楔型物体の水面衝撃

概要

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Impact of a wedge body dropping on a water surface is analyzed by means of the boundary element method. Wagner's theory predicts maximum pressure in good agreement with experimental results in case of larger deadrise angle β>15゜. In case of small deadrise angle, however, there is a large discrepancy between experiments and the theory, which gives an infinitely large pressure in the limiting case P→0°. In reality, pressure is reduced due to air cushioning effects. The present paper concerns with the behavior of the wedge of an intermediate deadrise angle, 1°≦β≦5°, and air cushioning effects are shown to be neglected for β>3°. In the present calculation, the water is idealized by boundary elements, and the instantaneous configuration of free surface and the wedge body are determined by considering the fluidsolid intersection. Numerical and experimental results show the variation of maximum pressure along the width depending on the dropping conditions, which is in contrast to Wagner's theory predicting uniform distribution. The relation between the maximum pressure caused by dropping at constant speed and that by dropping freely is also shown as a function of wetted width and impact velocity. In order to improve accuracy of numerical results, the splash condition should be included in the analysis, which will be left to further study.
社団法人日本船舶海洋工学会の論文