prediction of line-spectrum noise induced by high speed vehicle counter-rotation propellers in water

Line-Spectrum noise of counter-rotation propellers has constituted the main part of radiated noise of high speed vehicles in water.The line spectrum noise of the counter-rotation propellers is due to the interactions between fore or aft propeller and wake of the vehicle,and the interaction between fore and aft propeller.Based on a combination of the lifting sllrface theory and acoustic thecniques,the prediction method of line-spectrum noise is presented in this paper.Theoretical calculation method,characteristics and numerical predition of the line-spectrum noise are detailed in this paper.The effect of different wake and different distance between fore and aft propeller on the propeller noise is also studied by numerical method.The agreement of predicted results compared with existing experimental data is quite satisfactory.So that,the methods are to have important values for performance prediction of the vehicle.inspection of the noise sources and acoustic design of counter-rotation propellers,etc.