Design of Propeller Ducts to Reduce Cavitation and Vibration.

A procedure based on inviscid flow theory is detailed for the design of propeller ducts to reduce specific spatial non-uniform in given nominal ship wakes. The objective is to produce net flows to enclosed propellers which will reduce cavitation and vibratory forces. The process yields peripheral variations of camber and conicity angle which will reduce the amplitude of specific wake harmonics to a maximum extent possible under the arbitrarily imposed constraint that the maximum sectional normal force coefficient must not exceed unity. Applications are made to reduce the first shaft of two wakes showing resultant first harmonics reduced by factors of 4 and 1.40 in the 0.8 radius region.