Numerical investigation of the impact of speed reduction on propeller excitation

A numerical investigation of the impact of the speed reduction achieved by pitch or propeller Revolutions Per Minute (RPM) variations on propeller performances is proposed. A test case is selected from the European Project AQUO, for which experimental data are available. Numerical self-propulsion analyses are carried out to assess the off-design propeller functioning conditions of the propeller. Results, in terms of self-propulsion points and predicted pressure pulses in the various conditions under investigation (design speed at design pitch, reduced speed at reduced pitch and at reduced RPM), are compared with the available experimental measurements. On the basis of the predicted pressure pulses and cavitation volumes, conclusions are drawn about the acoustic impact of different strategies for realizing off-design operative conditions and on the possibility of ranking them by numerical methods.