0.118 -12.96 -141.55 Average Pressure (Pa) 45 degree Speed 1m/s 10m/s 100km/h Front Incline -0.33 -29.52 -16.57 Front Cover -0.56 -51 -99.24 Mid Cover -0.77 -71.91 -201.70 Rear Cover -0.574 -52.2 43.4 Rear Incline -0.521 -47.66 58.04 Average Pressure (Pa) 90 degree Speed 1m/s 10m/s Front Incline -0.282 -28.9 Front Cover -0.668 -74.08 Mid Cover -1.104 -153.445 Rear Cover -0.55 -76.99 Rear Incline -0.386 -52.86 98 C.5 Data for Model 2RcCG1 G40in 2 Rail Cars 1inch cover to cart gap 40inch cart to cart gap Summary for Cart 2 Flow Rate (m^3/s) 0 degree Speed 1m/s 10m/s 100km/h Edge Front 0.009996 0.102592 0.16553 Left 0.067319 0.742965 1.167305 Right 0.06597 0.730681 1.224817 Rear 0.01229 0.130356 0.191611 Total 0.15557 1.70659 2.74926 Flow Rate (m^3/s) 45 degree Speed 1m/s 10m/s 100km/h Edge Front 0.031249 0.220538 0.997629 Left 0.063256 0.531445 3.333315 Right 0.109343 0.893781 3.138433 Rear 0.016954 0.107056 0.415793 Total 0.2208 1.75282 7.88517 Flow Rate (m^3/s) 90 degree Speed 1m/s 10m/s Edge Front 0.023564 0.228851 Left 0.210193 2.150656 Right 0.179832 1.751499 Rear 0.026637 0.272743 Total 0.44023 4.40375 99 Average Pressure (Pa) 0 degree Speed 1m/s 10m/s 100km/h Front Incline 0.0922 9.33 -116.87 Front Cover -0.0342 -3.73 -157.72 Mid Cover -0.107 -10.87 -161.49 Rear Cover -0.106 -10.7 -158.46 Rear Incline -0.1446 -15.2 -176.6 Average Pressure (Pa) 45 degree Speed 1m/s 10m/s 100km/h Front Incline -0.0036 4.2 93.22 Front Cover -0.626 -51.51 -264.865 Mid Cover -0.66 -54.55 -369.96 Rear Cover -0.381 -30.83 -113.4 Rear Incline -0.343 -27.26 -105.7 Average Pressure (Pa) 90 degree Speed 1m/s 10m/s Front Incline -0.159 -20.384 Front Cover -0.531 -60.7 Mid Cover -0.633 -71.67 Rear Cover -0.396 -45.263 Rear Incline -0.23177 -27.64 100 C.6 Data for Model Rc Open Rail Car Summary for RailCar Flow Rate (m^3/s) 0 degree Speed 1m/s 10m/s 100km/h Y-Dir 3.618487 31.98608 131.8098 Total 20.7017 204.6909 670.054 Flow Rate (m^3/s) 45 degree Speed 1m/s 10m/s 100km/h Y-Dir -2.08989 -14.0623 -60.4003 Total 15.44301 146.7581 456.5831 Flow Rate (m^3/s) 90 degree Speed 1m/s 10m/s Y-Dir -4.03352 -40.7779 Total 19.82322 202.3691 Cart Width 118 in 2.9972 m Cart Length 572.5 in 14.5415 m Total Area 43.5838 m^2 101 Average Speed (m/s) y-direction Angle of Attack 0 deg 45 deg 90 deg Sp ee d 1ms 0.083024 - 0.047951 - 0.092546 10ms 0.733899 -0.32265 -0.93562 100kmh 3.024286 - 1.385844 Average Speed (m/s) magnitude Angle of Attack 0 deg 45 deg 90 deg Sp ee d 1ms 0.474986 0.354329 0.45483 10ms 4.696491 3.367264 4.64322 100kmh 15.37393 10.47599 102 C.7 Data for Model RcCG0.5 Single Railcar Cover Gap 0.5in Summary for Cart Flow Rate (m^3/s) 0 degree Speed 1m/s 10m/s 100km/h Edge Front 0.067477 0.675607 2.343296 Left 0.042539 0.508949 1.739991 Right 0.035492 0.422048 1.467201 Rear 0.0041 0.038552 0.362733 Total 0.14961 1.64516 5.91322 Flow Rate (m^3/s) 45 degree Speed 1m/s 10m/s 100km/h Edge Front 0.033495 0.273766 1.472825 Left 0.030005 0.320249 1.271451 Right 0.03172 0.364284 1.281571 Rear 0.001074 0.027546 0.181324 Total 0.09629 0.98584 4.20717 Flow Rate (m^3/s) 90 degree Speed 1m/s 10m/s Edge Front 0.029203 0.199515 Left 0.042539 1.032977 Right 0.035492 0.960361 Rear 0.0041 0.046682 Total 0.11133 2.23953 103 C.8 Data for Model RcCG0.625 Single Railcar 0.625in Cover Gap Summary for Cart 1 Flow Rate (m^3/s) 0 degree Speed 1m/s 10m/s 100km/h Edge Front 0.109978 1.142 2.940208 Left 0.055347 0.561826 2.669256 Right 0.068223 0.702212 2.980628 Rear 0.010456 0.129218 0.362262 Total 0.244 2.53526 8.95235 Flow Rate (m^3/s) 45 degree Speed 1m/s 10m/s 100km/h Edge Rear 0.01232 0.088592 0.496953 Right 0.083059 0.674626 2.478088 Left 0.054345 0.38342 