Cavitation Simulation on Conventional and Highly-Skewed Propellers in the Behind Condition

The cavitating flows around conventional and highly-skewed propellers in the behind-hull condition are simulated by an in-house RANS solver, EllipSys (Sørensen 2003), with the cavitation model, based on the homogeneous equilibrium modeling (HEM) approach and a vapor transport equation. The validation of the cavitation model in EllipSys has been conducted for the cavitating flows on 2D/3D hydrofoils (Shin 2010). Prior to the cavitation simulation, the open-water characteristics of the propellers from the computation are compared with those from the propulsion test for the fully-wetted flows (Li & Lundström 2002, Lindell 2005). The cavitation simulation is performed for the flow condition corresponding to that in the cavitation tunnel test for the ship model equipped with the propeller (Johannsen 2004, Lindell 2005). Instead of modeling the hull for the behind-hull condition, the measured wake field in the propeller plane is applied by using a non-homogenously loaded actuator disk (Mikkelsen et al 2007) placed in a plane upstream of the propeller. The variation of the computed cavitation profile with respect to the blade angle is compared with that from the cavitation tunnel test. The present work describes the study of implementing a HEM cavitation model for computing unsteady cavitation patterns in behind-hull condition with respect to blade angles and cavity extent on the complicated geometry of a conventional/highly-skewed propeller. In the computations, the efficiency of the non-homogeneously loaded actuator disk as behind-hull wake field for the propeller inflow is demonstrated successfully. The computed unsteady cavitation patterns in behind-hull condition and with respect to the blade angle has qualitatively acceptable accuracy, but with respect to the cavity extent, there are quantitative discrepancies.