The Virgo Consortium

The Hydra Code

Hydra gas particles

The formation of large-scale sturcture in the dark matter distribution.


Hydra is an N-body hydrodynamics code which uses a combination of Adaptive PPPM for the gravity and Smoothed Particle Hydrodynamics for the gas forces.

The code evolves a mixture of purely gravitational and gas particles. It begins with a box containing a large number of uniformly distributed particles whose positions and velocities are perturbed in a physically motivate manner and then the motion of every particle is followed through time.

The animation shows the formation of large-scale sturcture in the dark matter distribution, from redshift z=20 to the present time. The movie is centered on a forming rich cluster of galaxies.


The initial paper for “The Hydra code” has been published as Couchman et al. 1995. For more information please contact Hugh Couchman.