Evaluations of the outcome variability of RANS simulations for marine propellers due to tunable parameters of cavitation models

Abstract

There are two issues with cavitation modeling that need to be resolved: (1) the lack of sound physical meaning for the Vapor Volume Fraction (VVF) to set a threshold a priori for determining the range of cavitation extension; (2) the outcome variability (uncertainty) on the model's predictability resulting from the uncertainties of the model's tunable parameters, whose exact values are usually hard to obtain. This paper uses as a tool the methodology of the Cavitation Occurrence Probability (COP), which can be regarded as the resolution of the first issue, to resolve the second issue and evaluate the outcome variability due to the tunable parameters of three popular cavitation models, i.e. the Full Cavitation Model (FCM), Zwart-Gerber-Belamri (Z-G-B) and Schnerr-Sauer (S-S) models. PANS simulations were performed for a cavitating propeller flow with these three cavitation models, whose tunable parameters were varied to generate the VVF distributions and thrust data for comparisons with the experimental data. The results show that the FCM model is capable of yielding the most accurate predictions of cavitation at its default setting and thrust at some other setting, while the S-S model is capable of yielding the most precise (certain) predictions of cavitation and thrust.