Gerris is an Open Source Free Software library for the solution of partial
differential equations describing fluid flow. Gerris is supported by NIWA
(National Institute of Water and Atmospheric research) and by the
Marsden Fund of the Royal Society of New Zealand. The code is written
entirely in C and uses both the GLib Library and the GTS Library for
geometrical functions and object-oriented programming.

WWW: http://gfs.sourceforge.net/