Surface Characteristics Modeling And Interaction Phenomena Simulation Of Incompressible SPH Fluids

Fluid animation has been widely applied in special effects for 3D movies and games,virtual reality,visualization,military simulation and many other fields in recent years.Nowadays people pursue high realistic,complex phenomena and real-time interactive fluid simulation results which brings great challenges to computer graphics and animation fields.In order to deal with requirements such as high resolution,large amount of calculation and real-time simulation,traditional animation techniques can not meet the increasing demands while physically-based fluid simulation technology becomes the main and feasible solution.As one of the most hot research direction,Smooth Particle Hydrodynamics(SPH)based fluid simulation with advantages like mass conservation,suitable for great deformation,easy to handle free surface,solid boundary and capture spray,foam,has attracted attention of more and more researchers.This paper focuses on the issues of surface features,surface construction,multiphase flow,fluid-solid coupling for incompressible fluid,using Navier-Stokes(N-S)equations as the basic model of fluid dynamics and employing SPH as the main numerical solution.The research of fluid simulation in this paper is composed of four aspects:surface tension and adhesion,surface reconstruction,interaction of fluid and fluid,interaction of fluid and solid.The main work and contributions in this paper are summarized as follows.1)In order to capture more stable and realistic microscopic features of fluid surface,a surface tension and adhesion method based on implicit incompressible SPH is presented in this paper which can solve the problem of not considering adhesion and not steady and fast of tension model.Molecular cohesion and surface area minimization is considered for surface tension,and adhesion is added to better show the microscopic characteristics of surface.To simulate surface tension and adhesion stably and efficiently,the forces model is integrated to implicit incompressible SPH method.The experimental results show that the method can better simulate surface features in a variety of scenarios meanwhile ensures stability and efficiency.2)The surface constructed by traditional color field method is rough and uneven,and using anisotropic kernel is time-consuming,so a efficient surface reconstruction approach employing anisotropic kernel is addressed in this paper.It simplifies the structure of anisotropic kernel and only uses particles near the surface to construct fluid surface.It is demonstrated that this approach can guarantee the smoothness of surface and obtain a good speedup comparing to original anisotropic kernel method.3)Due to density estimation of fluid particles are problematic in interfaces,number density is adopted to correct fluid density in this paper.Then the density is used for deducing other physical quantities and setting up multiphase flow model.In addition,for the interfaces problems such as gaps and overlaps of surface construction in multiphase fluid simulation,a surface construction scheme for multiphase interfaces is proposed in this paper.It modifies the equation of anisotropic kernel function and employs a "binary tree" strategy for surface construction.The achieved results illustrate that the method can realistically simulate the interaction phenomena between different fluids without cracks and overlaps in multiphase interfaces.4)In order to handle fluid-solid boundary issue in a unified particle framework,an improved sampling and relaxation approach of solid surface is presented.It samples solid into boundary particles which are directly interacting with fluid particles.The fluid-solid coupling approach based on individual time-stepping is proposed by combining particle-based fluid-solid interaction method with individual time-stepping algorithm.The experimental results reveal that this approach can efficiently realize two-way interaction of fluid and solid with good realistic effects.