Lagrangian particle-based simulation of fluid-solid coupling on graphics processing units

Abstract

SUMMARYLagrangian particle method has been widely used in computer physics and graphics; however, numerically solving the partial differential physical equation on a great number of particles is a computationally complex task. In this paper, a unified particle method on graphics processing units is proposed to simulate fluid-solid interaction with large density ratio interactively. Motivated by microscopic molecular dynamics, we consider the solid object as a particular fluid limited to solid motions; therefore, fluid-solid interaction as well as solid-solid interaction could be solved directly using multiphase weakly compressible smoothed particle hydrodynamics solvers. And then, we present a momentum-conserving particle collision handling scheme to prevent fluid penetrating into solid objects. In the simulation, a measure of particle densities is used to handle density discontinuities at fluid-solid interfaces, and consequently, new formulations for density-weighted inter-particle pressure and viscous forces are derived. Moreover, to realistically simulate various small-scale interaction phenomena such as water droplets flowing on solids' surfaces, a surface tension model that uses density-weighted color gradient and can obtain a stable and accurate surface curvature is employed to capture the interfacial fluid-solid tensions. Because all of the computation is carried out on graphics processing unit and no CPU processing is needed, the proposed algorithm can exploit the massive computational power of graphics processing unit for interactive simulation with a higher particle resolution. The experiment results show that our method can simulate realistic fluid-solid couplings at interactive frame-rates even for up to 126 k particles.

Particle Merging-and-Splitting

“…Similar force-based formulations are also used in solidfluid coupling [21] by directly applying forces between nearby particles [22], [23] or introducing additional pressure force [24], [25]. The simplicity of the force formulation allows coupling Eulerian fluid simulations with particlebased solid simulations [26] and particle-based fluid simulations with deformable solids [27]- [29] and, using continuous collision detection, sheet-based cloth simulations [30], [31].…”

“…An alternative solution would be to modify the intersecting particle positions at the end of each time-step to ensure that the previously merged particles no longer intersect. However, while this is a commonly-used technique in computer graphics [23], [29], position corrections often inject extra energy into the system that impacts the stability of the simulations or introduces artificial vibrations. Moreover, this seemingly minor energy injection of position correction can lead to catastrophic events with fracture simulations, instantly shattering all bonds and causing entire objects to explode into individual particles.…”

“…We compare our merging-and-splitting method with forcebased approaches, using penalty [6], [8] or SPH-based [22], [23] force formulations, and impulse-based collision handling methods [39]- [43]. cloth from two different heights.…”

Design of a touch sensation application including surface tension sample using a haptic device in engineering education

“…In liquids, each molecule is attracted to other molecules by an equal cohesive force from each side . Thus, all forces acting on a molecule in the interior are balanced (Figure ).…”