Features of broadband unsteady force acting on a propeller induced by grid turbulence

Abstract

To study the characteristics of the excitation source of low-frequency broadband noise radiated from a ship propeller, the broadband spectra of the unsteady thrust of a model-10 blade propeller induced by grid turbulence are calculated using the correlation method. Under various conditions, the relative magnitudes of each component in the total unsteady thrust are evaluated. The accuracy of the correlation method is validated by comparing the experimental results. Based on this method, the evolution characteristics of the broadband unsteady force response of the propeller are investigated from three perspectives: operating conditions, flow characteristics, and propeller geometry. Results show that, first, the amplitude of broadband hump at blade passing frequency is approximately linear to the quadratic power of the rotation speed under similar operating conditions; second, the critical integral scale is inversely proportional to the number of blades; third, the unsteady broadband force cannot be reduced by rake, and the lateral oblique angle distribution of polynomial is better than that of linear distribution in controlling the broadband peak of blade frequency.