Research On Fluid Movement And Solid-fluid Coupling Simulation Based On SPH

With the development of performance of computer hardware, a explosive growth of applications such as virtual reality,3D games, medical training has happened in re-cent years. At the same time, computer animation technology which is the foundation of these application, has made great progress. Fluid,as the most widespread form of matter, attracts many researchers’ attention comparing with other research objects in computer animation. In addition, the fluid in the real world are often coupling with the surrounding environment. Especially, there are some cases that the coupling effect mainly drives the movement of fluid(such as fluid flow in porous media, interaction be-tween hair and water,and so on).There fore, this paper focused on the simulation of fluid movement and solid-fluid coupling which are proved to be significant to the theoretical research and practical applications.Because of the computational complexity of fluid simulation, the traditional grid based methods are inadequate in dealing with those applications which emphasize real-time performance and interactivity. In order to meet the requirements of real-time and interactive simulation, this paper started from the N-S equation in Lagrangian view-point, and studied several issues in basic simulation of fluid movement such as the discretization of N-S equation and its numerical solution, neighbor particles seraching methods and the visualization of fluid, basing on the SPH which is a non-grid method. Then, the coupling of solid and fluid was deeply studied. At last, following results have been achieved:(1) By studying the mechanism the movement of fluid and appling SPH method in simulating fluid, a basic framework of Lagrangian fluid simulation was obtained. After the analysis of several key issues affecting the simulation accuracy and performance, an efficient explicit time integration schema which updating the velocity and position of fluid has been proposed, which effectively reduced the computational cost without losing accurancy. Moreover, this paper studied the reconstruction of particles based fluid surface, and extracted the isosurface of density field based on the Marching Cubes algorithm.(2) For the solid-liquid coupling, a unified particle model for the interaction of solid and fluid has been proposed, and it avoided the particles stacking and particles sticking aroud the boundaries. The particle representation of solid was obtained by uniform particles sampling on the surface based on a sign distance field. Moreover, the solid particles was used in the correction of fluid densiy to get a lower particle density fluctuation rate(0.5%～3%), and sign distance field was also applying to correct the position of particles which might penetrate the solid boundaries.(3) This paper also studied the simulation of fluid surface tension, and focused on the IIF model which can causes non-physical particle clustering when dealing with large deformation flow and the irregular shape of fluid surface. In this paper, surface tension is modeled by an attraction-repulsion force which formalized by a Lennard-Jones like potential function, and a SPH tension correction term which based on the normal difference between neighboring particles is introduced to minimize the surface area and smooth the surface. Experimental results show that the proposed method can simulate the surface tension effect accurately and stably.