A Numerical and Experimental Investigation of Wall-Pressure Fluctuations Induced by Sheet Cavitation Instabilities on Lifting Surface

The paper is based on some previous works of the authors aimed to study the phenomenology of cavitation instabilities. In the present work, a particular attention is paid to the analysis of spatio-temporal wall-pressure fluctuations in the context of fluid structure coupling investigations. The work is based on a numerical and experimental study, whose objective was to analyze the wall-pressure fluctuations beneath an unsteady partial cavitating flow developing on an hydrofoil. Experiments were carried in a water tunnel, on a partially cavitating hydrofoil based on extended multi-point wall pressure measurements together with flow visualizations. 2D Navier-Stokes simulations solves the RANS equations combined with a physical model of cavitation The two-phase flow mixture is considered as a homogeneous medium for which the ratio of liquid and vapor is controlled by a barotropic state law. The numerical resolution is based on the SIMPLE algorithm, modified to take into account the high compressibility of the liquid/vapor mixture. The results show that various dynamics are caught by the model in agreement with the experiments. Two main unstable dynamics were observed leading to a strong variation of surface loading. The paper provides quantitative data about the severe unsteady loading that is experienced by the structure, which should very useful in a fully problem of Fluid Structure Interaction. The possibility of a structural response of the foil to the unsteady loading and how it could promote the cavitating flow instability is also discussed.