CalculiX is a finite element based package designed to solve field problems.
Code_Saturne is a public domain CFD code.
Delft3D is a world leading 3D modeling suite to investigate hydrodynamics, sediment transport and morphology and water quality for fluvial, estuarine and coastal environments.
FEniCS is a popular open-source (LGPLv3) computing platform for solving partial differential equations (PDEs).
Hyperworks is a GUI for Pre/Post processing for engineering applications.
The INS2D code solves the incompressible Navier-Stokes equations in two-dimensional generalized coordinates for both steady-state and time varying flow.
The INS3D code solves the incompressible Naiver-Stokes equations in three-dimensional generalized coordinates for both steady-state and time varying flow.
OpenFOAM is started as a C++ library for building CFD solver applications and utilities. Now some of the documentation describes it as a free, open source CFD software package.