OpenFOAM - OpenFOAM® - Official home of The Open Source Computational Fluid Dynamics (CFD) Toolbox.
AQUASIM - In order to support environmental scientists in finding an «adequate» model of the system...
ANSYS Fluent - ANSYS engineering simulation and 3D design software delivers product modeling solutions with unmatched scalability and a comprehensive multiphysics foundation.
STOAT - STOAT - a dynamic sewage treatment works modelling package
MATLAB - A high-level language and interactive environment for numerical computation, visualization, and programming
Wolfram Mathematica - Mathematica has characterized the cutting edge in specialized processing—and gave the chief calculation environment to a large number of pioneers, instructors, understudies, and others around the globe.