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UBC Theses and Dissertations

Numerical modelling of the Abrasive Waterjet (AWJ) cutting process using Smoothed Particle Hydrodynamics (SPH) method Budaraju, Siddharth


Computational fluid dynamics (CFD) is a valuable tool for the design or analysis of engineering processes in various industries. One such process is waterjet cutting, in which a high-pressure water jet mixed with abrasive is used to cut various materials. Alluvial garnet is an excellent abrasive, allowing cuts of 2 inches thickness or more, but due to its high cost, research into new, low-cost abrasives are needed. Metallurgical slag, a byproduct from smelting operations is found to be a promising abrasive alternative for waterjet cutting. However, slag has quite different material properties, particle size distributions, and flow characteristics than alluvial garnet, which can enhance or degrade the cut quality of the cut piece and/or experimental setup. A fundamental understanding of how the abrasive properties affect both the formation of the high-pressure jet and the material removal process is required. The main objective of the thesis is to develop a computational model of the waterjet cutting process that can provide an optimized parametric setup helping in better experiments. Challenges involved in modelling this problem constitute understanding flow characteristics such as the jet formation in the nozzle, multiphase (water and abrasive), compressibility, severe material distortions and deformations, which makes it very difficult to use mesh-based methods, such as finite element or finite volume. These complications can potentially be addressed through a mesh-free approach. Smoothed particle hydrodynamics (SPH) method, a Lagrangian-based meshless particle approach, approximates the differential terms as discrete summations based on kernel functions accounting for the weighted average influence of neighboring particles in the flow. Owing to the flexibility of its meshless formulation and generic applicability to various types of governing equations, SPH can be used to model the high-pressure jet, multiphase liquid/abrasive flow, and material removal process within a single unified modelling environment. This thesis will present the motivation, objectives and proposed methodology of the research, and will present a preliminary evaluation of the SPH methodology. An open-source SPH code, Python-based SPH code called PySPH, will also be discussed with an assessment of its accuracy and efficiency for compressible liquid flows, liquid/abrasive multiphase flows, and material removal processes.

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