Research on the Scale Effect of Water Impact

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Since it is hardly to see flat surface in high seas, a three-dimensional theory taking effects of distortion of the water surface into account has been developed as-a main feature of this research. It is possible to discuss about the trapped air by this theory without a difficulty at a corner of the body which is found in the previous theories. Objectives of this research are investigating the influence of trapped air, elasticity and three-dimensional distortion and explaining the scale effects which arises when the experimental results are converted into the ship scale by obeying Floude's law. New theory stated above is the main body of this research to achieve the objectives.The following results has been obtained during this three-years research. When the bottom has the elasticity, if the elasticity is taken into account the linear theory would give good results and it suggests that the effect of air-flow is negligible. When the water surface is distorted, the reduction by the trapped air is not big, however the averaged impact pressure is greatly reduced. In the case of the axisymmetrical body. With attached cavity, the linear theory gives good estimations of pressure of the trapped air. Therefore, it is stated that the linear theory is good enough to predict the impact pressure when the water surface is not flat. Then, the scale effect between the model scale and the ship scale has been investigated by this theory and it is found that the scale effect is big. But, the general method to predict the scale effect has not been obtained because the scale effect is strongly depend on the shape of the body and the entry speed.