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Drag reduction of cube-van through boundary-layer control: wind tunnel experiments and prototype road… St Hill, Simon 1993

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DRAG REDUCTION OF CUBE-VAN THROUGH BOUNDARY-LAYER CONTROL : WIND TUNNEL EXPERIMENTS AND PROTOTYPE ROAD TESTS. by Simon St Hill B. Eng, Royal Melbourne Institute of Technology, 1988 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in THE FACULTY OF GRADUATE STUDIES Department of Mechanical Engineering We accept this thesis as conforming to the required standard  THE UNIVERSITY OF BRITISH COLUMBIA December, 1992 © Simon St Hill  In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission.  (Signature)  Department of  /i / (1.171-A)/Cf)g ,  ---  -  The University of British Columbia Vancouver, Canada  Date ^—^  DE-6 (2/88)  -  1992-  ^,/k)  11  ABSTRACT Due to increasing fuel cost and emphasis on energy conservation as well as pollution control, there has been considerable interest in improving propulsive efficiency of road vehicles. Reduction in aerodynamic resistance is one aspect of it. Although aerodynamically contoured automobiles has become a standard design practice. Trucks have changed little over the past three decades. The thesis presents results of an organised and extensive wind tunnel test-program, complemented by full-scale road tests, aimed at assessing the effectiveness of two boundary-layer control procedures for reduction of the pressure drag of a cube-van. Wind tunnel results, obtained using 1/6th scale models, at a subcritical Reynolds number of 10 5 , suggest that both the Moving Surface Boundary-layer Control (MSBC) as well as the tripping of the boundary-layer using fences reduce the pressure drag coefficient. Although both the concepts are promising, application of the entirely passive fence procedure appears more attractive from an economic consideration as well as the ease of implementation. The road tests with a full-size cube-van substantiated the trends indicated by the fence data although the actual drag reduction observed was lower (yet quite significant, = 16.6%) than that predicted by the wind tunnel tests. This may be attributed to a wide variety of factors including the differences in the geometry (models; fences and their orientation), operating conditions (Reynolds number; yaw; wind variations in magnitude and direction; turbulence; road boundary-layer; road surface condition), and measurement errors. However, the objective of the study was to assess potential of the concepts which, indeed, is quite promising.  111  Fuel consumption results also substantiated the drag reduction trend. As expected they depend on the gearing condition and hence no general expression applicable to all speed ranges is available. As anticipated the data show a rapid increase in the fuel consumption efficiency at the top end of the speed range. It is concluded that fences can lead to a significant improvement in drag reduction and fuel consumption when applied to flat-faced trucks if positioned correctly. They represent a more elegant, versatile, and cheaper alternative to the 'nose cones' and deflectors available in the market. It is recommended that further road tests should be conducted using both boundary-layer control devices.  iv  TABLE OF CONTENTS ABSTRACT^  ii  TABLE OF CONTENTS^  iv  LIST OF FIGURES^  vi  LIST OF TABLES NOMENCLATURE^  xi  ACKNOWLEDGEMENT^  xii  1^INTRODUCTION^  1  1.1 Background^  1  1.2 Theory of Fences^  2  1.3 A Brief Review of the Relevant Literature ^4 1.4 Scope of the Present Investigation ^ 2 TEST PROCEDURE^ 2.1 Wind Tunnel Test Procedure^  14 17 17  2.1.1 Model specifications^  17  2.1.2 Wind tunnel^  18  2.1.3 Model support system and instrumentation^18 2.2 Full Scale Test Procedures^  22  2.2.1 Truck specifications ^  22  2.2.2 Torque and speed measurements ^30 2.2.3 Fuel flow measurement^  33  2.2.4 On-road test procedure ^  34  3^RESULTS AND DISCUSSION ^  45  3.1 Wind Tunnel Model tests^  45  3.1.1 Wind tunnel models with fences^ 45 3.1.2 Wind tunnel model with a rotating cylinder and fences 51 3.2 Full Scale Tests^  56  3.3 Comparison Between Model and Full Scale Test^64 4 CONCLUDING REMARKS^ 4.1 Summary of Results^  69 69  4.1.1 Wind tunnel model tests^  69  4.1.2 Full scale tests^  70  4.2 Recommendation for future study^  71  REFERENCES^  73  APPENDIX A : PROGRAM LISTINGS ^  78  APPENDIX B : FORCE REGRESSION PLOTS ^  88  APPENDIX C : FUEL CONSUMPTION PLOTS^ 113  vi  LIST OF FIGURES Figure  1-1 A schematic diagram showing the effect of fences on the front face of a bluff body, on pressure distribution: (a) without fences; (b) with feces  3  1-2 The practical application of moving wall for boundary layer control. 10 1-3 Schematic diagrams explaining principles of the MSBC and the boundary layer trip devices in reducing drag on bluff bodies ^13 2-1 Photograph of the 1/6 scale cube-van model ^  17  2-2 University of British Columbia boundary-layer wind tunnel ^19 2-3 Model Arrangement in the Wind Tunnel ^  21  2-4 The truck as tested with an increased frontal area. This was achieved by enlarging the box through raising the roof. The extension was in a removable modular form. This is referred to as the 'extended roof case. 23 2-5 The extended roof truck with a horizontal fence. ^24 2-6 The Truck with the extended roof, and all fences  ^  25  2-7 A block diagram of the test set up. ^  28  2-8 An example of the computer display. ^  29  vii 2-9 Equipment layout in the truck. ^  30  2-10 Torquemeter as installed in the truck. ^  31  2-11 Force calibration method  ^  32  2-12 Photograph of the fuel meter installed on the truck. ^34 2-13 Test route map (n.t.s.). ^  39  3-1 Wind tunnel test results for the cube-van model (1/6 scale) to determine optimum locations of vertical fences 1 and 2. ^46 3-2 Wind tunnel test results for the cube-van model to determine optimum location of horizontal fence 3. ^  47  3-3 Wind tunnel test results for the cube-van model with one horizontal and tow vertical fences. Note the horizontal fence extends to the entire width of the van. 48 3-4 Wind tunnel test results for the cube-van model with two horizontal and two vertical fences.^  49  3-5 Wind tunnel test results for the cube-van model showing optimum four fence configuration.^  50  3-6 Effect of momentum injection and kit position on the drag reduction of the cube-van model.^  52  3-7 Effect of the height and spacing of the two vertical fences on the drag of the cube-van model. Note, the kit is in its optimum orientation, however, the cylinder is not rotating. Of course, the rounded upper leading edge presented by the cylinder 54  viii  3-8 Effect of the cylinder rotation on the drag of the cube-van in the hybrid MSBC/fence configuration.^  55  3-9 Comparative force regression analysis showing the effect of fences. 61 3-9b Comparative force regression analysis showing the effect of fences in terms of CD.^  62  3-10 Reduction in fuel consumption due to the presence of fences as affected by the speed.^  63  3-11 Wind tunnel test results for the cube-van model with rounded corners and vertical fences.^  67  3-12 Wind tunnel test results for the cube-van model with rounded corners, vertical, and horizontal fences. ^  68  B-1 Regression analysis of the force data for the modified truck with extended roof (baseline or reference case).^  89  B-3 Analysis of the force data obtained with one horizontal and two vertical fences installed on the cube-truck during the road tests Test Numbers 1-4.^  109  C-1 Fuel consumption data for the reference (baseline) configuration Test Numbers 1-12.^  114  C-2 Fuel consumption data with horizontal fence Test Numbers 1-8.^  126  ix  C-3 Fuel consumption as affected by the truck speed in the presence of one horizontal and two vertical fences Test Numbers 1-4.^  134  x  LIST OF TABLES Table  2-1 Geometry of horizontal and vertical fences used during the roadtests.^  26  2-2 Details of the road tests conducted with the full-scale truck configurations.^ 3-1 Results based on the road test data^  37 59  xi  NOMENCLATURE  A^frontal projected area, m 2 CD^coefficient of drag, D / (1/2) p U 2 A d^hydraulic diameter, (4.100 1/2 , m F^force exerted by the wheels to propel the truck, N Hf fence height, m Hk height of MSBC kit above the truck box, m  p.^standard air viscosity, 17.8 x 10 -6 , kg/ms P^barometric pressure, kPa Pf^pressure on the front face of a body, Pa  Pr^pressure on the rear face of a body, Pa p^air density, kg/m 3  Rn Reynolds number, pUd/pt T^absolute temperature, °K U^free stream velocity, m/s U,^surface velocity of the cylinder, m/s x f^horizontal coordinate of the vertical fence, m yf^vertical coordinate of the horizontal fence, m  xii  ACKNOWLEDGEMENT Special thanks is extended to my supervisor, Dr V.J. Modi for his time and guidance throughout this project. His insight and amiable nature has made this project a thoroughly enjoyable experience. The assistance of Oliver B. Ying, M.A.Sc Graduate and Mr Jimmy Ng, Project Engineer in the installation of instrumentation, and advice are gratefully acknowledged. The investigation reported here was supported by the Science Council of British Columbia, Grant Nos. AGAR 5-53628, 5-53698, Natural Sciences and Engineering Research Council of Canada, Grant No. A-2181, and C.P. Express Transport Ltd.  1  1^INTRODUCTION 1.1 Background With the dwindling fossil fuel reserves, and our ever increasing dependence on them, it is no longer sufficient to have a machine or device that simply 'works', it must work at its optimum efficiency. As fossil fuel reserves dry up, the cost in obtaining them will increase, and hence it rightly makes economic sense to improve efficiency to as high a level as possible. Of course, the economist will also asses the cost involved in making the device more efficient, which, in fact this must be taken in to consideration in any engineering research. The proposed project deals with one such situation, that of minimization of the aerodynamic drag of trucks. The truck transportation industry is currently very large in Canada, and is continuing to grow. Presently two thirds of all goods in North America are transported by trucks, and the average truck travels approximately 130,000 - 150,000 km per year. At highway speeds (80 100 kph) approximately 50 % of the power is used to overcome aerodynamic drag. With this in mind several researchers and truck manufacturers have produced various fairings with moderate success. Existing fairings have achieved good reductions in fuel consumption. An example of this is the "Nose Cone". Its manufacturers claim a reduction in fuel consumption of 5% under ideal circumstances [1]. The "Nose Cone" fairing costs up to $555, excluding the installation charge. Similar types of devices, such as the "Air Shield", make claims of the same order of saving, but are more expensive.  2  Ying [2] indicated that fences could effectively reduce aerodynamic drag on trucks by 23 %. These devices are passive, simple to manufacture, and install, and seem are quite promising. The drag reduction correlates with a fuel consumption reduction of approximately 17% at a speed of 100 kph. This is a marked improvement from the claimed results of "Nose Cone", and hence warrants further investigation. Thus encouraging results of Ying on fences as drag reducing elements forms the basis of the present study. A specific model of a cube-van was tested in the wind tunnel to arrive at an optimum configuration of the fences. The corresponding prototype was road tested to determine the actual drag reduction and fuel saving realized.  1.2 Theory of Fences The operating principle of fences is rather elegantly simple. The objective is to trip the boundary-layer and thus interfere with the pressure recovery. The resulting pressure is lower. Fences, when carefully placed on the front face of a bluff body would thus lead to a reduction in drag. The principal is illustrated in Figure 1-1  Di = jj P i dx dy D a > Db Figure 1-1  A schematic diagram showing the effect of fences on the front face of a bluff body, on pressure distribution: (a) Without fences; (b) with fences.  