Mesh-Free Contamination Transport Modelingusing CAD Geometries

We propose to develop a simulation code capable of performing contamination transport analyses using complex geometries with moving components without needing a surface mesh of the utilized geometry. Meshing is a time consuming process that can easily account for over 50% of the total effort involved in completing the analysis. It requires modifying the CAD model to delete small parts such as drill holes to avoid an excessively fine mesh which increases simulation run time while at the same time reducing the quality of results due to an increased numerical noise arising from fewer particles striking the small triangles. The code will utilize the existing open source CAD library OpenCASCADE to directly operate on STEP files. The CAD library will be used to load the geometry and to replace the line-triangle intersection checks used for testing surface impact in particle tracing codes with a line-CAD check. This approach retains the analytical description of the surface geometry preventing feature loss due to tessellation. It also simplifies introducing dynamic behavior since the CAD components can be transformed or translated through parametric equations. Objective of the Phase I effort is to complete the feasibility study by developing a standalone code that can simulate motion of particles around a CAD-defined geometry. We also investigate schemes for storing surface data using options such as point clouds or face splitting. Timing of this direct method will be compared to the legacy approach based on a triangular surface mesh. We also investigate approaches for utilizing surface charge to compute the spatial variation of electric fields to simulate charged particle transport which may arise when analyzing lunar regolith or electrostatic return. This study will naturally lead to a Phase II effort during which the developed algorithms will be further developed into an end-user contamination analysis code.