A study on mesh refinement in OpenFOAM for wave propagation problems in fluid power systems

Abstract

Due to rising importance of wave propagation effects in fluid power systems, CFD (computational fluid dynamics) codes take also on greater significance. These highly sophisticated codes have the capability to calculate the full resolution of a pressure field as well as of a velocity field in arbitrarily complex geometries. But this brilliant development brings also a huge disadvantage, namely enormous computational costs. Because of this reason CFD software often disqualifies itself as first choice application. However, considering a whole computational domain and it's physics the idea comes up, that there are regions which require a higher spatial resolution than others. Mesh refinement is a common practice to get a higher resolution in regions of greater interest while reducing the overall number of cells and hence the simulation time. This paper presents results of simulations with OpenFOAM, where mesh refinement has been done with polyhedral elements. As a simple benchmark system a pipe with a cross-sectional jump has been used. First the optimal CFD result for this system has been determined by doubeling the number of elements in each direction for each additional simulation until the variations in the outcome has vanished. This simuation result has been compared to a set of simulations, where mesh refinement has only adapted to the region after the cross-sectional jump, where the higher number of cells has been considered as a benefit.