4  As can be seen from the above figure the effective frontal area has been reduced, the pressure distribution over the front of the body has also been reduced, and hence there is a significant reduction in the drag of the body.  1.3 A Brief Review of the Relevant Literature A comprehensive literature review of road vehicle aerodynamics suggest that although the aerodynamically contoured car design has become a standard practice lately, trucks and buses have changed little during the past 30 years [3-6]. Most of the modifications have been limited to rounded edges with provision for vanes, skirts, and flow deflectors. The benefit due to some of the "add-on" devices is still a matter of controversy and, at best, marginal under conditions other than the specific ones used in their designs. Bearman [7] has presented an excellent review of the subject (with 54 references cited). The thesis by Wacker [8] also discusses the limited influence of the "add-on" devices with a possibility of increasing the drag under non-optimal conditions. On the other hand, it was found that judicious choice of ground clearance, gap size between the tractor and the trailer, and back inclination can reduce the drag coefficient by a significant amount. The comprehensive investigation, aimed at assessing the effect of the boundary-layer modification on truck aerodynamics, is presented by Ying [2]. He investigated both the influence of judiciously placed fences as well as the rating elements for Moving Surface Boundary-layer Control (MSBC). His findings have led to the present investigation where a model of a smaller cube-truck was tested with the boundary-layer control achieved through both the procedures. The model study was  5  complemented by extensive road tests with the more attractive, passive, fence concept. A word concerning model and full scale testing of trucks would be appropriate. Aerodynamic testing of trucks began in the mid 1970's. Model tests were initially conducted with deflector type devices, and involved simple modifications to existing vehicles. A wide range of devices were tested, with an equally scattered range of results, fortunately they were mostly positive. This led to the installation of deflectors to large tractor trailer units, on long distance hauls. As testing of the devices and resulting modifications progressed, the measured drag reduction continued to grow. However, as late as 1987, fleet management companies were not noting significant reduction in their fuel consumption [9]. This sparked interest in full scale testing of the trucks, in an attempt to  see why the results did not translate. Buckley [10] developed a new test method, and suggested it as an  improvement of the standard S.A.E. J1321 procedure. The approach involves two trucks, and a chase car. This method seems to be quite accurate, however it is costly. Saunders et. al. [11] used the method in Australia, where he found the correlation between the wind tunnel and prototype results to be quite poor. In an attempt to determine the cause of discrepancy, his graduate student, Simon Watkins, started a series of tests, which mainly concentrated on the local turbulence levels. The results [12] suggest that the wind tunnel studies, in smooth laminar flow conditions (turbulence level < 0.1 %), tend to give more favourable drag reduction results. A turbulence level of 3-4 %, which would increase with yaw, should be more representative of the road conditions. When this paper was published the author was completing his undergraduate degree  6  at the Royal Melbourne Institute of Technology, and his final year project, under Watkins, was concerned with the effects of longitudinal turbulence intensity on saloon cars. His findings indicated that a 15% variation in the measured drag can be attributed to the turbulence which turned out to be of the same order as the maximum expected gain due to the devices. Full scale aerodynamic testing of vehicles is an established practice. Many automobile manufacturers conduct extensive tests of their vehicles at the full scale level. General Motors has carried out systematic experiments to ensure that the full scale tests are compatible with the wind tunnel results [13]. Generally these tests involve "coastdown" which is relatively accurate, however, significant modifications had to be introduced to the procedure in order to achieve close correlation between the wind tunnel data and the prototype road results. This modification mostly involved attending to the simplifying assumptions made in conducting the road-test. Their analysis also concluded that there was no variation of error with C D .A. Although the largest value of the (C D .A) they tested was 1.69 m 2 , whereas in this report it was greater than 3.0 m 2 . Other coastdown methods take into account yaw angle, and grade with carefully surveyed test-tracks. Remenda et al. [14] conducted a series of experiments using a very small vehicle in order to prove that they could determine the drag coefficient for a worst case scenario. Since the forces on their vehicle were relatively small their accurate measurement was difficult. The reported results are quite good, however, they do require an extensive survey of the test-track prior to starting. Although most of the reported full-scale tests involve the coastdown method, there is another approach of equal value based on the steady  7  state torque method. In this, which is mostly used in Europe, the vehicle is instrumented with torquemeters, and its speed and applied torque are monitored. This alternative approach to coastdown method is believed to be just as accurate. Passmore et al. [15] conducted a comparison of the two methods. They concluded that for a similar amount of data the coastdown method provided a slightly more accurate means of determining the drag. It should be noted, however, that it is easier to obtain significantly more data with the steady state torque method than with the coast down approach. Passmore et al. took 20 seconds of data, at 4 Hz for each speed, which amounts to 80 points for each speed. Tests were conducted at 12 speeds making a data pool of 960 points. In the present study a sample rate of 1 Hz was used as no additional information or accuracy can be obtained by employing a higher sampling rate. This slowing of the sampling rate, whilst increasing the number of data points approximately 6 fold would extend the data acquisition period by a factor of 23. By extending the test the variable conditions have more time to average out, and hence increase the general accuracy. Test results have also been reported have been conducted which give a 'rule of thumb' as to the amount of power required to overcome various drag forces resisting the vehicle motion, and the importance of yaw angle analysis. Drollinger [16] found that at 58 mph (94 kph) the aerodynamic drag is equal to the rolling resistance. It was also reported that there is only a 10% probability of yaw the angle being grater than 40, and only a 3% probability of yaw the angle being greater than 100. Hence, yaw angle measurement was not considered vital. Earlier Inagawa [17] also found that aerodynamic drag was equivalent to rolling drag at approximately 100 kph. A small discrepancy in the predicted speed may be attributed to  8  differences in the shape of the trucks. He went further and stated that the rolling resistance was approximately 1% of the truck weight (loaded or unloaded) with the recommended tyre pressure. In the present study, this would amount to a total Coulomb friction force of around 400 N. Ever since the introduction of the boundary-layer concept by Prandtl, there has been a constant challenge faced by scientists and engineers to minimize its adverse effects and control it to advantage. Methods such as section, blowing, vortex generators, turbulence promoters, etc. have been investigated at length and employed in practice with a varying degree of success. The vast body of literature accumulated over years has been reviewed rather effectively by several authors including Goldstein [18], Lachmann [19], Rosenhead [20], Schlichting [21], Chang [22], and others. However, judicious tripping of the flow on large bodies using fences has received relatively less attention. Irrespective of the method used the main objective of a control procedure is to prevent, or at least delay, separation of the boundary layer. A moving surface attempts to accomplish this in two ways : (i)  it retards growth of the boundary layer by minimizing relative motion between the surface and the free stream;  (ii)  it injects momentum into the existing boundary layer.  A practical application of the moving wall for boundary layer control was demonstrated by Favre [23]. Using an airfoil with the upper surface formed by a belt moving over two rollers (Figure 1-2), he was able to delay separation until the angle of attack reached 55 0 where the maximum lift coefficient CL max = 3.5 was realised. Alvarex-Calderon and Arnold [24]  9  carried out test on a rotating cylinder flap to develop a high lift airfoil for STOL type aircraft. The system was tested in flight on a single engine high-wing research aircraft, and appeared quite promising. Of some interest is the North American Rockwell designed OV-10A aircraft with was flight tested by NASA's Ames Research Center (Cichy et al. [25], Weiberg et al. [26], and Cook et al. [27]). Cylinders located at the leading edges of the flaps were rotated at high speeds with the flaps in the lowered position. The main objective of that test-program was to assess the handling qualities of the propeller powered STOL type aircraft at higher lift coefficients. The aircraft was flown at speeds of 29 - 31 m /s, along approaches up to - 8°, which correspond to a lift coefficient C L =4.3. In the pilot's opinion any further reductions in approach speed were limited by the lateral directional stability and control characteristics.  Figure 1-2 The practical application of moving wall for boundary layer control.  I-4  0  11  In terms of trying to understand the phenomenon at the fundamental level Tennant's contribution to the field is significant. Tennant et al. [28] have conducted tests with a wedge shaped flap having a rotating cylinder as the leading edge. Flap deflection was limited to 15° and the critical cylinder velocity necessary to suppress separation was determined. The effect of increasing the gap-size (between the cylinder and the flap surface) was also assessed. No effort was made to observe the influence of an increase in the ratio of cylinder surface speed (U) to the free stream velocity (U) beyond 1.2. Through a comprehensive wind tunnel test-program involving a family of airfoils with one or more cylinders forming moving surfaces, complemented by the surface singularity numerical approach and flow visualisation, earlier studies by Modi et al.[30-33] have shown spectacular effectiveness of the concept, which increased the maximum lift coefficient by move than 200 % and delayed stall angle to 48°. Yet another approach to boundary-layer control can be through its tripping by judiciously located fences on the front face of a bluff body. This interferes with the pressure recovery thus promising to reduce drag. The basic concepts involved in the boundary-layer control through the above two methods are illustrated in Figure 1-3. It shows a bluff body, a tow dimensional prism, located in a fluid stream at zero angle of attack. Pf and P b are pressures on the front and rear faces, respectively. They are  assumed to be uniform over the faces, in this illustrative example, for simplicity. Obviously by increasing P b and /or decreasing Pf we can reduce the pressure drag. MSBC tries to increase P b by keeping the flow attached. On the other hand, fences reduce Pf by tripping the boundary-  12  layer. These principles are explained through diagrams of flow past a circular cylinder in the same figure. At the stagnation point the pressure is the largest and the pressure coefficient is 1. The boundary-layer separates at e s forming the wake. In the wake, the pressure is essentially uniform at a lower value. This is what fences try to achieve. If the separation is prevented, ideally the pressure will reach the stagnation value. This is what the MSBC tries to accomplish.  