Dynamic Hybrid Grids for Unsteady 3-D Large Movement Simulation

The most difficult part of the solution process for the flowing problems between t1uid and structure interaction is the generation of an appropriate grid. Dynamic hybrid grids are applied to mesh the flow out a body moving with large displacement. A prism layer mesh near the no-slip surfaces or moving boundary is created to capture the boundary layers, a hexahedral mesh for far field meshing by advancing front method, between them are tetrahedral elements generated by Octree-based meshing algorithm and smoothing by Delaunay triangulation method. With the motion of moving body, the prismatic grids move with the body, while the hexahedron grid remains stationary. Meanwhile, the tetrahedral grids are deformed according to the motion of solid body with a ‘spring' analogy approach. In order to avoid the crossing between the tetrahedral grids with the hexahedron grids or the negative volume as displacement becoming large, the tetrahedral grids are regenerated with a several times from beginning to end. Then the flow solution is interpolated from the old into the new. App1ication this grid method to simulate a small new designed pump-propelled AUV turning around in horizontal plane from stationary. The turning radius is compared with analytic solutions and experimental data and agreed well