油回収船まわりの油膜の挙動

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The behavior of oil film around a running ship should be studied for dsveloping efficient oil spill recovery ships. The efficiency of the oil recovery equipment, for instance, largely depends upon the oil film thickness at the position where the equipment is set up in the ship. The law of similitude should be also clarified to investigate the performance of oil spill recovery ships through model experiments. In the present paper, a model is proposed for the mechanisum of flow in oil film due to motion of a ship and validated experimentally. Diamond-shaped models 30cm long were towed in oil films of various thickness in a tank of 150cm(L)×36cm(B)×22cm(d). The distributions of oil film thickness were measured on photograghs taken through the glass side-wall of the tank. The following are concluded from the experiments ; (1) The flow in oil film around a ship is replaced with a supercritical flow in a shallow open channel of the depth equated with the oil thickness in the gravity of gα, where α=(ρ_2-ρ_1)/ρ_1, ρ_1 and ρ_2 are density of oil and water respectively. (2) The behavior of oil film is, therefore, governed by densimetric Froude number, M_0=V/√<gαh_0>, where V is ship speed and h_0 is oil thickness at infinity. The shock waves around models of diamond-shaped water lines derived from the above replacement agreed well with results of experiments. (3) Tests with a geometrically similar model including the oil film can simulate the full scale phenomena when Froude similitude is applied. The geometric similitude, however, usually leads an unrealistically thin oil film in model scale, and then a distortion of similitude is applicable using the different scale ratios in the horizontal and vertical direction.
社団法人日本船舶海洋工学会の論文
1981-03-30

油回収船まわりの油膜の挙動

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