Overset Adaptive Cartesian/Prism Grid Method for Stationary and Moving-Boundary Flow Problems

摘要

In the present study, an overset adaptive Cartesian/prism grid method was developed to simulate moving-boundary flow problems. The method combines the advantage of an adaptive Cartesian/prism grid in geometry flexibility with that of the Chimera approach in tackling moving-boundary flow without grid remeshing. Advantages of the method include: 1) Cartesian cells are more efficient in filling space given a certain length scale than triangular/tetrahedral cells. 2) Searching operations can be performed very efficiently with the octree data structure 3) Solution-based and geometry-based grid adaptations are straightforward to carry out. Human interference for moving-boundary flow simulation was reduced to a minimal level. This is mainly due to the automation of the hole-cutting and the donor-cell-identification procedures. The preceding procedures used the ADT and the octree data structured for carrying out the search operations in an efficient manner. An implicit LU-SGS approach is employed for the time integration. This allows the user to specify the time step based on geometric bounds rather than stability limits. A significant reduction in the number of hole-cutting operations is attained. Hence the overhead created by the grid-generation procedures is reduced to less than 10%. The grid generator and flow solver were coupled successfully to tackle a moving-boundary flow problem with reasonable computational results. Future research includes the flowing areas: 1) enabling solution-based grid adaptation and 2) enabling nonrigid body deformations.