Research And Application Of Unstructured Grid Adaptive Technology

Computational Fluid Dynamics(CFD) plays a more and more important role influid basic researches and aircraft design processes. High precision and highresolution of CFD is needed for elaborate design. There are two common mehods toimprove computation precision: using high order numerical schemes or using refinedcomputation grid. The aim of the thesis is to establish an effective grid adaptationmethod based on unstructured mixed grid, which can be used for complex flow fieldcomputation, to improve the resolution of shock or vortex. Effective shapeparameterization and responsive grid deformation are two basis of CFD shapeoptimization. FFD (FreeForm Deformation) which can parameterize the shape anddeform the grid at the same time, is suit for shape optimization. The computationprecision and resolution can be improved after the work, and FFD can be used forshape optimization.In the preface, the background and significance of local-refined grid adaptationand FFD technique is introduced. The main contents of this thesis are then presented.In the2nd chapter, the numerical methods are introduced. The local gridadaptation technique based on unstructured mixed grid includes five aspects: theconstruction of detectors, the strategy of grid cell subdivision, the method of handlingprism cells, the projection of suface grids, grid optimization and flow fieldinterpolation method. The usual proceedings, algrithoms used, and the gridsensitivity to design parameters of FFD are also included.In the3rd chapter, standard numerical cases are performed to verify the feasibilityand efficiency of the grid adaptation technique. In shock adaptation, the cases includetwo dimensional flow over NACA0012airfoil, three dimensional subsonic flow overM6wing and supersonic flow over a sphere. In vortex adaptation, the case is flowover the delta-wing configuration at large angle of attack. The cases used to verifyFFD technique are structured and unstructured grids of M6wing.In the4th chapter, the adaptation technique is applied to simulation of flow overAmerican military fighter F16, where shock and vortex are presented respectively.The numerical result shows that the adaptation method is capable of handlingcomplex configuration problems where shock and vortex are presented in the flowfield.Finally, a brief conclusion is given. The shortage of the thesis and areas needingadditional research and development are presented.