With the recent increasing interest in scientific and engineering researches into ocean and deep sea, larage and high powered oceanographic ships with controllable pitch propellers (CPPs) has become necessary.
In such ships, because of necessity for detection of the deep sea bottom and telephoning and communication between the support ship and the deep sea submergence vehicle using acoustic instruments, it has become a very important technical object to reduce the underwater noise around the hull, especially the propeller cavitation noise, below the required level.
In this paper, firstly, general relations among properller geometry, cavitation and noise are explained, considering characteristics of CPP, and the f ollwing three fundamental methods which are found effective for reduction of the propeller noise are described
1) Equalization of wake distribution at a properller plane
2) Optimum selection of particulars and shape of CPPs
3) Optimum combination of CPP blade angle and revolution number Secondly, theoretical and experimental studies of the low noise CPP on the support ship“Yokosuka”for a 6500m deep submergence research vehicle in application of the above methods are briefly described.
The full scale propeller noise was measured at her sea trial and compared with the predicted one. It was found that the noise level of this propeller was very low and the above described methods were very effective for the noise reduction.
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