Research On The Arithmetic And Research Of Finite Volume Based On Overset Unstructured Grid

The unstructured overset grid algorithm is explored in this paper. The simplicity and automation in the inter-grid-boundary definition are realized using the"wall distance"as a basic parameter. The neighbor-to-neighbor jump search algorithm is efficiently utilized to find the donor cell. And this search is efficient because the search path is one dimensional even in the 3-dimensional grid system. The width of the inter-grid boundary is about one or two cells. In fluid field solving, the numerical flux is estimated using high-accuracy Roe scheme with limiter. In time marching, we use dual-time stepping together with implicit LU-SGS scheme and get reasonable results efficiently.The difference of the fluid computation between single grid and overset grids lies in the dispose of the computation boundary. In overset grids, there are not only physical boundary but also inter-grid boundary. Each grid block is solved independently and the communication between the grids is realized through the area interpolation. By this means, we can get the global fluid variables.In order to verify the accuracy, credence and effectiveness of the unstructured overset grid algorithm, steady and unsteady flow field of NACA0012 airfoil are simulated. The unsteady flow field is caused by the oscillation of the airfoil. The two computational results are both compatible well with the experimental data. We also compute NACA0012 airfoil and certain three-foil flow field separately with explicit 4-step Runge-Kutta scheme and the implicit LU-SGS scheme and results show the latter is much more efficient. In the end, the capability of the algorithm to deal with multi-bodies in relative movements is demonstrated by a dropping drank problem. It turns out that the unstructured overset grid is valuable and promising in practical application.