dugksFoam: An open source OpenFOAM solver for the Boltzmann model equation

A deterministic Boltzmann model equation solver called dugksFoam has been developed in the framework of the open source CFD toolbox OpenFOAM. The solver adopts the discrete unified gas kinetic scheme (Guo et al., Phys. Rev. E, 91, 033313 (2015) ) with the Shakhov collision model. It has been validated by simulating several test cases covering different flow regimes including the one-dimensional shock tube problem, a two-dimensional thermal induced flow, and the three-dimensional lid-driven cavity flow. The solver features a parallel computing ability based on the velocity space decomposition, which is different from the physical space decomposition based approach provided by the OpenFOAM framework. The two decomposition approaches have been compared in both two and three-dimensional cases. The parallel performance improves significantly using the newly implemented approach. A speed up by two orders of magnitudes has been observed using 256 cores on a small cluster.