A simple, entropy-based dissipation trigger for SPH

Understand

Smoothed Particle Hydrodynamics (SPH) schemes need to be enhanced by dissipation mechanisms to handle shocks.

• Most SPH formulations rely on artificial viscosity and while this is working well in pure shocks, attention has to be payed to avoid dissipation where it is not wanted.
• Commonly used approaches include limiters and time-dependent dissipation parameters.
• The former try to distinguish shocks from other types of flows that do not require dissipation while in the latter approach the dissipation parameters are steered by some source term ("trigger") and, if not triggered, they decay to a pre-described floor value.