Study Of Flow Field Simulation And Mesh Technique Involving Moving Boubdaries Structures

Flow field simulation is one of the key issues in the flow movement study. Fluid-Solid Interaction (FSI) is an interdiscipline branch dealing with Hydromechanics and Solid mechanics, which is powerful to study the interaction between the flow domain and solid domain. Here numerical methods using dynamic unstructured meshes for solving flow problems involving moving boundaries are implemented.Mesh movement strategy is implemented by using the modified spring analogy. The proposed mesh update technique is developed to avoid the generation of squashed invalid elements and maintain mesh quality by considering each element shape and grid scale to the definition of the spring stiffness. The method is applied to several 2D and 3D boundary correction problems for fully unstructured meshes and evaluated by a mesh quality indicator. With these applications, it is demonstrated that the present method can not only prevent invalid element occurred but also preserve mesh quality near the moving boundaries even under large motions of bodies.Finite element large eddy simulation is developed to simulate the flow field. A stabilized finite element technique, actualized by streamline upwind Petrov-Galerkin (SUPG) stabilized method and three-step finite element method, for large eddy simulation (LES) is developed to predict turbulent flow with high Reynolds number which can be applied in structural wind engineering. Weak form of LES motion equation is combined with the SUPG stabilized term for the spatial finite element discretization, and explicit three-step scheme is implemented for the temporal discretization where the pressure is computed from Poisson equation deduced from the incompressible condition. Results show that the present method can effectively suppress the instabilities of the calculating fields and well predict the unsteady flow.Then, the discrete finite element method for static grid is extended to moving mesh and a discrete finite element method based on moving mesh is set up. An explicit three-step SUPG stabilized finite element large-eddy simulation program is combined with the mesh update stratagy through the Arbitrary Lagrangian-Eulerian (ALE) technique. Flow field around structures under a variety of boundary movement cases are simulated.