Deformable Overset Grid for Unsteady Aerodynamic Simulation

A deformable overset grid method was proposed to simulate the unsteady aerodynamic problems with multiple flexible moving bodies. This method uses an unstructured overset grid locally coupled with mesh deformation to achieve both robustness and efficiency. The overset grid hierarchically organizes the sub-grids into CLUSTERs and LAYERs, allowing for overlapping/ embedding of different type meshes, of which the mesh quality and resolution can be independently controlled. At each time step, mesh deformation is locally applied to the sub-grids associated with deforming bodies by an improved Delaunay graph mapping method which uses a very coarse mesh as the background graph. The graph is moved and deformed by a spring analogy according the specified motion and then the computational meshes are relocated by a simple one-to-one mapping. An efficient implicit hole-cutting and inter-grid boundary definition procedure is fully automatically implemented for both cell-centered and cell-vertex schemes based on wall distance and an alternative digital tree (ADT) data search algorithm. This method was successfully applied to several complex multi-body unsteady aerodynamic simulations and the results demonstrated the robustness and efficiency of the proposed method for complex unsteady flow problems, particularly for those perform large relative motion and self-deformation simultaneously.