[http://www.comsol.com/ COMSOL Multiphysics] (formerly FEMLAB) is a finite element analysis software package that includes predefined partial differential equations for many fields of physics.
Notes for COMSOL users
COMSOL has a library of the properties of common materials, but if you want to use it, you must start COMSOL in SI units mode. If you try to use the materials library in another units mode, it will use the numerical values of the properties without converting them, and give you wrong answers. For example, the density of concrete is about 2300 kg/m3. If you start COMSOL in FPS (Foot Pound Second) mode, it will use 2300 as the density of concrete in lb/ft3, which is much too high.
See also Software Tools.