Initial Conditions

Tools for the creation of initial conditions are available via the WoMa and SEAGen open-source python packages, including: creating spherical or spinning planetary (or similar) profiles; placing particles to match arbitrary profiles with precise SPH densities; and setting the initial target and impactor positions and velocities, as presented in Kegerreis et al. (2019) and Ruiz-Bonilla et al. (2020).

They are available with documentation and examples at and, or can be installed directly with pip (,

Settling initial conditions with fixed entropies

If the particles’ equations of state include specific entropies, and the initial conditions file includes specific entropies for each particle (in PartType0/Entropies), then configuring SWIFT with --enable-planetary-fixed-entropy will override the internal energy of each particle each step such that its specific entropy remains constant.

This should be used with caution, but may be a convenient way to maintain an entropy profile while initial conditions settle to equilibrium with their slightly different SPH densities.