PREDICTING CAVITATION EROSION OF SHIP PROPELLERS FROM THE RESULTS OF MODEL EXPERIMENTS

A method was develped to predict the service life of propellers as a function of ship operating conditions based on the results of water tunnel of scale models. The method involves quantitative measurement of the erosive nature of cavitation in terms of the "erosive impact intensity" which is defined as the rate of formation and the size distribution of cavitation bubble collapse pits formed on a soft metal exposed to the cavitation. Model tests demonstrated that the erosive impact intensity so measured is very sensitive to propeller design and simulated operating conditions and should be a useful criterion for optimization of propeller design. Erosive impact intensity of cavitation measured on a full-scale propeller provided knowledge of the scaling relationships for cavitation erosion and led to the formulation of an equation to predict erosion rates of propellers in service.