Numerical Investigation on the Effect of Blade Loading on Unsteady Sheet Cavitation Patterns

Cavitation commonly manifests itself as vapour structures attached to the suction surfaces of impeller, runner or propeller blades. The numerical study carried out here seeks to correlate the changes in the behaviour of sheet cavitation to variations in blade geometry. The analysis is run for a two-dimensional stationary cascade. The streamwise loading distribution is the metric used to characterise the geometry. It determines the rate and amount of work generated across the channel and is directly connected to blade surface pressure. In this study, the test sample consists of a set of varying blade profiles characterised by specific loading configurations: foreloaded, aft-loaded or bespoke distributions. Time-resolved simulations of the cavitating flow are generated to study cavity behaviour. Computations are run through Fluent using the SST URANS formulation. The Zwart-Gerber-Belamri homogeneous cavitation model is used to treat cavitation. A range of behaviours are observed for the cavitation patterns. Variations are found in inception conditions, shape and sheet stability. For the latter, two dynamic regimes are identified with a transition point that varies according to the loading profile. A pair of tradeoff relations are also observed: hydrodynamic efficiency versus suction performance and suction performance versus cavity stability. The results demonstrate the capacity of the loading distribution to affect cavitation dynamics.