XIONG Ziying ZHU Xiqing LIU Xiaolong LI Ya

(China Ship Scientific Research Center  P.O.Box 203, Andong, 760-749, Korea)

Received Oct. 21, 2008

Revised Mar. 2, 2009

Abstract The mechanism and prediction methods of low-frequency discrete spectrum noise of ducted propellers are studied. The acoustic pressure field of ducted propellers is divided into the propeller radiated field and the duct scattered field based on the linear acoustic theory. First of all, the flow fields is analyzed with unsteady panel method to get the unsteady force, and then the pressure data are used as the sources for Ffowcs Williams-Hawings formulation to predict the propeller radiated field, meanwhile, the duct scattered field is obtained by Kirchoff integral equation. Through the analysis an calculation of a ducted propeller case, it is found that the duct scattered sound field is a small quantity compared with propeller radiated sound field under low-frequency and short duct condition; Also the predicted discrete spectrum noise level of ducted propellers is compared with that of full-scale propellers by experiment, verifying the predicted results are able to reflect the full-scale propellers’ discrete spectrum noise level properly. 　　　

PACS numbers: 43.30, 43.50