Investigation of cloud cavitating flow in a venturi using adaptive mesh refinement

Unsteady cloud cavitating flow is detrimental to the efficiency of hydraulic machinery like pumps and propellers due to the resulting side-effects of vibration, noise and erosion damage. Modelling such a unsteady and highly turbulent flow remains a challenging issue. In this paper, cloud cavitating flow in a venturi is calculated using the detached eddy simulation (DES) model combined with the Merkle model. The adaptive mesh refinement (AMR) method is employed to speed up the calculation and investigate the mechanisms for vortex development in the venturi. The results indicate the velocity gradients and the generalized fluid element strongly influence the formation of vortices throughout a cavitation cycle. In addition, the cavitation-turbulence coupling is investigated on the local scale by comparing with high-fidelity experimental data and using profile stations. While the AMR calculation is able to predict well the time-averaged velocities and turbulence-related aspects near the throat, it displays discrepancies further downstream owing to a coarser grid refinement downstream and under-performs compared to a traditional grid simulation. Additionally, the AMR calculation is unable to reproduce the cavity width as observed in the experiments. Therefore, while AMR promises to speed the process significantly by refining the grid only in regions of interest, it is comparatively in line with a traditional calculation for cavitating flows. Thus this study intends to provide a reference to employing the AMR as a tool to speed up calculations and be able to simulate turbulence-cavitation interactions accurately.