Planetary Hydro Scheme

This scheme is based on Minimal (Density-Energy) SPH but also allows multiple materials, meaning that different SPH particles can be assigned different equations of state (EoS). Every SPH particle then requires and carries the additional MaterialID flag from the initial conditions file. This flag indicates the particle’s material and which EoS it should use.

The Balsara viscosity switch is used by default, but can be disabled by compiling SWIFT with make CFLAGS=-DPLANETARY_SPH_NO_BALSARA.

Note: to access the boundary-improvement method presented in Ruiz-Bonilla+2022, use the planetary_imbalance_RB22 git branch and compile with --with-hydro=planetary-gdf. However, we instead recommend using the REMIX SPH scheme, as it has effectively replaced this method.

REMIX SPH

REMIX is an SPH scheme designed to alleviate effects that typically suppress mixing and instability growth at density discontinuities in SPH simulations (Sandnes et al. 2025), and also includes the multiple EoS options as the base Planetary scheme. For more information on what is included in the REMIX scheme and how to configure SWIFT to use REMIX, see: REMIX SPH.