Computational fluid dynamics prediction of marine propeller cavitation including solution verification

This paper analyses the effect of grid refinement on computational fluid dynamics simulations of cavitating propeller flow. Refinement is made both globally, using geometrically similar grids, and locally, by applying adaptive grid refinement. The test case is the E779A propeller operating in uniform inflow conditions in a cavitation tunnel. This allows more computationally efficient steady simulations to be made, permitting a grid uncertainty analysis not previously seen for cavitating flow computations. Unsteady simulations are also presented in order to compare two turbulence modelling approaches. Differences in the discretisation uncertainty in terms of propeller thrust and torque were found to be small between wetted and cavitating flow conditions, although the order of convergence for the cavitating case is lower. Overall the largest effect of grid refinement is found to be in the tip vortex region, where differences in the predicted cavity extents are significant between grids. The use of adaptive grid refinement allows improved capture of tip vortex cavitation with fewer total grid cells, although the cavity extent is limited by increasing eddy viscosity when using RANS. Application of DDES reduces this influence somewhat, motivating further study into the potential of scale-resolving simulations in combination with adaptive grid refinement for vortex cavitation prediction.