Procedure for Design of Ducts to Reduce Propeller Cavitation and Vibrations

摘要

This study extends and improves the current propeller ducts design procedure, which substantially reduces selected spatial harmonics of any given ship model nominal wake and thus homogenizes the inflow field to the enshrouded propeller. This fact will constitute the most important factor in the study of the ducted-propeller problem since by controlling and homogenizing the propeller inflow field, vibratory characteristics of the system will be minimized and the intermittent blade cavitation will be reduced substantially. The duct shape is determined by means of the so-called 'Penalty Function' which guarantees the minimum value of the propeller inflow field. Three schemes have been studied in the attempt to ameliorate the inflow field. All schemes have been evaluated in terms of the existing propeller-duct interaction program and a conclusion has been reached as to the most advantageous duct shape.