Scale effects on hull pressure fluctuations due to cavitating propellers

In this paper we describe several scale effects that may occur on cavitating propellers and the resulting (low-frequency) hull pressure fluctuations. The hull pressure fluctuations are composed of tonals at harmonics of the blade passage frequency and a broadband part. The relation between the two is analyzed using the modulation theory of MacFarlane. The paper then discusses the consequence of Reynolds number scaling on the wake field of a single screw vessel and on cavitating vortices in general. The influence of air content is also shown for this vessel. A procedure to quantify modulation in model and full scale tests is presented and applied to two test-cases.