It is apperent that by increasing Pb or reducing Pf we can reduce the pressure drag. * MSBC tends to increase Pb by keeping the flow attached * Fences tend to reduce Pf by tripping the boundary-layer and preventing the pressure recovery. Potential Flow •  Figure 1-3 Schematic diagrams explaining principles of the MSBC and  the boundary layer trip devices in reducing drag on bluff bodies  14  1.4 Scope of the Present Investigation The present study builds on this background and assesses the effectiveness of the above mentioned two boundary-layer control procedures in reducing drag of a cube-van. The carefully planned project has two phases: (a)^Wind tunnel tests using 1/6 scale model of a cube-van with: (i)  the MSBC applied at the top front edge of the van;  (ii)  the trip fences mounted on the front face of the van  (b)^full scale prototype road tests using the passive fence with promised to be quite effective, easy to install and maintain, as well as economical. It would be appropriate to point out that eventual application of fences is intended for semi-trailers, i.e. tractor-trailer truck configurations. Long distance journeys at a relatively high but essentially uniform speed would make such configurations ideal candidates for aerodynamic drag reduction. However, at this stage of the development the focus is not on the acquisition of precise data but on the validity of the concept and gaining some appreciation as to the extent of benefit that can be realized. A relatively inexpensive cube-van, with appropriate instrumentation and well throughout test methodology as well as data reduction procedure can provide the necessary information. Hence commitment to a high cost associated with acquisition, operation and maintenance of semi-trailer was considered unwarranted at this stage of development.  15  However, factors associated with implementation of the MSBC (accomplished through a kit, comprising of a bearing mounted powered cylinder, that can be bolted to the front face of the van) were thoroughly explored. At the outset, it was recognized that installation of fences would be quite simple, on the other hand implementation of the MSBC device would require careful planning. Construction of a 600 mm diameter, light but sufficiently strong cylinder, supported by a pair of self aligning bearings, rotating at around 5000 rpm and dynamically balanced, does present a challenge. In fact, local inquiries, including the BCIT Machine Shop (perhaps the best in B.C.) suggested that no such facility was available in greater Vancouver. Furthermore, although there were several options as to the drive system for the cylinder rotation, they all would require careful study. For example, power required by an electric motor, though small compared to the truck power, was far in excess of the current electrical system rating. Hence installation of a larger alternator would be required. One option would be to power the cylinder hydraulically. A pump driven by the truck engine may power the hydraulic motor. However, this would entail additional equipment and installation cost of a significant amount. A possibility of compressed airmotor drive system was also explored to gain some appreciation as to the relative merit and problems involved.  The scope of the investigation and various phases involved may be summarized as follows:  16  a)  Model tests in the wind tunnel using both MSBC and fence type devices. Acquisition of the measuring instrumentation and their installation.  b)  Development of a test methodology that would accurately determine aerodynamic drag as well as rolling resistance, and internal viscous losses.  c)  Establish a methodology for data processing, to get reliable, repeatable, and accurate results. Development of the software necessary for interrogation of instrumentation in an on-road environment, as well as all post processing of data.  d)  Road tests with several configurations of a cube-van to assess performance of fences as a drag reducing device. Configurations of a GMC van tested were: i)  standard box, as supplied by Grumman Olsen Ltd;  ii)  standard box, with sharp corners and raised roof;  iii)  same as ii) with horizontal fence added;  iv)  same as iii) with two vertical fences added.  The fence locations were determined from wind tunnel tests. It may be pointed out that the cube-van model used in the wind tunnel tests, though similar, differed significantly in detail from the prototype. Furthermore , the model was based on a older version which had a much larger hood.  17  2 TEST PROCEDUR.E 2.1 Wind Tunnel Test Procedure 2.1.1 Model specifications  A 1/6 scale cube truck model was constructed using Plexiglass. The model is based on a mid 1980's GMC truck, with van body mounted on it. It has a hydraulic diameter of 469.2 mm, and can be used to assess effectiveness of both the MSBC device and the boundary-layer trip fences, or combinations of the two.  Figure 2-1 Photograph of the 1/6 scale cube-van model  18  2.1.2 Wind tunnel The truck model was tested in the boundary-layer wind tunnel at the University of British Columbia (Figure 2-2). The tunnel is an open circuit type powered by an 80 kW three phase motor, which drives an axial flow fan at a constant 700 rpm. The tunnel wind speed is varied using a pneumatic controller to alter either the rotating frequency of the fan or the blade pitch. The settling section contains a honeycomb and four screens to smooth the flow as it enters a 4.7:1 contraction section. The tunnel has a test-section of 2.44 m width by 1.6 m height, and in 24.4 m length, consisting of eight 3.05 m long bays with a variable height roof to allow for boundary-layer correction. The stable wind speed of the tunnel is in the range of 2.5 to 25 mis. The adjustable test-section roof was set for zero pressure gradient. The present set of experiments were carried out in the second bay which provided smooth flow with a turbulence level less than 0.4 %. The typical test Reynolds number based on the hydraulic diameter was 2 x 10 5 .  2.1.3 Model support system and instrumentation The truck model was supported by four steel guy wires which were suspended from the ceiling and carried turnbuckles to help level the model. As the length of the wire (1450 mm) is much larger than the maximum horizontal displacement of the truck model (< 50 mm) the drag induced displacement was essentially linear in the downstream direction.  Figure 2-2 University of British Columbia boundary-layer wind tunnel  20  Variation in the drag due to the fences was relatively small, and required the use of a sensitive transducer for its measurements. The model was suspended from the ceiling by four wires, as described previously, to minimise the effect of friction. The drag induced downstream motion of the model was transmitted via an inelastic cable to a cantilever beam with a pair of strain gages near its root. The gages formed a part of the Wheatstone Bridge (of the Bridge Amplifier Meter, BAM) and the amplified, filtered output was recorded using a DISA Voltmeter. The sensitivity of the drag measurements was approximately 4 N/ V. The calibration of the cantilever using static loads was performed twice during a test-session, before and after the tests; and the average calibration value was adopted to account for any drift. Figure 2-3 shows schematically the model support and drag measurement system.  Figure 2-3 Model Arrangement in the Wind Tunnel  22  2.2 Full Scale Test Procedures 2.2.1 Truck specifications  The truck tested was a 1991, Chevy, one tonne Cube Van. This type of vehicle is generally used for small deliveries, and transport around town. Our test used this vehicle at a wide range of speeds. The vehicles specification appears below: •  Model  G30 Commercial Cut-away, 146" WB, 2WD  •  Body And Trim  Standard Model  •  Package Code  Level 1  •  GVWR  4536 Kg  •  Engine  5.7 litre V8  •  Transmission  4 Speed Automatic  •  Mirrors  Camper Type, Painted  •  Final Drive  4.1:1  •  Tyre Sizes  LT225/75R - 16/D  •  Tyre Pressure  290 kPa  •  Box Height  2.150 m / 2.740 m  •  Box Width  2.420 m  •  Frontal Area  6.016 m 2 / 7.444 m 2  •  Hydraulic Dia.  2.768 m / 3.908 m  •  Reynolds No.  5 x 10 5 To 8 x 10 6  23  A photograph of the truck with its additional height is presented in Figure 2-4. As can be seen the removable top section is in the plain aluminium colour, thus illustrating its relative size.  Figure 2-4 The truck as tested with an increased frontal area. This was achieved by enlarging the box through raising the roof. The extension was in a removable modular form. This is referred to as the 'extended roof case.  2.2.2 Test configurations and instrumentation Four different configurations of the truck were used during the roadtests: the plain cube van as purchased; the one with the extended roof added; the extended roof truck with a horizontal fence, and finally the one with one horizontal and two vertical fences installed at their optimum  24  locations as determined by Ying [2]. The extended roof configuration served as the baseline reference. Each of the configurations was subjected to extensive road tests to ensure repeatability and accuracy of data. Figure 2-5 and 2-6 show the extended box configuration with a horizontal fence, and horizontal-vertical combination respectively. The heights and locations of the fences appear in Table 2-1.  Figure 2-5 The extended roof truck with a horizontal fence.  25  Figure 2-6 The Truck with the extended roof, and all fences  26  Table 2-1 Geometry of horizontal and vertical fences used during the road-tests. Fence  Vertical Location Yf /d (Yf)  Horizontal 1125 mm 0 288  Horizontal Location Xf Id (Xf) -  -  Size length Full width  height  thickness  152/0.039*  1/0.00026 *  152/0.039*  1/0.00026*  2240 mm Vertical  -  -  968 mm  0.333 1420 mm From top  Note : The box dimensions were 2.740 x 2.240 m (height x width) Hydraulic diameter, d, equals 3.908 m. * Nondimentionalized with respect to d.  The instrumentation consisted of two transducers: a torquemeter, and a fuel meter. They were connected to a Dycor DA \M 100 analog to digital converter, which in turn was interfaced with a 386 SX lap top computer. Figure 2-7 shows a block diagram indicating the general set-up of the equipment on the truck. The computer logged data from each transducer, sampled at a rate of 1 Hz, and displayed it in real time. The on-screen output was designed to display the drive train force versus vehicle speed, an example of which can be seen in Figure 2-8. The steady state torque method permits an accurate determination of the drag coefficient, its variation as a function of speed. This results in the precise estimate of drag reduction, effectively incorporating the yaw angle sensitivity and Reynolds number variations in a polynomial representation of the force as a function of speed.  27  A photograph of the test set-up appears in Figure 2-9. As can be seen, the A/D card is mounted on the front of the case, the torque meter signal processor is inside, and the computer is fixed on the top.  28  Figure 2-7 A block diagram of the test set up.  29  Figure 2-8 An example of the computer display.  30  Figure 2-9^Equipment layout in the truck.  2.2.2 Torque and speed measurements The torque and speed were measured by a torquemeter which was installed in the drive shaft of the truck. It was a 6-02T noncontact transducer manufactured by S.M. Himmelstein in the U.S.A. A photograph of the torquemeter as installed is presented in Figure 2-10.  31  Figure 2-10 Torquemeter as installed in the truck. Torque calibration was conducted by putting the truck on a constant slope road in the 'park' setting and releasing the brake. This effectively loads the torquemeter with the force acting down the hill. Since torque is proportional to force ( the radius and gearing remaining constant ), a direct calibration of force can be obtained. The set-up is schematically shown by Figure 2-11. To ensure that the truck is placed on an even grade, the angle was measured at each of the four wheels. It is not possible to determine the normal loads at each wheel, since the height of the center of mass is not known. However, this is of no consequence as for calibration the normal force can be readily estimated for the constant gradient at the wheels. This was ensured using a spirit level which showed a deviation of less than 1:400 at the wheels.  