1.449253 Front 0.058599 0.532866 1.547219 Total 0.20832 1.6795 5.97151 Flow Rate (m^3/s) 90 degree Speed 1m/s 10m/s Edge Rear 0.017035 0.191578 Right 0.098505 0.865469 Left 0.119097 1.16014 Front 0.017286 0.177852 Total 0.25192 2.39504 104 C.9 Data for Model RcCG0.625 Single Railcar 1in Cover Gap Summary for Cart Flow Rate (m^3/s) 0 degree Speed 1m/s 10m/s 100km/h Edge Front 0.131238 1.126087 4.482862 Left 0.124591 1.113989 4.674496 Right 0.118632 1.122311 4.181418 Rear 0.016043 0.14818 0.797009 Total 0.39051 3.51057 14.1358 Flow Rate (m^3/s) 45 degree Speed 1m/s 10m/s 100km/h Edge Rear 0.017838 0.128356 0.399502 Right 0.092438 0.926454 3.485164 Left 0.058125 0.573909 2.552083 Front 0.06391 0.489298 2.599367 Total 0.23231 2.11802 9.03612 Flow Rate (m^3/s) 90 degree Speed 1m/s 10m/s Edge Rear 0.033934 0.452695 Right 0.200403 2.537982 Left 0.198059 1.722651 Front 0.022199 0.354713 Total 0.45459 5.06804 105 C.10 Peak Cover Pressures Peak Cover Pressures Cover Pressures (Pa) - 1m/s windspeed 2RcCG0.625 G28in 2RcCG0.625 G28in S24in 2RcCG1 G28in 2RcCG1 G28in S24in 2RcCG1 G40in Inclines 0.337 0.567 0.552 0.521 0.343 Top 0.727 1.088 0.890 1.104 0.662 Cover Pressures (Pa) - 10m/s windspeed 2RcCG0.625 G28in 2RcCG0.625 G28in S24in 2RcCG1 G28in 2RcCG1 G28in S24in 2RcCG1 G40in Inclines 33.001 56.100 81.390 52.860 27.640 Top 86.891 126.300 147.970 153.445 71.670 Cover Pressures (Pa) - 100km/h windspeed 2RcCG0.625 G28in 2RcCG0.625 G28in S24in 2RcCG1 G28in 2RcCG1 G28in S24in 2RcCG1 G240in Inclines 150.445 171.870 130.000 141.550 189.360 Top 136.955 159.500 235.830 201.700 396.300 106 C.11 Cover Pressure Comparisons for Double Railcar Models Pressure Top Inclines 0.625in Gap No Shutter 24in Shutter No Shutter 24in Shutter 1m/s 66.82% 100.00% 59.50% 100.00% 10m/s 68.80% 100.00% 58.83% 100.00% 100km/h 85.87% 100.00% 87.53% 100.00% Pressure Top Inclines 1in Gap No Shutter 24in Shutter No Shutter 24in Shutter 1m/s 80.62% 100.00% 100.00% 94.38% 10m/s 96.43% 100.00% 100.00% 64.95% 100km/h 100.00% 85.53% 91.84% 100.00% Pressure Top Inclines 1in Gap 28in Gap 40in Gap 28in Gap 40in Gap 1m/s 100.00% 74.38% 100.00% 62.14% 10m/s 100.00% 48.44% 100.00% 33.96% 100km/h 59.51% 100.00% 68.65% 100.00% 107 C.12 Flow Rate Comparisons for Double Railcar Models Flow Rates 2RcCG0.625 G28in 2RcCG0.625 G28in S24in 0 deg 1m/s 100.00% 59.11% 45 deg 1m/s 100.00% 56.94% 90 deg 1m/s 100.00% 89.03% 0 deg 10m/s 100.00% 62.37% 45 deg 10m/s 100.00% 79.84% 90 deg 10m/s 100.00% 66.80% 0 deg 100km/h 81.83% 100.00% 45 deg 100km/h 100.00% 64.20% 2RcCG1 G28in 2RcCG1 G28in S24in 0 deg 1m/s 84.96% 100.00% 45 deg 1m/s 100.00% 82.67% 90 deg 1m/s 85.97% 100.00% 0 deg 10m/s 75.87% 100.00% 45 deg 10m/s 100.00% 80.01% 90 deg 10m/s 97.57% 100.00% 0 deg 100km/h 100.00% 32.70% 45 deg 100km/h 100.00% 78.77% 2RcCG1 G28in 2RcCG1 G40in 0 deg 1m/s 54.06% 100.00% 45 deg 1m/s 100.00% 76.76% 90 deg 1m/s 79.45% 100.00% 0 deg 10m/s 43.27% 100.00% 45 deg 10m/s 100.00% 58.91% 90 deg 10m/s 90.50% 100.00% 0 deg 100km/h 100.00% 49.63% 45 deg 100km/h 100.00% 95.88% "@en ; edm:hasType "Thesis/Dissertation"@en ; vivo:dateIssued "2012-11"@en ; edm:isShownAt "10.14288/1.0071822"@en ; dcterms:language "eng"@en ; ns0:degreeDiscipline "Civil Engineering"@en ; edm:provider "Vancouver : University of British Columbia Library"@en ; dcterms:publisher "University of British Columbia"@en ; dcterms:rights "Attribution 3.0 Unported"@en ; ns0:rightsURI "http://creativecommons.org/licenses/by/3.0/"@en ; ns0:scholarLevel "Graduate"@en ; dcterms:title "Developing performance based design guidelines for the railcar cover system"@en ; dcterms:type "Text"@en ; ns0:identifierURI "http://hdl.handle.net/2429/43514"@en .