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.

Parallel NetCDF

PnetCDF is a library providing high-performance parallel I/O while still maintaining file-format compatibility with  Unidata's NetCDF, specificallythe formats of CDF-1, 2, and 5. 


SU2 is an open-source collection of software tools written in C++ and Python for the analysis of partial differential equations (PDEs) and PDE-constrained optimization problems on unstructured meshes with state-of-the-art numerical methods.  This makes it an open source solution for computational fluid dynamics.


UCNS3D is a Computational Fluid Dynamics (CFD) solver developed primarily at Cranfield University in the United Kingdom.


WARP3D is under continuing development as a research and production quality code for the solution of large-scale, 3-D solid models subjected to static and dynamic loads.


XBeach is a two-dimensional model for wave propagation, long waves and mean flow, sediment transport and morphological changes of the nearshore area, beaches, dunes and backbarrier during storms.