Research on Problems of Stern Flow and Propulsive Performance Considering the Interaction between Ship Hull and Propeller

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At first we carried out the research on analytical characteristics of oscillating pressure distribution avobe a propeller. The calculated and meadured results for a five-bladed propeller have shown the normal distribution of oscillating pressure in cases of a uniform flow and cos2<theta> wake flow but an abnormal distribution in case of co5<theta> wake flow.Secondly we investigated into the influence of boundary layer and wake on free surface flow around a ship model. The Rankine-source method was combined with an integral method for boundary laver and wake under the boundary condition on the free surface considering the total head loss due to viscosity, The computed results as for wave profiles, pressure distributions and resistances were shown in comparison with measurements.Thirdly we performed measurement of the velocity field in the rear region of a model propeller using the laser-doppler velocimeter in the experimental tank. The results made clear the necessity of seeding to detect the slow turning velocity in propeller race and the availability of stators installed just behina the propeller. As the next step we carried out measurement of the velocity fields around the rudder in the uniform flow and in the slip-stream of the propeller using the laser-doppler velocimeter. The measured results showed clearly the interaction between the rudder and the propeller.Finally the unsteady characteristics of the propeller and the rudder were calculated using the voxted lattice method in order to investigate the interaction between the propeller and the rudder. The effects of the rudder on the propeller were found as 7[14% fluctuations of thrust and torque of the propeller and as 2[3% up of the propeller efficiency.