Study on Propulsive Performance of Marine Animal in Swimming Motion

有资料表明，海豚的游泳速度可能与其体长（L）成正比。低阻力、高推进效率或高肌肉力量已经实现。本研究的目的是用模型实验确定海豚可以做出什么样的游泳运动来使其具有高推进效率。本研究分为三个步骤：第一步是对真实的海豚进行游泳动作的研究;第二步是制作模型;第三步是对模型进行实验。在第一步，记录并分析了海豚的仰泳动作。结果表明，它的运动是中拱和中拱的重复，类似于二节点梁的振动，即它的运动属于驻波形式。对于希望有效地推进自己并在水中获得高速的海洋动物来说，有必要在身体下方通过一个松散的波浪。但是这里观察到的驻波形式的效率不能超过50%。为了验证驻波形式是否有效，建立了一个以驻波形式运动的模型，对于刚性结构的模型，其本体的强度存在问题。然后，在本研究中，采用弹性体结构，即钢琴丝作为纵向强度构件。模型长度为0.3m（1/10比例）。在拖曳水池中进行了阻力试验和游动试验。在游泳测试中，最大速度为0.5米/秒。

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.