Development of reverse meshing technology on geometry reconstruction for CFD code GASFLOW-MPI

Nuclear Power Plants (NPPs) containment study is an important part of nuclear safety analysis. With the aim of predicting the performance of hydrogen in the NPPs containment during severe accident, CFD codes are always applied as the analysis tools. With the development of computational capability, the researchers from both the academic side and industrial side try to re-study the existing simulation cases by using the refined mesh, as way to resolve more detailed information. During the pre-processing stage of CFD study, CAD is the necessary part providing geometric information on meshing. With recent development, CFD codes like GASFLOW-MPI can directly generate high resolution Cartesian mesh from CAD. However, there are still many experimental benchmarks and engineering applications where only paper-based blueprints are available for geometric information. Concerning the fact that no CAD models exist, lots of hand-based calculation and measurement need to be done by CFD analysts on geometry modeling. When some certain re-studies of the old simulation cases needed, the same work may have to be repeated multiple times, owing to the need of re-meshing in different sizes or local refinements. Therefore, a solution for reconstructing CAD from the mesh in the old simulation data is vital to improving the efficiency of CFD analysis. In this work, the reverse meshing technology with two kinds of smoothing processes, the Marching Cubes smoothing approach and Laplacian smoothing approach, are developed for CFD code GASFLOW-MPI to reconstruct the CAD geometry from the previous simulation data, which free engineers from the tedious and repetitive work on geometry construction. Three application cases are used to evaluate the performance of the two reverse meshing technologies. The results show that both reverse meshing technologies could recover the CAD geometry from Cartesian mesh of GASFLOW-MPI. Moreover, the Laplacian smoothing could fit the general surface in much smoother degree.