Three-dimensional Hybrid Grid Generation And The N-s Equations To Solve

In this thesis, a strategy for generating three-dimensional unstructured viscous grids is investigated and a flow field solver by solving three-dimensional Navier-Stokes (N-S) equations on hybrid grids is developed. The viscous flow around M6 wing and F4 wing-body configuration are simulated and compared with the results of wind tunnel experiment.In order to solve N-S equations, a strategy is presented for generating three-dimensional unstructured viscous grids automatically, which using the advancing-layers method (ALM) for generating prism or hexahedral grids in viscous dominated flow regions and using the advancing-front method (AFM) for generating conventional tetrahedral grids in the other field of computational region. In this process, the stretched function is used to make grids smooth and gradual.As the flow field solver is developed for hybrid grids, which solving N-S equations on unstructured grids, the Baldwin-Lomax (B-L) turbulent model is adopted on unstructured grids. In this paper, the upwind scheme and the central scheme are presented for solving 3-D N-S equations using the cell-center finite volume spatial discretization and four-stage Runge-Kutta time stepping scheme, with standard convergence acceleration techniques such as local time stepping and implicit residual smoothing.Taking M6 wing and F4 wing-body configuration as computational examples, some results by solving Euler and N-S equations are presented. Compared with the results of wind tunnel experiment, the results of N-S solver are much better than those of Euler solver, and the upwind scheme is better than the central scheme in catching shock wave.