Ship Propeller Performance Prediction under Cavitation

Thaddeus C. Nwaoha & Sidum Adumene

Abstract


 In this study, numerically prediction of the screw propeller design that can overcome cavitation is conducted. The research presents a simplified regression model for the analysis of the geometric area ratio, pitch ratio and open water efficiency of propeller, with the aim of revealing quantitatively the effect of cavitation on propeller open water efficiency. The case study takes into consideration factors that can enhance the performance of a propeller. Area of the propeller disc, propeller pitch ratio, diameter of the propeller, delivered power, thrust coefficient, torque is used as inputs into the model, in prediction of performance for cavitated and non-cavitated propellers. Sensitive analysis is carried out by percentage increase and reduction of the blade area ratio, so as to know the effects on the propeller performance. It is revealed that for every 1% increase in the expanded blade areas, the open water efficiency decreases at 0.12% and 0.15% for the non-cavitated and cavitated propellers respectively. This indicates a performance reduction by a cavitation factor of 0.03. The study further shows that at 7.5% reduction in the expanded blade area ratio, the propeller performance in terms of open water efficiency, increases by 1.85%. The analysis exposed an appropriate and accurate operating envelope for optimal screw propeller performance, thus revealing a way of minimizing cavitation effect.


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