33  Velocity calibration was carried out by driving the truck over a known distance at a constant speed. The velocity of the truck was logged by the computer every 0.5 seconds. The average of this result was then compared to the average velocity of the truck, which was determined by the distance divided by the time. Tyre pressure was also noted as to ensure the same setting during future tests. Since the torque and angular velocity of the drive shaft were not measured directly, accuracy of the manufacturer's calibration data cannot be assessed. It was decided to obtain this result independently. To that end, the truck was driven down the road at a constant speed, and the torque and drive shaft angular velocity recorded. Simultaneously the computer logged the velocity and truck drag force. From basic physics, power is equal to both the product of force and velocity, and the product of torque and angular velocity, thereby giving a means of validation. This check showed excellent correlation between the manufacturer's calibration data, and the results given by the present test procedure. 2.2.3 Fuel flow measurement The fuel flow meter that was installed was a micro oval type. It was calibrated by pumping fuel through it and measuring the number of pulses generated for a fixed volume. The calibration confirmed the manufacturers specifications of one pulse per millilitre. Since the truck has a carburettor type fuel system, and other engine options are available for fuel injection, the pressure of the pump exceeds the float buoyancy. Hence a return fuel-line is installed in the vehicle. To account for the fuel flow in the return line for accurate estimation of the fuel consumption there were two options; to install another fuel to measure the amount of  34  fuel being sent back to the tank; or alternatively, the head loss in the supply line could be decreased, so that the pressure supplied to the carburettor was low enough to allow proper functioning of the needle and seat valve. The second option was chosen in the present study. The head loss due to installation of an additional in-line fuel filter and the fuel flow meter was sufficiently high to eliminate the need for a return line at normal operating speeds. It should be noted, however, that at idle the truck does tend to run a little rich. This is deemed to be insignificant.  Figure 2-12  ^  Photograph of the fuel meter installed on the truck.  2.2.4 On-road test procedure  A procedure was developed to ensure that the results obtained during the road-tests were accurate and repeatable. The following is an outline of the procedure used to collect the data on the route described in Table 2-2. It was found that the repeatability and accuracy of the tests were far improved when the tests were performed at night. This gives the  35  advantage of both lower wind levels and reduced road vehicle interference. In addition, a device should be compared with a baseline reference directly, i.e. the baseline test, and the configuration of interest should be tested on the same night. The final four tests of each configuration were done on four nights, with all the three configurations each night: i)  Measure the ambient air temperature and pressure.  Note : This information can be obtained after the test, by noting the time at the start and end of each run, and then calling Environment Canada [(604) 664 9156]. The Vancouver International Airport site is the closest reference point to the test site. ii)  Switch on the power, and ensure that the equipment is in working order using DAMCAL1.EXE. The truck should be parked on level ground, in neutral, with the park brake disengaged. Thus the file created by DAMCALLEXE will also confirm the offsets of the torquemeter.  iii) Run the data logging program (TRUCK.EXE) on the computer. It may be pointed out that mass is a required input for this program. It is designed to have an accelerometer installed in the vehicle to account for changes in velocity and gradient. Acceleration compensation is beyond the scope of this project, but is anticipated in the future work. The mass input for the program, for this stage of the project, is not used, so it  36  does not have to be determined prior to the test. An arbitrary value (say 3400 kg) should be entered to enable the program to run trouble free. iv)  Commence driving, accelerating to a desired speed given in Table 2-2, and hold it constant.  v)  Commence Logging data (note the first satisfactory point). Keep account of any interferences that may be encountered, such as vehicles overtaking and pulling in front, changes in gradient, large trucks either passing, or being passed etc. There should be no significant grade changes in the route indicated in Table 2-2.  vi)  After the desired number of points have been logged, usually 250, note the last recorded point, and adjust the vehicle speed to the next desired level.  vii)  Repeat steps (iv) - (vi) until the test route has been completed as per Table 2-2  Speed zones are listed in the table, and grid references can be located on the map (Figure 2-13). It may be pointed out that no effort was made to obtain a statistical distribution of drag as this would involve a large number of tests with associated fuel costs and time. However, as pointed out later the standard deviation of the CD was within 2.5 %.  37 Table 2-2 Details of the road tests conducted with the full-scale truck configurations. Test & Vehicle Speed  Initial  File No. and Direction  Coord. Coord.  End.  Time  Comments  [s]  File #1 1.1  100 km/hr  E  968387 032874 250  1.2  90 km/hr  E  032874 099874 250  1.3  80 km/hr  E  106873 129357 125  1.4  80 km/hr  W  129357 106873 125  1.5  70 km/hr  W  099874 050874 250  1.6  60 km/hr  W  050874 000874 250  1.7  50 km/hr  W  000874 968387 250  Start test after rise. Start test after rise. Start test after rise. Exit, Stop, and Save.  File #2 2.1  40 km/hr E/N 964397 976414 250  2.2  10 km/hr  N  976414 976423 250  2.3  10 km/hr  S  976423 976414 250  2.4  40 km/hr S/W 976414 964397 250  2.5  30 km/hr E/N 964397 976407 250  2.6  20 km/hr  N  976407 976423 250  3.1  20 km/hr  S  976423 976407 250  3.2  30 km/hr S/W 976407 964397 250  Stop and Save.  File #3 Stop and Save.  38 (Table 2-2  ^  continue)  Test & Vehicle Speed  Initial  File No. and Direction  Coord. Coord.  End.  Time  Comments  [s]  File #4 4.1  50 km/hr  E  968387 000874 250  4.2  60 km/hr  E  000874 042874 250  4.3  70 km/hr  E  050874 099874 250  4.4  80 km/hr  E  106873 129357 125  4.5  80 km/hr  W  129357 106873 125  4.6  90 km/hr  W  099874 032874 250  Start test after rise.  4.7  100 km/hr  W  032874 968387 250  Exit, Stop, and Save.  5.1  110 km/hr  E  968387 050874 250  5.2  110 km/hr  W  050874 968387 250  Start test after rise.  File #5  END OF TEST FOR THIS SET-UP Note: Grid References with an x coordinate greater than 900 refer to map 92G2 and Grid references with an x coordinate of less than 200 refer to map 92G3 of the "Canadian Topographical Maps" 1:50 000  Figure 2-13^Test route map (n.t.s.).  40  Approximately 4000 data points were required to determine the drag characteristics of a given configuration. The estimate was arrived at by experience. Tests undertaken in this thesis have approximately 5500 points to ensure greater accuracy than was obtained by Passmore [16] and also allow a greater time for random factors to even out. This represents logging of 250 points at each of the 11 different speeds in 2 directions. The force on a vehicle is a function of velocity. The function is taken to have the form: F = a o + a i V + a2 V2 , where :^ac, = rolling resistance; a l = viscous drag coefficient in the final drive, combined with the tire drag; a2 = aerodynamic drag coefficient, pAC D/2 Now, from the generalized gas law, p = P/RT Where R = 0.287 kj/kg.K In the present study the torquemeter was calibrated directly for force and velocity as mentioned before. Thus all steady state torque measurements were made with the same device. This combination proved to be the most accurate as zero load transmission losses were automatically accounted for. To process the final data set five different methods were used. These are summarized below:  41  a)  In the first method a polynomial regression program was written (POLYREG.EXE) which used the least squares method of curve fitting. This program gave the velocity coefficients of the force function. A listing of this program appears in Appendix A. The regression analysis was conducted using all the data points, without any preaveraging procedure. Since the test procedure had 22 distinct stages, at an evenly spaced velocity, the regression analysis should be weighted evenly. This was the first procedure used in the data analysis, and it is the simplest. Surprisingly, it is also one of the most accurate.  b)  The second method averaged the force at each of the discrete velocities, thus ensuring far less weighting of a least squares analysis. A program was written to perform the discretisation which is called DSCRT2CL.EXE' and appears in Appendix A. A wide range of speeds must also be tested, with a fairly even distribution of speeds, to maintain accuracy of the regression analysis. Care should be taken to ensure that the same number of points are taken in each speed range, within a 10% tolerance. The preprocessed data served as input to the regression program. The method proved to be somewhat unreliable in its outcome, and is not considered as accurate. It is not recommended for analysing data generated in this form of tests.  c)^As an improvement on the method in (b), all velocities with less than 50 data points were removed prior to the regression  42  analysis. The removal of points was undertaken using a spreadsheet program. This resulted in some improvement, however, the results were still not as reliable as those generated in the test procedure (a). d)  The next analysis procedure was to take a time averaged sample to get an average force for a particular average speed. This procedure was implemented with 10, 25, and 250 second time averaged samples. Each of these then served as input to the polynomial regression program. The 250 point time average proved to be the most accurate. It gave 2 sets of 11 equally spaced points from 10 to 110 km/hr. To preform this procedure 'TAVG.EXE' program was written, which is listed in Appendix A Method (d) provided the best results compared to the earlier procedures. The consistency of the test can be shown by comparing the 10, 25, and 250 s time averaged results. Ideally, if the tests were perfect, these results should coincide. In most cases, the discrepancy was less than one percent.  e)  The final method of analysis, and the one which is used to here is a modification of the one given in (d). To begin with, the average force coefficients for both rolling resistance and internal brake, and viscous drag were averaged for 24 tests. These nonaerodynamic forces were then removed from each data point, leaving only the aerodynamic force. Since the aerodynamic resistance is proportional to the square of the  43  velocity, the velocity terms were converted to m/s and squared. Following this a linear regression analysis, with zero offset, was performed to determine the coefficient for the aerodynamic term. The worst standard deviation over 4 tests was 2.5%. This procedure was implemented using the 'TAVGRM.EXE' program which appears in Appendix A This method was found to be the most accurate. It gave a standard deviation for most configurations of approximately 2.5 %. It involves the assumption, made at the start of the test-program, that a change in the shape of the truck, only affects the aerodynamic term. Thus it gives a realistic comparison of forces between the two cases. During the road tests, difficulties at times did arise in separating the viscous term from the aerodynamic drag. For example if the tests are being conducted in a relatively windy condition, the viscous drag contribution appears to be larger. This is because the effective yaw angle of the vehicle decreases as the vehicles speed increases. Now the CD value decreases with an increase in speed, thus making the forces more linear with respect to the velocity. Care was taken to avoid high winds as much as possible. To minimize the effects of turbulence, the last set of four tests for each configuration was carried out at night, between 10 p.m. and 5 a.m., and a qualitative measure of the wind was noted by several flags on the test-route. The fence performance proved to be somewhat speed dependant. This resulted in a much lower, and some times negative viscous term, whilst the aerodynamic drag term actually increased. It seems logical to  44  expect that the CD of the truck depends on the velocity. The normal second order polynomial regression does not take this into account. The only way that the regression analysis can account for this variation is by modifying both the viscous, and aerodynamic drag terms of the equation. To reduce the effect of the speed dependency, the method described in (e) was adopted.  