On Higher Order Blade Harmonics of Propeller-Excited Hull Pressures Due to Cavitation - A Review and Discussion Free

Cavitating tip vortices, higher harmonic order hull pressure fluctuations, and PD- as well HDNC-technique for cavitation nuclei measurements are treated in this paper. - In section 2 earlier measurements of propeller excited pressure fluctuations with the detection of the 2^nd harmonic blade order of a three-bladed propeller are described. This 2^nd order is caused by the displacement effect of the tip vortex with nodes, that in section 3 is theoretically treated by a velocity potential for a hollow vortex with nodes based on a theory by Ackeret. Calculated results and experiments agree reasonably well. Section 4 contains reflections and discussions on further flow effects of cavitating tip vortices, e. g. vortex bursting. In section 5 higher order hull pressure fluctuations from two water tunnels and full scale are compared, and the occurred scale effects between model and full scale results are discussed. In section 6 a comparison of nuclei concentrations from the PD- and HDNC-techniques is shown; also the question, whether solid particles serve as cavitation nuclei, is addressed. Finally in section 7 a conclusion is drawn.