Research Of The Generation Of Dynamic Unstructured Meshes

Numerical simulation of unsteady flow problems involving moving boundaries has already become a hot spot of the Computational Fluid Dynamics(CFD) in the world, and the generation of dynamic grid is an essential technology about it. This thesis unifies the project of the National Natural Science Fund "The Computational Method and Grid Generation involving Moving Boundaries", and studies the generation and application of the 2-D unstructured grids and the 2-D dynamic unstructured meshes. The main contents are as follows:Generate the 2-D unstructured grids using the advancing front method (AFM). Several techniques are used in this method such as the structured background grids, initial front division and nodal smoothing techniques. Then it gives some examples about 2-D unstructured grids in this thesis. The results indicate that the mesh quality is satisfied and the meshes can be used in the numerical calculations.Three kinds of technologies about dynamic unstructured meshes are studied, they respectively are: spring analogy method, elasticity approach and local remeshing method, and it gives emphasis to the elasticity approach in this thesis. In this method, the mesh is modeled as an elastic body and the motion of the nodes is governed by the equations of elasticity, then solve the equations by a finite element method and the displacement of the nodes can be calculated. Several examples about the 2-D dynamic unstructured meshes are given in this thesis and each method is compared with their good and bad points. The results show that the elasticity approach has the stronger capability of the mesh deformation than the spring analogy method, but the efficiency is lower. The local remeshing method suits in the problems where the mesh deformation is large, but the efficiency is low.Two typical examples of 2-D unstructured grids involving moving boundaries are calculated, and the results are good. This indicates that the spring analogy method and the elasticity approach can be applied in the numerical simulations.