Surface Force Measurements of Actual Ship with Controllable Pitch Propeller

Abstract

The fluctuating pressure on the hull surface just above the propeller was measured and at the same time, the behavior of propeller cavitation observed by the case of the training ship "FUKAE MARU" of Kobe Mercantile Marine University. She has a overall length of 50 meters, a displacement of 784 tonnes, and a CPP with a diameter of 2.1 meters, with skewed angle of 40 degrees and with anti-clockwise revolution viewing from stern. Two pressure sensors were embedded in the hull surface so as not to disturbe the flow. The underwater video camera and the underwater strobe light were mounted on the port side hull near stern. Measurement trials were carried out over the certain ranges of blade angle and propeller revolution number. The trials made clear the followings, (1) as the propeller load increases, the pressure fluctuation increases and the cavitation developes further, (2) the increase of the pressure fluctuation becomes very rapid and the very sharp peak appears in the fluctuating wave when the cavitation occurs, (3) in the case of turning run, the fluctuating pressure is not so large as that of the straight run, and, when the turning direction is opposite to the direction of the propeller revolution, high frequency components appear distinctively.