船体を貫通する垂直方向の開口部における流体の挙動とその影響

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Recently some ships have been constructed with a vertical well which have the bottom opening for the purpose of raising and lowering the equipment. Some examples are vesseltype drilling rigs, vessels carrying small submersibles and so on. This paper shows the behavior of the water in the well, and its effects on the motion of the ship, when she is running. Eperimental studies were performed under two different sets of conditions. (1) The motion of the free water surface in the well was studied, when the ship-model was fixed stationary in the stream. (2) The effect of the motion of the water in the well on the motion of the ship-model was studied, when the model was towed. The following conclusions were obtained. 1) When the ship-model with a well is fixed stationary in the stream, it can be observed that the water surface moves regularly in it. This phenomenon is similar in many respects to the motion of ader which is elastically supported by springs in the stream. 2) The type of water motion, whether up and down, right and left or forwards and back-wards, depends on the velocity of the stream and the shape of the well. 3) The water motion can be seen at the dimensionless stream velocity of 0.2<2U/l_0<1.6, where U is the stream velocity, I is the length of the bottom opening and coo is the natural circuiar frequency of the water movig in the well. 4) The experimental values agree well with the results of the theoretical calculation on the heaving amplitude of the free water surface in the well, and on the increased drag of the ship-model by the motion of water in it. 5) In order to reduce the motion of water in the well, it is very effective to fix short flanges on its vertical walls a little below the water surface.
社団法人日本船舶海洋工学会の論文

船体を貫通する垂直方向の開口部における流体の挙動とその影響

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