Gerris is a Free Software program for the solution of the partial differential equations describing fluid flow. The source code is available free of charge under the Free Software GPL license.
A brief summary of its main features:
Solves the time-dependent incompressible variable-density Euler, Stokes or Navier-Stokes equations
Solves the linear and non-linear shallow-water equations
Adaptive mesh refinement: the resolution is adapted dynamically to the features of the flow
Entirely automatic mesh generation in complex geometries
Second-order in space and time
Unlimited number of advected/diffused passive tracers
Flexible specification of additional source terms
Portable parallel support using the MPI library, dynamic load-balancing, parallel offline visualisation
Volume of Fluid advection scheme for interfacial flows
Accurate surface tension model
Multiphase electrohydrodynamics
the get a copy of the software visit : http://gerris.dalembert.upmc.fr/