Forced Moving Boundary Numerical Method Using Smoothed Particle Hydrodynamics

The solid-driven moving boundary is common in Fluid Machinery, and also an important area of research. Different from the definition of the free surface, the interface of two-phase flow and the liquid diffusion boundary, the solid-driven moving boundary is defined as the forced moving boundary. As a Lagrangian form of meshfree particle method, Smooth Particle Hydrodynamics (SPH) method is mesh-free, adaptive, Lagrangian with particle nature, and is very suited to deal with fluid flow problems.SPH method was applied to the numerical simulation of the solid-driven moving boundary problem, and the studies found that the traditional Lennard-Jones boundary force model is strongly non-linear and easily leads to inconvergence. Therefore, a linear boundary force model was utilized to study the impact on the stability of the SPH numerical simulation.The spring-damping boundary force model was constructed, which has better long-term stability. It not only can guarantee the boundary force to be a linear relationship with the distance, but also associates the boundary force with the velocity. By successfully applying the model to solid-driven moving boundary flow problem, a feasible method is provided for the boundary treatment of the SPH method.This thesis analyzed how the SPH method is applied to the moving boundary flow problem, and introduced the SPH program written in FORTRAN language. Lennard-Jones and spring-damping model were applied respectively as boundary treatment, and constant smoothing length and variable smoothing length were also applied respectively. Three moving boundary models, which are from translation to rotation, were simulated in a gradual way. At last, the feasibility and long-term stability of the spring-damping model were validated.With the numerical simulations of the three typical examples, we concluded that: Compared with the Lennard-Jones boundary force model, the spring-damping model is long-term stable and is better to deal with the solid-driven moving boundary flow problem; The comparisons with the results of the Fluent indicated the correctness of the boundary treatment; In addition, the studies found that the variable smoothing length can improve the accuracy of the SPH method.