45  3 RESULTS AND DISCUSSION 3.1 Wind Tunnel Model tests 3.1.1 Wind tunnel models with fences The wind tunnel model was tested with various arrays of fences. The model had a baseline drag coefficient CD0  = 1.43. Initially only vertical  fences were installed on the model, these gave a drag reductions of 12.5 % for an optimal height (h f Id) of 0.054. When a horizontal fence is added to the two vertical fences configuration the drag coefficient decreased to 1.03, a 28.0 % reduction based on the reference case. Extensions were then added to the horizontal fence, so that it reached the full truck width, and again there was improvement in the performance (C D of 0.999, a total reduction from the baseline of 30.1 %). A second horizontal fence continued the trend and further reduced the drag slightly, to 0.981, i.e. a decrease of 31.4 % !. Figures 3-1 through 3-5 detail the progression through these sequences of fence configurations. It was decided that the additional fourth fence would not be used on the full-scale truck as it gave only a 1.3 % improvement over the three fence case. Furthermore the road test error would be, perhaps, larger than this.  1.4  1.35  1.3  Co  hf/d • 0.081 1.25  h f /d ■ 0.054 hf/d • 0.030  1.2  bfv/d ■ 0.43 R n ■ 2x10 5 CDos 1.43  1.15 0.25  0.3  0.35  0.4  xf /d Figure 3 1 Wind tunnel test results for the cube-van model (1/6 scale) to determine optimum locations of vertical fences 1 and 2. -  0.45  1.3 (hf /d)cr = 0.054  1.25  (xf /d)cr = 0.38  b fv /d = 0.43 1.2  R n a 2x10 5 CDo" 1.43  CD 1.15  1.1  1.05  1 0.12  0.14  0.16^0.18  0.2  y if3 /d Figure 3-2 Wind tunnel test results for the cube-van model to determine  optimum location of horizontal fence 3.  0.22  Figure 3-3 Wind tunnel test results for the cube-van model with one horizontal and tow vertical fences. Note the horizontal fence extends to the entire width of the van.  CD  id  Yf4 Figure 3-4 Wind tunnel test results for the cube-van model with two horizontal and two vertical fences.  51  3.1.2 Wind tunnel model with a rotating cylinder and fences A rotating cylinder was installed in kit form, so as to be comparable to a similar configuration suitable for the full-scale truck, on the front of the cube. The kit contained the cylinder, drive motor, and the speed monitoring and control system. Being located outside it does not infringe on the payload space. The kit position, which controls the projection of the cylinder in to the free stream, and the cylinder speed were varied systematically to establish favourable operating conditions. The results, presented in Figure 3-6, clearly show that there is an optimum position of the kit (li k /d = -0.021). As expected, for a given position of the kit, injection of momentum through the cylinder rotation is to delay separation of the boundary-layer from the top face of the van which, in turn, is reflected in the drag reduction. For U, /U = 3 and the optimum kit location corresponding to li k /d = -0.021, the change in CD from 1.24 to 1.03 represents a drag reduction of around 28%, essentially the same as than given by the fences. Note, any further increase in the U, /U does not result in significant improvement in the performance.  1.4 ^ Hkici • -0.021 Li Hk /d • 0  Hk/d • 0.021  Hk/d ■ 0.042 A H k /d ■ 0.064^Hk/d ■ 0.085  1.3  11111111111  Uc z  CD  U 1.2  Rn • 2x10 5  • 1•■ • •^• • 1116.S^MOM.  1.1 MN  1  0^0.5^1  ^  1.5^2^2.5  3  ^ ^ ^ ^ 4.5 4 3.5 3  /U Figure 3-6 Effect of momentum injection and kit position on the drag reduction of the cube-van model.  53  As the kit provided a flat area exposed to the free stream, it was tempting to introduce fences. With two vertical fences and U, /U = 2, a reduction in CD by 41.3 % (based on the original nonkit configuration) is rather astounding. Of course, MSBC is not a passive device as the fence and would involve expenditure of energy through the drive system. These results are presented in Figures 3-7 and 3-8.  1.3 h f /d ■ 0.02 • h f /d R 0.04 1.2  h f /d R 0.06 h f /d ■ 0.08  CD  h f /d ■ 0.10  1.1  1  0.9 ^ ^ ^ ^ ^ 0.3 0.32 0.34 0.36^0.38 0.4 0.42^0.44 Xf id Figure 3-7 Effect of the height and spacing of the two vertical fences on the drag of the cube-van model. Note, the kit is in its optimum orientation, however, the cylinder is not rotating. Of course, the rounded upper leading edge presented by the cylinder would contribute to the drag reduction.  1.3 • ^  1.2  1.1  hf/d • 0.08 h f /d • 0.10 R n = 2=10 5  U  H k /d ■ -0.02 CDo  C.  8  1 . 19  0.9  0.8  0.7 ^ 0  1  ^  2  3  4  UciU Figure 3-8 Effect of the cylinder rotation on the drag of the cube-van in the hybrid MSBC/fence configuration.  56  3.2 Full Scale Tests The baseline (i.e. reference configuration devoid of fences and MSBC) tests were conducted on the cube-van as supplied by GMC, with a Grumman Olsen body and the extended roof. The extension was built by Intercontinental Truck Body (B.C.) Inc. and raised the roof of the truck by 600 mm. The raised roof simulates a vast number of larger, customised, trucks, with bigger chassis, that often use drag reducing devices. The truck without its extended roof had a CD of 0.40. However, once the extension was placed on the vehicle the CD increased to 0.610, this represented 75.25 % of the total force exerted by the engine to propel the truck at 100 kph. With the a horizontal fence installed there was only a small change in the drag coefficient (C D = 0.614). Note, this represents a 0.65 % drag increase. Of course, with the standard deviation of the data for the horizontal fence configuration being 2.5 %, and that for the extended roof at 2.4 %, it is clear that the result represents no net change. However, the situation changed dramatically with the addition of two vertical fences. Now CD reduced to 0.524, a decrease of aerodynamic resistance by 16.6 %. Indeed this is quite significant, representing a drop in power demand of 11.1% and the corresponding reduction in the fuel consumption of 9.6 % as an average over the speed range. The results showed that the reduction of fuel consumption was far more noticeable at higher speeds. In the speed range of 90 - 110 kph, it amounted to around 25.1 %. Since this represents the highway speed range at which most trucks travel, the financial benefits are enormous. The Fences enabled the vehicle to operate in a higher gear, and hence the fuel savings not only came from the fact that the engine was not required  57  to deliver as much force, but it could deliver the required force at much lower engine speeds. A factor which may contribute to the uneven reduction in the fuel consumption is the Reynolds number. CD may be a function of velocity over the range tested, and hence the change in force would vary with speed. The time averaged force data with polynomial regression are compiled in Appendix B. Each plot has the test name and number. The tests are numbered in the reverse chronological order. All tests with a given number were performed on the same day/night. Time averaged fuel data appears in the same format in Appendix C. A summary of the force regression in Table 3-1. It should be noted that tests 1 to 4 were performed at night, and hence as expected the baseline (extended roof case) drag values are higher compared to those obtained for the tests performed during the day. Watkins [13] found the CD to decrease with and increase in the longitudinal turbulence intensity. It is of interest to recognize that performance of the fences deteriorates at lower speeds (< 30 kph, Figure 3-10). In fact, the results showed increase in CD. This would suggest that, at a lower speed, the fluid is unable to clear the fences, i.e. it is blocked by them and remains stagnant, resulting in an increase in pressure and a corresponding increase in drag. Fortunately, the increase in fuel consumption is rather small as the nominal demand itself is rather low at lower speeds.  58  The force was normalized to the weight of the vehicle in Figure 3-9a. This was done because the drag forces had two nonaerodynamic terms which contribute approximately one third of the total force at 100 kph and significantly more at lower speeds. Alternatively the force can be normalized to the dynamic pressure times the frontal projected area ( q.A), and this result appears in Figure 3-9b. The horizontal lines in figure 3-9b represent the CD value that the curves asymptotically approach. Each line-type represents one set-up, both in the curves, and the asymptotes.  59  Table 3-1 Results based on the road test data  Test  Test type  No. 1  2  3  4  5  6  7  V2  Ambient  Barometric  Coefficient  Temperature  Pressure  kg/m  0C  kPa  CD  ext. roof  2.90  8.2  102.12  0.62  hor. fence  2.87  9.4  101.98  0.61  all fences  2.43  11.4  101.91  0.52  ext. roof  2.75  7.3  101.30  0.59  hor. fence  2.97  9.0  101.27  0.64  all fences  2.53  7.9  101.19  0.54  ext. roof  2.85  10.4  102.25  0.61  hor. fence  2.85  11.3  102.21  0.61  all fences  2.47  10.4  102.25  0.53  ext. roof  2.90  12.5  101.75  0.63  hor. fence  2.76  12.6  102.25  0.60  all fences  2.30  14.5  101.64  0.50  ext. roof  2.48  20  101.84  0.55  hor. fence  2.47  20  101.84  0.55  ext. roof  2.49  22  101.35  0.56  hor. fence  2.46  22  101.35  0.55  ext. roof  2.47  23  101.84  0.55  hor. fence  2.47  23  101.84  0.55  60 Table 3-1 Results based on the road test data V2  Ambient  Barometric  Coefficient  Temperature  Pressure  kg/m  0C  kPa  ext. roof  2.79  20  102.29  0.62  hor. fence  2.59  20  102.29  0.58  9  ext. roof  2.30  28  101.67  0.53  10  ext. roof  3.07  20  101.64  0.68  11  ext. roof  2.92  22  102.11  0.65  12  ext. roof  2.93  15  101.34  0.64  Test  Test type  No. 8  CD  ^  0.12^ 0.100.080  2 0.06L  0.040.02  -  ^0.00^ 0  20  40^do^80^lb()  Velocity [km/hr] Figure 3-9a Comparative force regression analysis showing the effect of fences.  120  Figure 3-9b Comparative force regression analysis showing the effect of fences in terms of CD.  64  3.3 Comparison Between Model and Full Scale Test The wind tunnel tests with a 1/6 scale model of the cube-truck provided encouraging performance of fences in reducing the drag through tripping of the boundary-layer. Of course, ultimate validity of the concept is assessed through tests in the operating environment as accomplished here through the road tests using a full-scale prototype truck. Due to idealized character of the wind tunnel tests, discrepancy between the wind tunnel and the road tests results can be expected. In the present study, the wind tunnel tests predicted the drag reduction of around 31.4 % under optimum fence configuration, however, during the road tests the peak reduction of 16.6 % was realized. Suck a deviation was anticipated and can be explained quite readily: (i)  At the outset, as pointed out before, the rather idealized character of the wind tunnel tests must be recognized. It does not account for the free stream turbulence, road boundary-layer, and yaw condition of the real-life situation. Furthermore, the Reynolds number is smaller by around two orders of magnitude compared to that of the full-scale truck.  (ii)  The wind tunnel model, being based on an earlier version, is significantly different from the actual cube-van used during the road tests. The main differences lie in the hood design, and sharp corners present in the plexiglass wind tunnel model, while all the corners and edges of the truck were rounded. Obviously this would give the prototype truck a relatively small reference (i.e. baseline) drag coefficient. In fact, wind tunnel tests were conducted incorporating rounded  65  edges in the model with a baseline drag dropping form 1.43 to 1.09 (Figures 3-11, 3-12). Note, with the rounded corners and horizontal-vertical fences, the CD of 0.82 for optimum configuration (Figure 3-12) corresponds to a reduction in aerodynamic resistance of 24.8 %. This is closer to the roadtests result of 16.6 % in spite of the difference in geometry and idealized test conditions as mentioned before. (iii)  Scaling of fences and their orientation for full-scale application were also approximate. Dimensions of the fences were geometrically scaled, so was their orientation. For preciseness, they should have been based on the hydraulic diameter. Furthermore, the truck geometry being different, the optimum location of the fences is still not arrived at. Thus there is a possibility of improvement in the drag reduction through optimized positioning of the fences.  (iv)  The wind tunnel tests, in the optimized situation involved four fences, two horizontal and two vertical. On the other hand, so far, the road tests have been conducted only with three fences, two vertical and one horizontal. In an earlier study by Ying [2], with a different geometry of the truck, addition of the force fence made further significant reduction in the drag (by around 4-5 %).  (v) Yet another factor that would affect correlation between the model and the full-scale road test results would be due to differences in the flow under the truck, which can contribute significantly to the drag. In the present case, the bottom of  66  the model was made of smooth plexiglass and the tunnel floor was of wood. On the other hand, the undercarriage of the cube-van has a complex geometry with drive shaft, torquemeter and other components of the transmission assembly. Considering the above factors, the trends suggested by the wind tunnel tests are indeed valuable and accurate.  1.2 hf/d = 0.057 1.15  h f /d = 0.085 h f /d • 0.106  1.1  R n • 2.0*10 5 C DO • 1.09  CD 1.05  1  0.95  0.9 0.26  0.3 ,  0.34  Xfid  0.38  Figure 3-11^Wind tunnel test results for the cube-van model with  rounded corners and vertical fences.  0.42  0) as  69  4 CONCLUDING REMARKS 4.1 Summary of Results 4.1.1 Wind tunnel model tests Based on a rather fundamental study of both the Moving Surface Boundary-layer Control and trip-fences with a cube-van model the following general conclusions can be made: (i)  MSBC and trip fences are both successful at reducing drag when applied to a cube-van model.  (ii)  With the fences, the drag reductions were 31.4 % for a model with sharp edges and 24.8 % for the model with rounded edges. This suggested considerable promise for the concept and need for full-scale tests.  (iii)  Fences appear to be a promising, cost effective way of reducing drag on the baseline model, regardless of whether it has curved or straight edges.  (iv)  Application of the MSBC through a rotating cylinder kit resulted in a drag reduction of around 28 %. Its hybrid application in conjunction with the fences led to a surprising result of a decrease in aerodynamic resistance by 41.3 %.  (v) The power demanded by the MSBC procedure is relatively small. In the present study with the 1/6 scale models, it amounted to around 90 W.  70  (vi) The entirely passive character of the fences, their simplicity and ease of application are indeed quite attractive features conducive to full-scale application.  4.1.2 Full scale tests (i)  In general, the full-scale tests with the fences substantiate the positive influence of the fences in reducing drag.  (ii)  Although the trends are accurate, there is a discrepancy between the prototype and the model results. This is attributed to significant differences between the model and road-tests conditions.  (iii)  A decrease in drag coefficient by 16.6 % with two vertical and one horizontal fences is indeed impressive. It represents a reduction in the power demand by 11.1 % with a decrease in fuel consumption of around 9.6 %, the average over the speed range used during the tests.  (iv)  Due to differences between the prototype and the model, the fence geometry and orientations are not yet optimum. Hence, there is a scope for further improvement in the performance.  (v) As the fuel consumption would depend on the speed of operation, the 11.1 % reduction in power with the application of fences would now permit use of the overdrive instead of 3rd gear. For the truck negotiating flat terrain at 100 kph, with overdrive, the reduction in fuel consumption amounts to around 39.6 % (Figure 3-10). Of course in actual practice, the net benefit would be significantly  71  smaller due to energy expended during acceleration, braking, negotiation of the gradient, decent,etc. (vi)  The tests account for the yaw effect only in an average fashion. Performance of the fences at various yaw orientation has not been established systematically. ^Fortunately, as pointed out by Drollinger [16], most trucks spend a large portion of their time at yaw angles of less than 4 0 (only a 10 % probability of yaw angles greater than 4 0 for commercial trucks). Hence the results are not likely to be affected significantly by the presence of yaw.  (vii)  The fuel consumption results showed considerable fluctuations and presented some difficulty in the curve-fitting. Engagement and disengagement of gears would contribute to it, however, they may not completely account for the variations.  4.2 Recommendation for future study The investigation reported here represents only the first step in studying this exciting, challenging and promising phenomenon of the flow control over a three-dimensional truck. There are a number of aspects which demand further attention. Only a few of the more significant areas requiring further study are indicated below: (i) Wind tunnel test arrangement needs improvement with reference to the model support system, instrumentation, simulation of the ground boundary-layer as well as geometric accuracy of the model. A systematic study to asses the effect of the Reynolds number, free stream turbulence and yaw angle of the model would also provide useful information.  72  (iii)  Hybrid fence configurations with deflectors and MSBC need more systematic further study.  (iv)  A cruise control unit should be installed in the cube-van. This would improve measurement of force as well as reduce fluctuations in the fuel consumption data.  (v) An accelerometer should be installed to account for variation in the speed during acceleration, braking, negotiation of gradients, etc. Provision for it has been made in the present hardware as well as software, so its incorporation would be quite simple. This would also permit precise determination of the energy expended during braking and the effect of truck-load on it.  73  REFERENCES [1]  Van Setters, R., Service Manager, Intercontinental Truck Body Inc., B.C., Canada, 1992.  [2]  Ying, 0.B., "Boundary-layer Control of Bluff Bodies with Application to Drag Reduction of Tractor-Trailer Truck Configurations", M.A.Sc Thesis, University of British Columbia, December 1991.  [3]  Sovaran, G., Morel, T., and Mason, T. W. Jr., "Aerodynamic Drag Mechanisms of Bluff Bodies and Road Vehicles", Proceedings of the Symposium held at the General Motors Research Laboratories, Plenum press, New York, 1978.  [4]  Koernig-Facsenfeld, F.R., "Aerodynamik des kraftfahrzeugs: Verlay der Motor-Rundschau", Umshau Verlag, Frankfurt, West Germany, First Edition, 1951, Reprinted 1980.  [5]  Kramer, C., and Gerhardt, H. J., "Road Vehicle Aerodynamics", Proceedings of the 4th Colloquium on Industrial Aerodynamics, Aachen, June 1980.  [6]  Kurtz, D.W., "Aerodynamic Design of Electric and Hybrid Vehicles: A Guidebook", U. S. Department of Energy, Report No. 5030-471, September 1980.  [7] Bearman, P.W., "Review of Bluff Body Flows Applicable to Vehicle Aerodynamics", Transactions of the ASME, Journal of Fluid En , Vol. 102, September 1980, pp 265-274.  74  [8]  Wacker, T., "A Preliminary Study of Configuration Effects on the Drag of a Tractor-trailer Combination", M.A.Sc. Thesis, University  of British Columbia, Vancouver, Oct. 1985. [9]  Tyrrell C. L., "Aerodynamics and Fuel Economy - On Highway experience." Proceedings of the Truck and Bus Meeting and  Exposition, Dearborn, Michigan, November 16 - 19, 1987, Society of Automotive Engineers, No. 872278 [10]  Buckley, F. T. Jr, "An Improved over the road test method for Determining the Fuel Savings benefit of a truck aerodynamic device", Proceedings of the International Congress and Exposition, Detroit, Michigan, February 25 - March 1, 1985, Society of Automotive Engineers, No. 850285  [11]  Saunders, J.W., Watkins, S., Hof man, P., and Buckley, F. T. Jr, "Comparison of On-Road and Wind Tunnel Tests for Tractor Trailer Aerodynamic Devices, and Fuel Savings Prediction." Proceedings of  the International Congress and Exposition, Detroit, Michigan, February 25 - March 1, 1985, Society of Automotive Engineers, No. 850286. [12]  Watkins, S., Saunders, J.W., and Hoffman, P.H., "Wind Tunnel Modelling of Commercial Vehicle Drag Reducing Devices: 3 Case Studies", 1987, Society of Automotive Engineers, No. 870717.  [13]  Eaker, G.,"Wind Tunnel-to-Road Aerodynamic Drag Correlation",  Proceedings of the International Congress and Exposition, Detroit, Michigan, February 29 - March 4, 1988, Society of Automotive Engineers, No. 880250.  75  [14]  Remenda, B.A.P., Krause, A.E., and Hertz, P.B., "Coastdown Resistance Analysis Under Windy and Grade-Variable Conditions", Proceedings of the International Congress and Exposition, Detroit, Michigan, February 27 - March 3, 1989, Society of Automotive Engineers, No. 890371.  [15]  Passmore, M.A., Jenkins, E.G., "A Comparison of the Coastdown and Steady State Torque Methods of Estimating Vehicle Drag Forces", Proceedings of the International Congress and Exposition, Detroit, Michigan, February 29 - March 4, 1988, Society of Automotive Engineers, No. 880475  [16]  Drollinger, R.A., "Heavy Truck Aerodynamics", Kenworth Truck Co., 1987, Society of Automotive Engineers, No. 870001.  [17]  Inagawa, M., Ohta, M., "Contribution of Vehicular Parameters on Fuel Economy of Trucks", 1985, Society of Automotive Engineers, No. 852257  [18]  Goldstein, S, "Modern Developments in Fluid Mechanics", Vols. I and II, Oxford University Press, 1938  [19]  Lachmann, G. V., "Boundary-layer and Flow Control", Vols. I and II, Pergamon Press, 1961  [20]  Rosenhead, L., "Laminar Boundary-layers", Oxford University Press, 1966  [21]  Schlichting, H., "Boundary-layer Theory", McGraw Hill Book Company, 1968  76  [22]  Chang, P. K., "Separation of Flow", Pergamon Press, 1970  [23]  Favre, A., "Contribution a l'Etude Experimentale des Mouvements Hydrodyamiques a Duex Dimensions", Thesis presented to the University of Paris, 1938.  [24]  Alvares-Calderon, A., and Arnold, F.R., "A Study of the Aerodynamic Characteristics of a High Lift Device Based on Rotating Cylinder Flap", Stanford University Technical Report RCF-1, 1961.  [25]  Cichy, D.R., Harris, J.W., and MacJat, J.K., "Flight Tests of a Rotating Cylinder flap on a North American Rockwell YOV-10A Aircraft", NASA CR-2135, November 1972.  [26]  Weiberg, J.A., Giulianettij, D., Gambucci, B., and Innis, R.C., "Take-off and Landing Performance and Noise Characteristics of a Deflected STOL Airplane with Interconnected Propellers and Rotating Cylinder Flaps", NASA TM X-62, 320, December 1973.  [27]  Cook, W.L., Mickey, D.M., and Quigley, H.G., "Aerodynamics of Jet Flap and Rotating Cylinder Flap STOL Concepts," AGARD Fluid Dynamics Panel on V/STOL Aerodynamics, Delft, N \Netherlands, April 1974, Paper No. 10.  [28]  Johnson, W.S., Tennant, J.S., and Stamps, R.E., "Leading Edge Rotating Cylinder for Boundary-layer Control on Lifting Surfaces", Journal of Hydrodynamics, Vol 9, No. 2, April 1975, pp. 76-78.  [29]  Modi, V.J., Sun, J.L.C., Akutsu, T., Lake, P., McMillan, K., Swinton, P.G., and Mullins, D., "Moving Surface Boundary-layer Control for  77  Aircraft Operation at High Incidence", Journal of Aircraft, AIAA, Vol.18, No. 11, November 1981, pp. 963-968. [30]  Mokhtarian, F., and Modi, V.J., "Fluid Dynamics of Airfoil with Moving Surface Boundary-layer Control", AIAA Atmospheric Flight Mechanics Conference, August 1986, paper No. 86-2184-CP; also Journal of Aircraft, Vol 25, No. 2, February 1988, pp 163-169.  [31]  Mokhtarian, F., Modi V.J., and Yokomizo, T., "Rotating Air Scoop as Airfoil Boundary-layer Control", Journal of Aircraft, AIAA, Vol. 25 No. 10 October 1988, pp. 973-975.  [32] Mokhtarian, F., Modi V.J., and Yokomizo, T., "Effect of Moving Surfaces on the Airfoil Boundary-layer Control", AIAA Atmospheric Flight Mechanics Conference, Minneapolis, Minnesota, August 1988, Paper No. AIAA-88-4303CP; also Proceedings of the Conference, Editors: R. Holdway and B.Kaufman, AIAA Publisher, pp. 660-668; also Journal of Aircraft, AIAA, Vol 27, No. 1, January 1990, pp 44-60.  78  APPENDIX A : PROGRAM LISTINGS Data Logging Program #include <stdio.h> #include <graphics.h> #include <stdlib.h> #include <conio.h> #include <time.h> #include <dos.h> #include <string. h> #include <bios.h> #include <stdlib.h> /* GLOBAL VARIABLES */ float mass; /* CONSTANTS */ const float rho =1.2; const float fuelrho= 0.00075; const int xmax=120, ymax=4000; char *comm="CE0A1,3 ; /* setport() is used to set up the port and initiate communications with the dam */ setport() {char o[100]; int p; bioscom(0,227,0); p=0; do{ bioscom(1,0x0d,0); p++; o[p]=bioscom(2,NULL,0);}while(o[p]!=0x3e && p <200);} /* getdata() asks the dam for data when called */ getdata(data) int data[20]; {int q,p; char o[100],*r; p=0; for(q=0;q<strlen(comm);q++)bioscom(1,comm[q],0); for(q=0;q<6000;q++); do{ if(p!=0)bioscom(1,0x00,0);p++;o[p]=bioscom(2,NULL,0); }while(o[p]!=0x3e && p <200); r=strtok(o,"-");  79 for(p=0;p<20;p++){ data[p]= atoi(r); r=strtok('\0',":-. ");}} coefdet(force,speed,size) float *force, *speed; { /* coefdet determines the coefficients to the third order by means of the least squares method. float a[8],d,cd,cv,cr; int i,j; char cdc[10],cvc[10],crc[10];  for(i=1;i<=7;i++) a[i]=0; for(i=1;i<=size;i++){ a[1 ]=a[ 1 ]+speed[i]/3.6; a[2]=a[2]+speed[i]*speed[i]/12.96; a[3]=a[3]+speed[i]*speed[i]*speed[i]/46.656; a[4]=a[4]+speed[i]*speed[i]*speed[i]*speed[i]/167.9616; a[5]=a[5]+force[i]; a[6]=a[6]+force[i]*speed[i]/3.6; a[7]=a[7]+force[i]*speed[i]*speed[i]/12.96;) d= size*(a[2]*a[4]-a[3]*a[3])-a[1]*(a[1]*a[4]-a[2]*a[3])+a[2]*(apra[3]-a[2]*a[2]); cr=(a[5]*(a[2]* a[4]-a[3]*a[3])-a[1]*(a[6]*a[4]-a[7]*a[3])+a[2]*(a[6]*a[3]-a[7]*a[2]))/d; cv=(size*(a[6]*a[4]-a[7]*a[3])-a[5]*(a[1]*a[4]-a[2]*a[3])+a[2]*(a[1]*a[7]-a[2]*a[6]))/d; cd=(sizela[2]*a[7]-a[3]*a[6])-a[1]*(a[1]*a[7]-a[2]*a[6])+a[5]*(a[1]*a[3]-a[2]*a[2]))/d; cd=cd/(0.6*6.631); cv=cv;^cr=cr/(mass*9.8); gcvt(cd,4,cdc);^gcvt(cv,4,cvc); gcvt(cr,3 ,crc); outtextxy(40,27,"Cd ="); outtextxy(87,27,cdc); outtextxy(40,42,"Cv ="); outtextxy(87,42,cvc); outtextxy(40,57,"Cr ="); outtextxy(87,57,crc);}  /* axis draws, and lables the axis for the test */ axis(xmax,ymax) { char x[10],y[10]; int driver=VGA, mode=VGAHI; itoa(xmax,x,10); itoa(ymax/1000,y,10); initgraph(&driver,&mode,""); line(25,450,610,450); line(30,455,30,30); line(610,450,610,455); line(25,30,30,30); outtextxy(5,465,"(0,0)"); outtextxy(2,27,y); outtextxy(603,460,x); settextstyle(DEFAULT_FONT, VERT_DIR, 1); outtextxy(15,200,"FORCE [kN]"); settextstyle(DEFAULT_FONT, HORIZ_DIR, 1); outtextxy(250,470,"TRUCK SPEED [km/hr]");  80 outtextxy(40,72,"Fuel ="); outtextxy(40,87,"Mass ="); outtextxy(40,102,"Logged :"); } box(int x, int y, int color){ setcolor(color); line(x-1,y-1,x+1,y-1); line(x+1,y-1,x+1,y+1); line(x+1,y+1,x-1,y+1); line(x-1,y+1,x-1,y-1);} main() ( char ans[30],f1[10],ms[10],dp[10]; float force[2001], speed[2001], time[2001]; float accl,totfuel, fcal, foff, velcal, veloff; int fv, velv, i,j, size, xpixel, ypixel; int fuel, data[20]; int rawfuel[2001], rawtorque[2001], rawvel[2001], rawacc1[2001]; FILE *fpraw,*fpcal; clrscr(); printf("\n\n^TRUCK : DATA LOGGING PROGRAM\n\n"); prinff("Please ensure that the setup of the lap top is set to:\n"); printf(" 1) Screen ALWAYS ON\n 2) Hard drive at 1 MINUTE\n\n"); prinff("Loading Calibration data\n"); ^ if((fpcal=fopen("C:\\PROJECT\\PROGS\\CAL.DAT ","r"))==NULL)(printf("cannot open calibration file\n");exit(1);} fscanf(fpcal,"%f %f %f %f",&fcal,&foff,&velcal,&veloff); fclose(fpcal); prinff("Initialising DA/M 100\n"); setport(); prinff("Initialisation Complete\n"); prinff("input raw data file name =>"); scanf("%s",ans); if((fpraw=fopen(ans,"a+t"))==NULL){prinff("cannot open file\n");exit(1);} prinff("input vehicle mass =>"); scanf("%f",&mass); i=0; fuel=0; xpixel=-20; ypixel=-20; axis(xmax,ymax); outtextxy(100,10,"Hit any key to start data logging"); getchar(); getchar(); setcolor(BLACK);outtextxy(100,10,"Hit any key to start data logging"); do{ do(if(i>(2001-120))printf("\a");}while(biostime(0,0)<18); biostime(1,0); getdata(data); setcolor(BLACK);outtextxy(107,72,f1);outtextxy(107,87,ms); outtextxy(107,102,dp); velv=data[7]; fv=data[6]; fuel+=data[5]; accl=data[8]; acc1=0; /* REMOVE WHEN ACCELEROMETER INSTALLED */  81 totfuel = fuel*fuelrho; rawfuel[i] =data[5];rawtorque[i] =data[6]; rawvel[i] =data[7];rawaccl[i] =data[8]; time[i] =data[1]*3600.0+data[2]*60.0+data[3]+data[4]/1000.0; force[i]=fvical+foff-acct* (mass-totfuel); speed[i]=velv*velcal+veloff; box(xpixel,ypixel,BLACK); xpixel=speed[i]*580/xmax+30; ypixel=450-force[i]*420/ymax; box(xpixel,ypixel,WHITE); putpixel(xpixel,ypixel,WHITE); setcolor(WHITE); gcvt(fue1,6,f1);outtextxy(107,72,f1); gcvt(mass-toffue1,6,ms);outtextxy(107,87,ms); gcvt(i,5,dp);outtextxy(107,102,dp); i++;}while(!bioskey(1)); outtextxy(100,10,"Hit any key to store data"); getchar(); getchar(); for(j=0;j<=i;j++){ fprintf(fpraw,"%i^%f^%d^%d^%d^%d^%f^%f\n" ,j,time[j],rawfuel[j],rawtorque[j],rawvel[j],rawaccl[j],speed[j],force[j]);} fprintf(fpraw,"\n\n%d %f",fuel,mass-totfuel); coefdet(force,speed,i); setcolor(BLACK);outtextxy(100,10,"Hit any key to store data"); setcolor(WHITE);outtextxy(100,10,"Hit any key to termintate this program"); getchar(); getchar(); fclose(fpraw);}  Polynomial Regression Program  #include "stdio.h" int size; float force, speed; float a[8],d,cd,cv,cr; int i,size; char fn[30]; main(){ FILE *fpin; clrscr(); printf("\n\n^POLYREG : 2ND ORDER POLYNOMIAL REGRESSION\n\n"); printf("This program is designed to take velocity-force data and perform a\n"); printf("regression on it. The velocity data should be in km/hr as this program\n"); printf("will automatically convert it to m/s. This velocity conversion makes\n"); priptf("this program unsuitable for other curve fitting.\n\n"); printf("Input data file name =>");  82 scanf("%s",fn); if((fpin=fopen(fn,"r"))==NULL){printf("cannot open input file\n");exit(1);} fscanf(fpin,"%i",&size); printf("\n\nThe data field contains %i points\n\n\n",size); for(i=1;i<=7;i++) a[i]=0; for(i=1;i<=size;i++){ fscanf(fpin,"%f %f",&speed,&force); a[1]=a[1]+speed/3.6; a[2]=a[2]+speed*speed/12.96; a[3]=a[3]+speed*speed*speed/46.656; a[4]=a[4]+speed*speed*speed*speed/167.9616; a[5]=a[5]+force; a[6]=a[6]+force*speed/3.6; a[7]=a[7]+force*speed*speed/12.96; ) d= size*(a[2]*a[4]-a[3]*a[3])-a[1]*(a[1]*a[4]-a[2]*a[3])+a[2]*(apra[3]-a[2]*a[2]); cr=(a[5]*(a[2]* a[4]-a[3]* a[3])-a[1]*(a[6]*a[4]-a[7]*a[3])+a[2]* (a[6]*a[3]-a[7]* a[2]))/d; cv=(size*(a[6]*a[4]-a[7]*a[3])-a[5]*(a[1]*a[4]-a[2]* a[3])+a[2]*(a[1]*a[7]-a[2]*a[6]))/d; cd=(size*(a[2]*a[7]-a[3]* a[6])-a[1]*(a[1]*a[7]-a[2]*a[6])+a[5]* (a[1]*a[3]-a[2]*a[2]))/d; printf("The result is of the form: R + k.v + D.v^2, where\n\n"); prinff("R = %15.5f ; k = %15.5f ; D = %15.5f\n",cr,cv,cd); printf("\nTherefore at 30 m/s F = °/08.0f\n",cr+30*cv+900*cd); }  Discretization Program  #include <stdio.h> #include <math.h> float a, vs[131][2], fcal, foff, velcal, veloff; int b,vel; int i,size, v[131][2]; char fn[30]; main(){ FILE *fpin, *fpout, *fpcal; clrscr(); printf("\n\n^DSCRT2CL : AVERAGING FORCES AT DISCRETE SPEEDS\n\n\n"); prinff("Loading Calibraiton data\n"); if((fpcal=fopen("C:\\TC\\CALDAT ","r"))==NULL){printf("cannot open calibration file\n");exit(1);) fscanf(fpcal,"%f %f %f %f",&fcal,&foff,&velcal,&veloff); fclose(fpcal); printrnInput data file name =>"); scanf("%s",fn); if((fpin=fopen(fn,"r"))==NULL){printf("cannot open input file\n");exit(1);} prinff("\nInput sorted file name =>"); scanf("%s",fn); if((fpout=fopen(fn,"w"))==NULL){printf("cannot open sorted file\n");exit(1);) fscanf(fpin,"%i",&size); prinff("\n\nThe data field contains %i points\n\n\n",size);  83 for(i=1;k131;i++){ v[i][0]=0; v[i][1]=0; vs[i][0]=0; vs[i][1]=0;) for(i=1;i<=size;i++){ fscanf(fpin,"%i %i",&b,&vel); v[vel][0]+=b; v[vel][1]+=1;) for(i=1;i<131;i++){ if(v[i][1]!=0)vs[i][0]=1.0*v[i][0]/v[i][1];) rewind(fpin); printf("\nmeans calculated \n"); fscanf(fpin,"%i",&b); for(i=1;i<=size;i++){ fscanf(fpin, Kyo, / &b,&vel); vs[vel][1]+=(b-vs[vel][0])*(b-vs[vel][0]);} for(i=1;k131;i++){ if(v[i][1]!=0)vs[i][1]=sqrt(vs[i][1]/v[i][1]); vs[i][0]=vs[i][0]*fcal+foff; vs[i][1j=vs[i][1]*fcal; a=i*velcal+veloff; if(v[i][1]!=0)fprinff(fpout,"%f %f %f °/0i\n",a,vs[i][0],vs[i][1],v[i][1]);) prinff("processing complete\n");}  Time Averaging Program  #include <stdio.h> #include <math.h> #include <stdlib.h> float vavg,favg,fcal, foff, velcal, veloff; int vel, fr, sz, flag; int i, dcount,pcount, ocount,size; char fn[30]; main(){ FILE *fpin, *fpout, *fpcal; clrscr(); printf("\n\n^TAVG : TIME AVERAGEING OF FORCE DATA\n\n\n"); prinff("Loading Calibraiton data\n"); if((fpcal=fopen("C:\\TC\\CALDAT ","r"))==NULL){prinff("cannot open calibration file\n");exit(1);} fscanf(fpcal,"%f %f %f %f",&fcal,&foff,&velcal,&veloff); fclose(fpcal); prinff("\nInput data file name =>"); scanf("%s",fn); if((fpin=fopen(fn,"r"))—NULL){prinff("cannot open input file\n");exit(1);} prinff("\nInput sorted file name =>"); scanf("%s",fn); if((fpout=fopen(fn,"w"))==NULL){printf("cannot open sorted file\n");exit(1);) fscanf(fpin,"%i",&size); prinff("\n\nThe data field contains %i points\n",size); prinff("\nHow many data points per average =>"); scanf("°/01",&sz);  84 dcount=0; ocount=0; do{ i=0; do{ if(flag==0){fscanf(fpin,"%i %i",&fr,&vel); dcount++;} flag=0; i++; if(i> 1)(if(abs(vel-vavg/(i-1))<=4)( vavg+=vel; favg+=fr;} else {flag=1; i--;}) else { vavg=vel ; favg = fr;} )while(flag==0 && i< sz && dcount < size); printf("."); ocount++; vavg=vavg/rvelcal+veloff; favg=favg/Ncal+foff; fprintf(fpout,"%f %f °/01\n",vavg,favg,i); }while(dcount < size); prinff("\n\aTotal number of points generated = %i\n\n",ocount); fclose(fpin); fclose(fpout);}  Data Cleaning Program  #include <stdio.h> char ans[30]; int i,j, a[5], point1 , point2; float b[3]; main() { FILE *fpin, *fpout; clrscr(); prinff("\n\n^CLEAN : REMOVING BAD DATA POINTS FROM DATA FILES\n\n"); prinff("Output file name =>"); scanf("%s",ans); if((fpout=fopen(ans,"a+t"))==NULL)(prinff("Cannot open Output file\n");exit(1);} 1=1 ;point1=1 ; do{ printf("\nlnput File #%i Name =>",i); scanf("%s",ans); iffflpin=fopen(ans,"r"))==NULL)(printf("Cannot open Input File #%i\n",i); exit(1);} do{ rewind(fpin); printf("\nStart Point =>"); scanf("%i",&point1); printf("\nEnd Point =>"); scanf("/oi",&point2); printf("^ \n\n"); if(point1>0)( for(j=0;j<point1;j++)  85 fscanf(fpin,"%i^%f^%i^%i^%i °01^%I %f\n",&a[0],&b[0],&a[1 ],&a[2],&a[3],&a[4],&b[1 ],&b[2]); for(j=pointl ;j<=point2;j++){ fscanf(fpin,"%i^%f^%i^0/0 i^%I^%i^%f ,&a[0],&b[0],&a[1],&a[2],&a[3],&a[4],&b[1],&b[2]); fprintf(fpout,"%i^%f^°/0i^%i^Oki^°/0i^%f ,a[0],b[0],a[1],a[2],a[3],a[4],b[1],b[2]);  0/0f  %f\n" %f\n"  }while(pointl >0); i++; fclose(fpin); }while(point1>-1);}  Force Removal, and Regression Program  #include <stdio.h> #include <math.h> #include <stdlib.h> float vavg,favg,fcal, foff, velcal, veloff, r, k; float v2sum, fsum; int vel, fr, sz, flag, regcount; int i, dcount,pcount, ocount,size; char fn[30]; main(){ FILE *fpin, *fpout, *fpcal, *fpoffset ; cIrscr(); prinff("\n\nTAVGRM : TIME AVERAGEING OF FORCE DATA, REMOVING NON AERO FORCES\n\n\n"); prinff("Loading Calibraiton data from: