Applications of dynamic hybrid grid method for three-dimensional moving/deforming boundary problems

摘要

In the previous work, the authors had developed a dynamic hybrid grid generation method and an unsteady flow solver for two-dimensional incompressible and compressible unsteady flows with moving or morphing boundary. In this paper, the dynamic hybrid grid generation method and the unsteady flow solver are extended to three-dimensional complex geometries with moving and/or deforming boundaries, and coupled with force and moment calculation, and the integration of the rigid body, six degrees-of-freedom (6DOF) equations of motion. In order to enhance the flexibility and efficiency of moving grid generation, the dynamic hybrid grid method combines the 'Delaunay graph' mapping approach, node relaxation based on 'spring' analogy and local re-meshing strategy. Firstly, the prism/tetrahedral/Cartesian hybrid grids are adopted to discrete the initial computational domain over complex configurations. Once the bodies move or deform, the grid points in the boundary layer of the moving/morphing bodies are moved firstly with a modified advancing-layer method, the grid points in the outer far-field keep stationary, while the grid points between the last layer of body-fitted grids and the internal boundary of the specified far-field are mapped by the 'Delaunay graph' mapping method. But the background grids (the Delaunay graph) themselves are deformed by the simple node relaxation based on 'spring' analogy to improve the efficiency. Then the quality of the deformed grids is checked with some criteria. If the deformed grids do not pass the checking step, a local re-meshing procedure is carried out. Based on the dynamic hybrid grids, a parallel implicit finite-volume flow solver for 3D unsteady Navier-Stokes equations is developed also. In order to deal with the problems of multi-body separation, the integration of the rigid body, 6DOF equations of motion is coupled in the same framework of the flow solver. The applications for complex 3D morphing configurations demonstrate the robustness and efficiency of present method.