Comparison of Wake Distributions between Ship and Model

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Velocity distributions were measured by 5-hole pitot tubes at the section about 1.1D before the propeller on a ship and the models, as shown in Fig. 3. The lengths of the ship and models are 167m, 8.267m and 4.5m respectively. The smaller model was used for the preliminary tests to plan the full-scale measurements. The measured results are shown in Figs. 7 to 12 both for the ship and models. Principal conclusions obtained are as follows; (1) Velocity distributions in the boundary layer does not follow the 1/n law and shows the tendency of seperation, at the measured section, which is more remarkable on the models than on the ship, as shown in Fig. 13. (2) The pattern of V_X/V and the vector of V_<YZ>/V are coincided well in tendency between the ship and models except the region near the hull at the shaft center line. (3) So-called stern vortex is affected by Reynolds no., and the vortex of the ship is shrinked by more than the ratio of thicknesses of the boundary layers between the ship and model. (4) According to the three dimensional expression of the flow around the stern, shown in Fig. 18, the flow before the propeller attains to the propeller disc, keeping the general tendency constant, including the complicated flow of vortex. This fact will give a hint to obtain the better estimation for wake values of the ships. (5) The values of (1-w_s)/(1-w_M) calculated by various methods are shown in Table 2.
社団法人日本船舶海洋工学会の論文