Coolfluid 3 is a scientific software framework designed for the implementation of simulation techniques related to fluid dynamics, supporting multi-physics simulations. It was developed as an evolution from COOLFluiD 2, a code primarily developed at the Von Karman Institute for fluid dynamics (VKI). Coolfluid 3 is a major redesign, taking into account lessons learned from the previous developments, and the new code is being developed as a free software (under LGPL v3 license), with all developments happening in public on the github community site.