# Minimal (Density-Energy) SPH¶

This scheme is a textbook implementation of Density-Energy SPH, and can be used as a pedagogical example. It also implements a Monaghan AV scheme with a Balsara switch, like the GADGET-2 scheme. It uses very similar equations, but differs in implementation details; namely it tracks the internal energy (u) as the thermodynamic variable, rather than entropy (A). To use the minimal scheme, use

./configure --with-hydro="minimal"


As it uses a very simple, fixed artificial viscosity, only the SPH:viscosity_alpha parameter has any effect for this scheme. This will change the strength of the artificial viscosity throughout the simulation, and has a default of 0.8.