A method for quantifying the source of flow noise in turbomachines based on acoustic similarity law

A noise source identification method is proposed to separate the noise source function and acoustic response function of the flow noise of turbomachines enclosed by ducts.Based on the acoustic similarity law,the noise source function and acoustic response function are obtained by least square multi linear regression method and Gauss filter respectively.The proposed method is proved to be effective by numerical simulations.The results show that the proposed method is much better than existing methods in terms of the relative errors of noise source function and acoustic response function.Two cases of a computer cooling fan working in free field and in duct are studied subsequently.The noise source function,acoustic response function and sound source tip speed exponent number are calculated by this method and the main components of the sound source are analyzed finally.