Study on Propulsive Performance of Marine Animal in Swimming Motion

有数据表明，海豚的游泳速度可能与它们的体长(L)成正比。实现了低阻力、高推进效率或高肌力。这项研究的目的是通过实验模型来确定海豚可以做出什么样的游泳动作来提高它的推进效率。本研究分为三个步骤；也就是说，第一步是研究真实海豚的游泳动作；第二步是制作模型；第三步是对模型进行实验。第一步，记录并分析了海豚的仰泳动作。结果表明，它的运动是占用和暗示的重复，并且看起来像2节点梁振动，即它的运动属于驻波形式。J. Lighthill爵士的理论总结如下。对于希望有效地推动自己并在水中达到高速的海洋动物来说，必须通过身体下面的行波。但此处观测到的驻波效率不能超过50%。为了弄清驻波是否有效，建立了一个以驻波为运动方向的模型。对于刚构模型，其体强度存在问题。然后，在本研究中，采用弹性体结构，即纵向强度构件采用钢琴丝。模型长度为0.3m（1/10比例）。钢琴线的尺寸是根据相似定律决定的。在拖曳箱中进行了阻力试验和游泳试验。在游泳试验中，最大速度为0.5m/s。

There are the data that swimming speed of dolphin may be proportional to their body length (L). Low resistance, high propulsive efficiency or high muscle power has been realized.The objective of the study is to determine experimentally with a model what swimming movements a dolphin can make which will give it high propulsive efficiency. This study is composed of three steps ; that is, the 1st step is to investigate swimming movements of real dolphin ; the 2nd step is to make a model ; the 3rd step is to make experiment with the model. At the 1st step, back stroke swimming movements of a dolphin were recorded and analyzed. From the results, it has shown that its movements are repetition of hogging and sugging, and looks like 2-node beam vibration, that is, its movemets belong to standing wave form.Sir J. Lighthill were concluded theoretically as follows. For marine animals wishing to propel themselves efficiently and to attain high speed through water, it is necessary to pass a raveling wave beneath the body. But efficiency of the standing wave form here observed cannot exceed 50%. To clarify whether the standing wave form is efficient or not, a model which moves by standing wave form has been made.For rigidly constructed model, there are problems on the strength of its body. Then, in this study, the elastic body construction was adopted, namely, piano-wires were employed for longitudinal strength member. The model length was 0.3m (1/10 scale). Size of piano-wire has decided in consideration of the law of similitude.Both resistance tests and swimming tests were carried out in the towing tank. In the swimming tests, the maximum speed was 0.5m/sec.