Verification and validation studies of OpenFOAM for transonic compressible flow simulations inside high voltage circuit breaker diffusers

Accurate compressible flow simulations are known to improve the prediction quality of breakdown voltages in various test duties of high voltage circuit breakers. In this paper, we systematically investigate the solver quality of the open source CFD code OpenFOAM in handling transonic flow phenomena that typically occur inside the breaking chamber of high voltage circuit breakers, during contact separation. The solver quality is then compared with that of chosen commercial CFD tools. The main advantage of OpenFOAM is that, contrary to most of the commercial simulation tools, it is license fee free and allows access to the source code. This means that complicated multi-physics phenomena inside the arcing chamber can be directly modelled into the code by users, which opens an opportunity to remove limitations of commercial CFD tools. This paper consists of a number of verification and validation studies. Particularly, the shock capturing capability of OpenFOAM will be evaluated for the transonic internal flow which typically occurs in high voltage circuit breakers. The solver quality of OpenFOAM will then be compared with a number of benchmark commercial CFD tools. Overall, Open-FOAM shows acceptable shock capturing capabilities in the performed verification and validation studies, with the solver quality comparable to some of the tested commercial CFD tools. There is still room for further solver quality improvements in OpenFOAM by implementing better shock capturing schemes such as a density-based flux-difference-splitting scheme or by writing better physical modelling of the shock/boundary layer interaction into the open architecture of OpenFOAM. Considering the unlimited extensibility of the open architecture and the already proven CFD solver quality, a large part of the high voltage circuit breaker development activities can be benefited by introducing an OpenFOAM-based simulation technology.