A switch to reduce SPH viscosity

Smoothed particle hydrodynamics is a Lagrangian particle method for fluid dynamics which simulates shocks by using an artificial viscosity. Unlike Eulerian methods it is not convenient to reduce the effects of viscosity by means of switches based on spatial gradients. In this paper we introduce the idea of time-varying coefficients which fits more naturally with a particle formulation. Each particle has a viscosity parameter which evolves according to a simple source and decay equation. The source causes the parameter to grow when the particle enters a shock and the decay term causes it to decay to a small Value beyond the shock. Tests on one-dimensional shocks and a two-dimensional shock-bubble interaction confirm that the method gives good results. (C) 1997 Academic Press.