On the Method of Roughness Analysis of Ship Hull surface
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概要
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Among few methods of roughness analysis of ship hull surface, the one proposed by Dr. Conn, in 1953 is well known. In this method a diagram is drawn showing the relation between the mean apparent amplitude and the apparent frequency of surface roughness. The diagram is easily obtained Providing that the surface roughness is recorded correctly by means of roughness recorders, so this method is much more practical than the troublesome Fourier's Analysis. However, this method gives less information about rough surface.<BR>What we do in the method is to compare the mean height of protuberances between different surfaces. And there is no knowing about the relation between the mean apparent amplitude and energy spectrum of rough surface.<BR>This paper shows theoretically how to read this diagram properly on the base of probability calculation and also presents that the mean apparent amplitude (function of the apparent frequency of surface roughness) is almost independent of the energy spectrum, but depends on the probability density (for instance a normal distribution) of the ordinate of the surface. This means that the height of the surface belongs to a random process and that any rough surface must essentially have the same mean apparent amplitude except that it is proportional to the standard deviation of the probability density of the height of the roughness.<BR>But if we make use of this fact inversely, we can check the validity of the data obtained.<BR>Besides, this paper shows the method to obtain the smallest wave length of the data curve, which gives the order of smoothness of the surface.
- 社団法人 日本船舶海洋工学会の論文
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