The Overlapping Grid Technology And Its Applications In Complex Flowfield Of Projectiles

With the rapid development of Computational Fluid Dynamics (CFD) method, numerical simulation plays more and more important roles in engineering applications. But computing the flow fields about three-dimensional complex configurations accurately becomes a difficult task, if it is attempted to generate body fitted patching grids with proper clustering. The overlapping grid method simplifies the construction of computational grids about complex geometries by subdividing the physical domain into regions which can accommodate easily generated grids. Therefore the overlapping grid technology is of important application value. In this thesis, a reliable dynamic overlapping structured grid technology is studied and a computing software is developed to predict the flow field of projectiles with complex configurations. The following works had been performed:First of all, the numerical methods which are used in this thesis are studied. The governing equations, which are the thin-layer approximations to the three-dimensional time-dependent compressible Navier-Stokes equations, are solved using the finite volume method in spatial discretization and upwind flux-difference-splitting technique of Roe in convective terms discretization. An implicit approximate factorization method is used to advance in time. In the simulation of turbulence flows, Spalart-Allmaras one-eqution turbulence model is implemented to evaluate the turbulent viscosity and the convergence rate at which many problems are solved can be accelerated with the use of multigrid.Secondly, the method of overlapping structured grids is investigated. The method mainly includes overlapping grid generation, hole boundary definition, intergrid communication, composite grids for multigrid method, overlapped region, global accuracy and solution algorithm modifications.Then, the feasibility of the overlapping grid algorithm above is validated. The overlapping grid method was applied to a number of numerical test cases (NACA 0012 airfoil, Multielement airfoil, Onera M-6 wing and plate transverse jets), in order to prove the dependability of this algorithm.Finally, by the applications of the overlapping algorithm above in simulation of the flow field of lateral jet interaction for a projectile-like wing-body configuration, the characteristics of this flow field were shown and the interaction effects on aerodynamics were studied. Numerical test results indicate that the overlapping grid technology developed in this thesis achieves some actual engineering application value.