c:\\project\\progs\\cal.dat\n "); if((fpcal=fopen("C:\\project\\progs\\cal.dat ","r"))==NULL)(printf("cannot^open^calibration file\n");exit(1);} fscanf(fpcal,"%f %f %f %f",&fcal,&foff,&velcal,&veloff); fclose(fpcal); prinff("\nInput data file name =>"); scanf("%s",fn); if((fpin=fopen(fn,"r"))==NULL)(printf("cannot open input file\n");exit(1);} printf("\nlnput sorted file name =>"); scanf("%s",fn); if((fpout=fopen(fn,"w"))==NULL)fprintf("cannot open sorted file\n");exit(1);} fscanf(fpin,"%i",&size); if((fpoffset=fopen("C:\\project\\progs\\offset.dat ","r"))==NULL){prinff("cannot^open^offset file\n");exit(1);} prinr\nLoading Offset data from : c:\\project\\progs\\offset.dat\n "); fscanf(fpoffset,"%f %f",&r,&k); printf("\nAverage Rolling Resistance = %f\n",r); prinff("Average Brake and Internal Viscous Drag = %f\n",k); printf("\nThe data field contains %i points, it is averaged over 250 point segments\n\n",size); sz=250;  86 dcount=0; ocount=0; regcount=0; do{ i=0; do{ if(flag==0){fscanf(fpin,"°/0i %i",&fr,&vel); dcount++;} flag=0; i++; if(i> 1)(if(abs(vel-vavg/(i-1))<=4){ vavg+=vel; favg+=fr;} else {flag=1; i--;}} else { vavg=vel ; favg = fr;} )while(flag==0 && i< sz && dcount < size); printf(" (%3i)",i); ocount++; vavg=vavg/i*velcal+veloff; favg=(favg/ilcal+foff)-r-vavg*k/3.6; if(i>100){fprintf(fpout,"%f^°/0i\n",vavg,favg,i); fsum+=favg; v2sum+=vavg*vavg/12.96; regcount++; prinff("x");} else printf(" "); if(ocount/1 0==ocount/1 .0)printf(" \ n"); }while(dcount < size); prinff("\n\aTotal number of points generated = %i\n\n",ocount); printf("The gradient m = %7.5f \n",fsum/v2sum); printf("The number of points used = ^\n",regcount); fclose(fpin); fclose(fpout);}  Time Averaging of Fuel Data Program  #include <stdio.h> #include <math.h> #include <stdlib.h> float vavg,favg,fcal, Toff, velcal, veloff, r, k; float fsum,fc; int vel, fr, sz, flag, regcount; int i, dcount,pcount, ocount,size; char fn[30j; main(){ FILE *fpin, *fpout, *fpcal; cIrscr(); printf("\n\nTAVGRMF : TIME AVERAGEING OF FUEL CONSUMPTION DATA\n\n\n"); printf ^Calibraiton data from: c:\\project\progs\\cal.dat\n "); if((fpcal=fopen("C:\\project\\progs\\cal.dat ","r"))==NULL){printf("cannot^open^calibration file\n");exit(1);} fscanf(fpcal,"%f %f %f cYof",&fcal,&foff,&velcal,&veloff); fclose(fpcal); printf("\nlnput data file name =>"); scanf("%s",fn); if((fpin=fopen(fn,"r"))==NULL){printf("cannot open input file\n");exit(1);} printf("\nlnput sorted file name =>");  87 scanf("%s",fn); if((fpout=fopen(fn ,"w"))==N ULL){printf("cannot open sorted file\n");exit(1);) fscanf(fpin,"%i",&size); printf("\nThe data field contains %i points, it is averged over 250 point segments\n\n",size); sz=250; dcount=0; ocount=0; regcount=0; do{ i=0; do{ if(flag==0){fscanf(fpin,"%i %i",&fr,&vel); dcount++;} flag=0; i++; if(i> 1 ){if(abs(vel-vavg/(i- 1 ))<=4){ vavg+=vel; favg+=fr;} else {flag=l; i--;}} else { vavg=vel ; favg = fr;} }while(flag==0 && i< sz && dcount < size); ocount++; vavg=vavg/i*velcal+veloff ;favg=f avg/i; fc=vavg/(3.6*favg); if(i>100){fprintf(fpout,"%15.3f %15.3f %15.3f %4i\n",vavg,favg,fc,i); printf("%15.3f %15.3f %15.3f %4i\n",vavg,favg,fc,i); regcount++;} }while(dcount < size); printf("\n\aTotal number of points generated = %i\n\n",ocount); printf("The number of points used = %i \n",regcount); fclose(fpin); fclose(fpout) ;}  88  APPENDIX B : FORCE REGRESSION PLOTS The plots presented in this appendix are identified in the following manner. The letter refers to this appendix, and the digit to the configuration tested. The test numbers are indicated on the diagram.  0.12  Test 2  0.100.08C)  2 U-  0.06 0.04 0.02  -  -  .........  0.00  0  41p  -  20^40^60^80^1 00  120  Velocity [km/hr] Figure B-1 Regression analysis of the force data for the modified truck with extended roof (baseline or reference case).  )  ! i  0.12 Test 4  + .  0.10-  7  0.080)  2 0.06u_  0.040.02  .........  0.00  0  40^do^80^100  120  Velocity [km/hr] Figure B-1 Regression analysis of the force data for the modified truck with extended roof (baseline or reference case).  0.12 Test 5 +  0.104.  0.08-  •'  .0.  0)  2 0.06 U-  it,--  -  +  -- ' - -  .....  0.04-  .... " ...  + .. ' '^°IN ...." .... -  +  +  0.02 0.00  -  0  irJ^4o^do^io^100  120  Velocity [km/hr]  Figure B-1 Regression analysis of the force data for the modified truck with extended roof (baseline or reference case).  0.12 Test 7 4s  0.100.0840  2 0.06 u-  -  40  0.04-  40 4,^-  0.02  4s  ses  sis  -  ----------  0.00  0  20^40^60^80^100  ^  120  Velocity [km/h r] Figure B-1 Regression analysis of the force data for the modified truck with extended roof (baseline or reference case).  0.12 Test 8 40  0.100.08  -  „  0)  2 0.06 u_  is  -  0.04  is .-' Ali  .-- 4:  -  .-'  .•".  -  is .---.-  0.02  3. - ' — - - 4'  -  ...  0.00  0  — 414•  20^40^60^80^lOo  120  Velocity [km/hr] Figure B-1 Regression analysis of the force data for the modified truck with extended roof (baseline or reference case).  0.12 Test 9 al•  0.10-  45  0.08-  41  0)  2 U-  0.06NIN  0.04 0.02  -  -  ----------  0.00  0  20^40^60^80^160  120  Velocity [km/hr] Figure B-1 Regression analysis of the force data for the modified truck with extended roof (baseline or reference case).  C  Figure B-1 Regression analysis of the force data for the modified truck with extended roof (baseline or reference case).  ■  12% Test 11  10%40  80/041  0)  2 6%  sis  LL  sis  40/0-  .• .."'  4s 4s^  2%-  4s  -16 ----------  0%  0  20^40^60^80^1 00 Velocity [km/hr]  120  Figure B-1 Regression analysis of the force data for the modified truck with extended roof (baseline or reference case).  0.12 Test 12  0.10-  4•  0.08zC) U-  0.06  41  -  0.040.02  -  -----------  0.00  0  4;^41  40^60^80^1 00  120  Velocity [km/hr] Figure B-1 Regression analysis of the force data for the modified truck with extended roof (baseline or reference case). ^  1-L  0  +  12% Test 2 40  10%4.  0) U-  6°/040  4%  2% 00/0  •  • -  ----------  0  4o^do^  80^1 00  Velocity [km/hr]  Figure B-2 Regression analysis of the force data with the horizontal fence .  ^  120  12%  Test 3  10%.4  80/00)  U-  6°/04P/0  2%  -  -  -------^4,  ..^....  0^20^40^60^80^100  Velocity [km/hr] Figure B-2 Regression analysis of the force data with the horizontal fence,  ^  120  {^,  12%  Test 4  10%40  8%2 60/0u_  4s  4%2%  sls  40 -  ----------  0%  4s  0  -  0^4o^do^80^1 00  Velocity [km/hr] Figure B-2 Regression analysis of the force data with the horizontal fence.  120  C  12% Test 6^  4s  10%-  +  80/0-  ../  41  0) 2 6croa_  ^,  40/0  --'  „FP  ...--  -  AP --^4s ....  ...-".  . Ale ^+  2%  ...-  ^----------  0°/0  0  ^— "Si. sis  — 44^  irJ^4o^do^80^1 00 Velocity [km/hr]  Figure B-2 Regression analysis of the force data with the horizontal fence.  ^  120  12% Test 7  10%-  40  80/0-  40/02% 00/0  +  -  0  4o^do^1 00 Velocity [km/hr]  Figure B-2 Regression analysis of the force data with the horizontal fence.  120  12% Test 8  10%  40  —  8°/0  +  atr/0— 2%  AIL -  —  ----------  0°/0  0  20^40^60^80^100  Velocity [km/h r] Figure B-2 Regression analysis of the force data with the horizontal fence,  120  12%  Test 1 i•  10%-  u_  80/0-  cm 2 6%419''  t. ....."4,,  4°/0-  .'•'  .•'  4'  +  2%  -  ---------- . IC - - 41 -  0°/0  0  0^40^60^80^100  120  Velocity [km/hr] Figure B-3 Analysis of the force data obtained with one horizontal and two vertical fences installed on the cube-truck during the road tests .  <  12% Test 2  10%80/0-  4°/02%  0°/0  -  ----------^------  0  20^40^60^80^lOo  120  Velocity [km/hr] Figure B-3 Analysis of the force data obtained with one horizontal and two vertical fences installed on the cube-truck during the road tests .  12% Test 3  10%80/0.52) da EM-  "Pr !I• 41  4.  4c)/0-  2%  .........  00/0  0  -4F-  ......  20^40^60^80^100  120  Velocity [km/hr]  Figure B-3 Analysis of the force data obtained with one horizontal and two vertical fences installed on the cube-truck during the road tests  0 t C4  12% Test 4  10%80/0C)  2 6%u.. 4°/0 --"  2% ---------  0%  0  40  -  20^40^60^80^1 00  Velocity [km/hr] Figure B-3 Analysis of the force data obtained with one horizontal and two vertical fences installed on the cube-truck during the road tests.  120  113  APPENDIX C : FUEL CONSUMPTION PLOTS  e 1 <-  V'  e(4  8^ Test 7  7  -  t  6  010  40  -  o 5-  U, 40 4•  40 40  E 4-  40 40  40  0  = u_  321  40  -  20^Lib^do^80  100  ^  Velocity [km/hr] Figure C-1Fuel consumption data for the reference (baseline) configuration.  120  ^ ^  8^ Test 8  7  -  6c o 5  40  -  40  E n 4o 3am 2)  1  -  0^  0  20^40^60^80^100  Velocity [km/h r]  Figure C-1Fuel consumption data for the reference (baseline) configuration  120  ..! i 7 (  8^  Test 9  t ki  uc=) u_  E  *  +  •  •1 •  40 +  ++  4it  o 3-  il•  0  CD D  21  IN  +  +  -  0^  0^  Lio^60^do^100 Velocity [km/hr]  Figure C-1Fuel consumption data for the reference (baseline) configuration ,  120  vC  8^ Test 10  7  -  6c o 5-  40  E 4m  o 32U-  1  -  10 20 30 40 50 60 70 80 90 100 110  Velocity [km/h r] Figure C-1Fuel consumption data for the reference (baseline) configuration  8^ 7-  Test 11  E 641  o 50. E m 4-  40^4, 40  --  40  410  o 3-  =: 2-  4 1)  u_  40  1o  o  20^40^60^80^160  Velocity [km/hr]  Figure C-1Fuel consumption data for the reference (baseline) configuration.  120  t  8^ Test 12  7  -  64s  o5  -  4s  E D  4-  (/)  0  40 sls  3-  sis ses  41 40  a) 2LL 1  sis sis  -  0^20^40^60^80^100  ^  Velocity [km/hr] Figure C-1Fuel consumption data for the reference (baseline) configuration ,  120  ^ ^  8^ Test 1  7  -  6 c  0  -  5  sis  -  4P  4E = o3 (1)  •  4s  -  21  40  11.  -  0^  0  4o^do^Eio^100 Velocity [km/hr]  Figure C-2 Fuel consumption data with horizontal fence .  120  ^  ^8^ Test 2  7  -  _.E 6c 0 5E m 4co c  0 30  • * 4.  lls sles^IN + +  4*  al• +  is  0 = 2-  +  ii.  40 4.  10^  0  4o^60^60^100  Velocity [km/hr] Figure C-2 Fuel consumption data with horizontal fence .  120  fr\-44-  8^ Test 3  7  E  -  6-  05•  (I)  o 3  45  -  o n 2-  U-  IN  1  -  0^  0  4o^do^go^100 Velocity [km/h r] Figure C-2 Fuel consumption data with horizontal fence .  120  8^ Test 4  7  -  6o 5E 4_  o  3-  a=  2-  )  • 40  43  1*  LL  10^  0^20^4o^do^go^100  Velocity [km/hr]  Figure C-2 Fuel consumption data with horizontal fence .  120  ,4`  8^ Test 5  7  -  E 6-  41 40  o 54=  0_ E 4-  43  4,  el•  NIN  0  3-  a= 2-  sio  )  U-  1  45  -  0^  0^2 0^40^60^80^160 Velocity [km/hr] Figure C-2 Fuel consumption data with horizontal fence .  120  8^ Test 6  7  -  42  t 6 0o 5 la  42  il•  -  .  42  42 42 42  42^  -  4E m w c  o3 U L 2u_ 1  41  4.  42  42^  42  42  4.  42 *  42  42  -  =  (  42  )  42  -  0^2 0^40^60^80^100  Velocity [km/h r] Figure C-2 Fuel consumption data with horizontal fence .  120  8  le 0Ca "  7  Test 7  -  40  6-  NIN  +  o 5-  E m 4-  Uo 32u_ 1 w c  4.  4.  slo  4. +  +  +  4•  mD  4.  (  •  -  o  o^40^60^go Velocity [km/hr] Figure C-2 Fuel consumption data with horizontal fence .  100  ^  120  1  8 Test 8  7  -  6-  42  c 0 5  -  E 4D 0 3  •••  4.  ele  -  co n 2-  LL  els  -  o  o  20^40^60^80^100  Velocity [km/hr]  Figure C-2 Fuel consumption data with horizontal fence,  ^  120  d  8 Test 1  7-  E 60 5-  40 45^ 40  4.  4  E 4=  4.  el•  o 375 = 2-  10^ 0  20^40^do^80^100 Velocity [km/hr]  120  Figure C-3 Fuel consumption as affected by the truck speed in the presence of one horizontal and two vertical fences  8^ 7 C  Test 2 -  6-  c 05-  E  4-  4,  *  *  + +  4.  IN  4.^I.  el• 4. 4.  (I)  c o 30 clm 2U1  + +  )  -  o  o  20^40^60^80^1 00 Velocity [km/h r]  120  Figure C-3 Fuel consumption as affected by the truck speed in the presence of one horizontal and two vertical fences.  c,  8^ Test 3  7  -  6sis^  ses^ 4s ses^sis 40^ sis  c 05-  4s  40  E  =  4s  4-  40 sis  4s  C')  o 3  4s  -  is  2CD m  sis  4s  1  -  o  o  20^40^60^80^100  120  Velocity [km/hr] Figure C-3 Fuel consumption as affected by the truck speed in the presence of one horizontal and two vertical fences .  ^  8^ Test 4  7  -  E 6o5  -  E n  ele le^  4-  cn o 3  -  Alm  4, ^41  u 40  a) 2-  IL.  1  -  ^0^  0  20^40^60^80^160  120  Velocity [km/hr] Figure C-3 Fuel consumption as affected by the truck speed in the presence of one horizontal and two vertical fences .  

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