Study on Scale Effect of the Resistance due to Stem Wave Breaking

(1)澄清尾轴后的水流结构通过对尾轴后水流的详细观察，澄清了尾轴后的水流在水面上存在反向流动，反向流动被尾轴端阻挡，然后沿尾轴端向两侧流动，最后流出成为侧流。实验也证实了反向流动是由于正向破波而产生的。(2)处理前向破波方法的发展斜尾阀杆后的水流已近似为滑面波。提出了正向破波发生的判据。在此基础上，提出了一种估算水面下流层破裂厚度的方法和估算正向破波阻力的方程。(3)前向破波特性的澄清利用2中所发展的方法对该现象进行的研究表明，该现象与本研究开始时假设的一样，受茎端垂直流速分布的影响较大，因此具有尺度效应，且随着模型船尺寸的增大而减小的无量纲阻力系数。另一方面，研究表明，随着模型船尺寸的增大，在舰干端产生的未破碎后传播的剩余随波高度反而增大。(4)今后的研究计划：首先研究剩余的后续波浪。其次，利用所建立的方法研究了由两种不同特征分量组成的正向破波和剩余随波的尺度效应。

(1) Clarification of the water flow structure just behind a transom stemThe detailed observation of water flow just behind a transom stem has clarified that reverse flow exists on water surface there and that the reversed flow is blocked out by the stem end and then flows along the stem end towards both sides and finally goes out into side flow. It has been also exprimentally confirmed that the reverse flow is generated as a result of forward-oriented wave breaking.(2) Development of methods to treat forward-oriented wave breakingWater flow just behind a transom stem has been approximated with trochoidal wave. Criteria for forward-oriented wave breaking occurrence have been proposed. Based on these, a method to estimate what thickness of flow layer under water surface breaks and an equation to estimate resistance due to forward-oriented wave breaking have been developed.(3) Clarification of forward-oriented wave breaking characteristicsStudies of the phenomenon by the methods developed in 2 have clarified that the phenomenon is much affected by the vertical flow speed distribution at stem end as assumed at the start of this study, it has, therefore, scale effect and non-dimensional coefficient of resistance due to the phenomenon decreases with increase of model ship size. On the other hand, it has been clarified that height of remained following waves, which is generated at stem end, not broken and propagated afterwards, increases with increase of model ship size to the contrary.(4) Study plan from nowRemained fallowing waves is to be studied at first. Next, scale effect of stem waves which consist of two components different in characteristics forward-oriented wave breaking and remained following waves is to be studied by the methods developed.