Experimental Study on a Wake of Bulk Carrier in a Large Cavitation Tunnel

Abstract

It is important to measure and check the cavitation pattern and vibration around the propeller when they develop ship hull form on the propulsion performance. In this paper, the authors set the flow liner in the cavitation tunnel in order to simulate the flow in fu11 scale, which they estimate from the wake measured in the towing tank. The flow liner is obtained by the idea to make the flow stable, and it is here considered as the body to accelerate the flow near the propeller. They change size and position of the flow liner in the cavitation tunnel and measure the wake at the propeller position. They calculate the flow with the flow liner in the cavitation tunnel by means of Hess and Smith method with the wall effect and the first order approximation of 3-dimensional turbulent boundary layer theory. They get the results that the wake distribution measured with the flow liner in the cavitation tunnel shows better coincidence with the estimated wake distribution in full scale and that the effect of the flow liner on the wake is larger by the potential flow than by the 3-dimensional boundary layer. If the difference of nominal wake fraction between measurement and computation would be due to the vortex distribution with the longitudinal axis, the flow liner will give some effects on the vortex distribution.