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CFD codes list
A large list of commercial, public-domain and shareware Computational Fluid Dynamics codes.
http://icemcfd.com/cfd/CFD_codes.html
N-Body/Particle Simulation Methods
An extensive online tutorial with examples and code references.
http://www.amara.com/papers/nbody.html
ORSA - Orbit Reconstruction, Simulation and Analysis
ORSA is a C++ framework for the development of algorithms and programs oriented to the simulation and analysis of the orbital evolution of bodies in space.
http://orsa.sourceforge.net