Prediction of tip vortex cavitation inception with low-order panel method

Tip vortex cavitation is the first type of cavitation to take place in most cases. Because it always produces radiated noise, avoiding or at least delaying tip vortex cavitation is crucial for achieving low radiated noise emissions. The present study aims to predict the tip vortex cavitation inception with the low-order panel method, which is widely used at the early propeller design stage. First, a velocity smoothing parameter varying with the age of vortex is adopted to align the wake. This leads to a wake shape that coincides very well with the wake pattern from a RANS solver. A consistent formula for evaluating the smoothing parameter for different cases is also achieved with the fitting method. Second, the tip vortex circulation is calculated based on the converged wake shape and doublet distribution. This procedure is found to be independent from the panel size. Finally, based on the minimum pressure distribution along the tip vortex, cavitation inception numbers are obtained for the Potsdam Propeller Test Case (PPTC) and the propeller 4383 developed in NSRDC. The results show a good agreement with the experimental measurements.