SPH Applications

Introduction

Smoothed Particle Hydrodynamics (SPH) was developed to study non-axisymmetric phenomena in astrophysics. However, developments based on this approach have been launched for a far wider range of applications by various research teams in association with industry. Since the meshfree technique facilitates the simulation of highly distorted fluids/bodies, it offers great potential in fields such as free-surface flows, elasticity and fracture, where Eulerian methods can be difficult to apply. Furthermore, with the ever increasing size and cost reduction of computer clusters, parallel implementations allow large-scale simulations that were previously limited to mainframes.

Sphere impacting the free-surface of water

In this work, an analysis based on a three-dimensional parallelized SPH model developed by ECN and applied to free surface impact simulations is presented. The aim of this work is to show that SPH simulations can be performed on huge computer as EPFL IBM Blue Gene/L with 8’192 cores.

This paper presents improvements concerning namely the memory consumption, which remains quite subtle because of the variable-H scheme constraints. These improvements have made possible the simulation of test cases involving hundreds of millions particles computed by using more than thousand cores. This is illustrated by a water entry problem, namely on a test case involving a sphere impacting the free surface at high velocity. In the first part, a scalability study using from 124’517 particles to 124’105’571 particles is realized. In the second part, a complete simulation of a sphere impacting the free surface of water is done with 1’235’279 particles.

A convergence study is achieved on pressure signals recorded by probes located on the sphere surface. Furthermore, ParaView-meshless developed by CSCS, is used to show the pressure field and the effect of impact.

The academic case of a billard ball impacting the water free surface described by Laverty is used for smoothing length analysis, scalability performances and local flow analysis. Figures represent the numerical domain with 2 sub-domains: a rigid body, the billard ball, and a half spherical tank of water.

Geometric and Flow conditions:

  
Tank of Water
Diameter 6 m
Water Density 1’000 kg.m-3
llard Ball
Diameter 2 m
Ball Density 1 kg.m-3
Impact velocity 6 m.s-1
Flow Properties
Reynolds Number 1.18 107
Froude Number 1.354