Biofluiddynamic Study on Effectivity of Artificial Tail Flukes of Dolphin

海豚游得快，跳得高。从生物工程的角度阐明其生物运动学性能和推进性能具有重要意义。我们知道，尾吸虫在产生高效推进力方面发挥着重要作用。然而，直接测量游泳海豚的推进力是困难的。詹姆斯·格雷指出的问题是，海豚游泳的速度比通过作用于其身体和肌肉力量的流体动力阻力估计的速度更快。这就是众所周知的格雷悖论。在推力方面，重点研究了尾鳍的结构及其在尾鳍摆动下的变形行为。我们认为推进力的估计是通过获得作用在鳍上的流体动力与鳍变形之间的关系来进行的。日本冲绳初老水族馆饲养的一只海豚双尾吸虫进行性坏死，经手术治疗失去了约75%的吸虫。然后为海豚设计了义肢，以帮助海豚像以前一样游泳。对人工尾鳍和海豚尾鳍的力学性能进行了研究。以海豚的尾吸虫为模型制作了人工尾翼，并对其推进性能进行了研究。海豚形机翼在一个振荡周期内几乎产生正推力，且波动较小。我们确信人造尾鳍作为水下航行器的推进器是有用的。利用安装在机翼内部的加速度传感器测量海豚状机翼的行为将在下一阶段进行。

Dolphins swim fast and jump high. It is significant to clarify its biokinematic performance and propulsive performance from the bioengineering viewpoint. We know that the tail flukes play an important role in generating efficient propulsive force. However, it is difficult to measure the propulsive force of swimming dolphin directly. James Gray pointed out the problem that the dolphin can swim faster than at the speed estimated by the hydrodynamic drag acting its body and the power of its muscles. This is well known as Gray's paradox. As for the propulsive force, we paid attention to the structure of the tail fin and its deformation behavior by the fin oscillation. We thought the estimation of propulsive force by obtaining the relationship between the hydrodynamic force acting on the fin and the deformation of the fin.A dolphin kept in Okinawa Churaumi aquarium in Japan suffered progressive necrosis in both tail flukes and lost about 75 % of the flukes by surgical treatment. Then prosthetic flukes for the dolphin were designed in order to assist the dolphin to swim as before. The mechanical properties on the artificial tail fin and a tail flukes of dolphin were investigated. An artificial tail wing modeled on the dolphin's tail flukes was made and the propulsive performance was investigated. The dolphin-like wing almost generated positive propulsive force in one oscillating cycle and its fluctuations were small. We were convinced that the artificial tail fin was useful as the propulsor of underwater vehicles. The measurement of the behavior of the dolphin-like wing using acceleration sensor set inside the wing will be carried out at the next stage.