Open Flower: is an open source CFD software (FLOW solvER, literally) written in C++. It is mainly devoted to the resolution of the turbulent unsteady incompressible Navier-Stokes equations. http://openflower.sourceforge.net/index2.html
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. http://gfs.sourceforge.net/wiki/index.php/Main_Page
Dolfyn: An initiative in Noord-Brabant, a Dutch province in the south of the Netherlands, particularly in the region around Eindhoven. The goal of dolfyn is to promote, introduce and teach the use of modern numerical simulation techniques in general and the use of Computational Fluid Dynamics (CFD) in particular. http://www.dolfyn.net/dolfyn/index_en.html
SPHysics: A Smoothed Particle Hydrodynamics (SPH) code inspired by the formulation of Monaghan (1992) developed jointly by researchers at the Johns Hopkins University (U.S.A.), the University of Vigo (Spain), the University of Manchester (U.K.) and the University of Rome La Sapienza (Italy). http://wiki.manchester.ac.uk/sphysics/index.php/Main_Page
OpenFVM : A general CFD solver released under the GPL license. It was developed to simulate the flow in complex 3D geometries. Therefore, the mesh can be unstructured and contain control volumes with arbitrary shape. The code uses the finite volume method to evaluate the partial differential equations. As well as solving the velocity and pressure fields, the code is capable of solving non-isothermal multiphase flow. http://openfvm.sourceforge.net/
CAD/Meshing tools
Salome: A multipltform software that has a CAD module and can be use with Code Saturne and Code_Aster. It also has a post processing module. http://www.salome-platform.org/
GMSH: a three-dimensional finite element mesh generator with built-in pre- and post-processing facilities. http://www.geuz.org/gmsh/
NETGEN is an automatic 3d tetrahedral mesh generator. It accepts input from constructive solid geometry (CSG) or boundary representation (BRep) from STL file format. The connection to a geometry kernel allows the handling of IGES and STEP files. NETGEN contains modules for mesh optimization and hierarchical mesh refinement. Netgen is open source based on the LGPL license. It is available for Unix/Linux and Windows. http://www.hpfem.jku.at/netgen/
Tetgen: Meshing tool, generates the Delaunay tetrahedralization, Voronoi diagram, constrained Delaunay tetrahedralizations and quality tetrahedral meshes. The main goal of TetGen is to generate suitable meshes for solving partial differential equations by finite element or finite volume methods. http://tetgen.berlios.de/
Post Processing software
Paraview: is an open-source, multi-platform data analysis and visualization application. http://www.paraview.org/
Calculix: A Free Software Three-Dimensional Structural Finite Element Program. http://www.calculix.de/
Octave: A high-level language, primarily intended for numerical computations. It provides a convenient command line interface for solving linear and nonlinear problems numerically, and for performing other numerical experiments using a language that is mostly compatible with Matlab. It may also be used as a batch-oriented language. http://www.gnu.org/software/octave/
Scilab: A scientific software package for numerical computations providing a powerful open computing environment for engineering and scientific applications. http://www.scilab.org/platform/