A computational and experimental study of viscous flow around cavitating propulsors

A method for analyzing viscous flow around partially-cavitating and super-cavitating hydrofoils is presented. A nonlinear perturbation potential-based panel method is used to first solve the cavity solution in inviscid flow. A boundary layer solver is then applied on the surface bounded by the union of the foil and cavity surface. The effects of viscosity on lift and drag are studied for both partial and super-cavitating hydrofoils. Viscosity is shown to have a substantial effect in the condition of partial cavitation: on the other hand, minimal deviations from the inviscid solution are observed in the case of super-cavitation. Finally, the applicability of the present method to analyzing the viscous flow around cavitating propulsors is discussed. Experiments are performed at the MIT Variable Pressure Water Tunnel to ultimately assess the validity of coupled inviscid/viscous cavity analysis method. Velocities are measured along a rectangular control surface surrounding the hydrofoil, in the boundary layer region, as well as in the proximity of the cavity surface. The cavitation number is evaluated by measuring the pressure inside the cavity via a manometer. The measurements are compared to the numerical results from the coupled, nonlinear, inviscid cavity analysis method and a boundary layer solver. Forces are computed from measured velocities via momentum integrations and are compared with those predicted by the numerical method.