The Numerical Investigation Of The Problems Related To Moving Boundary Based On DF/FD And LES/FD Method

In the thesis, we have reviewed the development and applications of the Fictitious Domain (FD) method and the Large Eddy Simulation (LES). The Direct-forcing-based Fictitious Domain method has been described in detail, which has been incorporated into LES method. We have employed the method of LES /fictitious domain on the fixed and uniform Cartesian grids and used a discreteδ-function to transfer explicitly quantities between the Eulerian and Largrangian nodes, so that the quantities on the inner solid and the boundary of fluid-solid can be solved better. In order to improve the efficiency, the half-staggered finite difference scheme for the fluid flow sub-problem and Fast Fourier Transform algorithm for Poisson equation have been used in our methods.We have mainly employed the Fictitious Domain method and LES method to investigate the problems related to the moving boundary. The migration of the neutrally buoyant spherical particles in circular Poiseuille flow has been simulated at moderately high Reynolds numbers for the first time. The behaviors of the single- and multi- particles migrating to equilibrium positions have been investigated at different Reynolds numbers, different ratios of the radius of the particle to the radius of the tube and different volume factions. Our results agree with the experiments' observations which have not been numerically examined previously. In addition, we also have studied the structure of the vortex in the wake of the fixed spherical particle for different Reynolds numbers. They have proved that our methods perform reliably and accurately.