Liu Nansheng, Peng Yan, Liang Youwen, Lu Xiyun
Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui, China.
Phys Rev E Stat Nonlin Soft Matter Phys. 2012 May;85(5 Pt 2):056316. doi: 10.1103/PhysRevE.85.056316. Epub 2012 May 30.
Flow over a traveling wavy foil with a passively flapping flat plate has been investigated using a multiblock lattice Boltzmann equation and the immersed boundary method. The foil undergoes prescribed undulations in the lateral direction and the rigid flat plate has passive motion determined by the fluid structure interaction. This simplified model is used to study the effect of the fish caudal fin and its flexibility on the locomotion of swimming animals. The flexibility of the caudal fin is modeled by a torsion spring acting about the pivot at the conjuncture of the wavy foil and the flat plate. The study reveals that the passively oscillating flat plate contributes half of the propulsive force. The flexibility, represented by the nondimensional natural frequency F, plays a very important role in the movement and propulsive force generation of the whole body. When the plate is too flexible, the drag force is observed. As the flat plate becomes more rigid, the propulsive force that is generated when the undulation is confined to last part of the wavy foil becomes larger. The steady movement occurs at F=5. These results are consistent with the observations of some swimming animals in nature.
利用多块格子玻尔兹曼方程和浸入边界方法，对具有被动摆动平板的行进波箔上的流动进行了研究。箔片在横向方向上经历规定的波动，刚性平板具有由流固相互作用决定的被动运动。这个简化模型用于研究鱼尾鳍及其柔韧性对游泳动物运动的影响。尾鳍的柔韧性通过作用在波箔和平板结合处枢轴上的扭簧来建模。研究表明，被动振荡平板贡献了一半的推进力。以无量纲固有频率F表示的柔韧性在整个身体的运动和推进力产生中起着非常重要的作用。当平板过于柔韧时，会观察到阻力。随着平板变得更硬，当波动局限于波箔的最后部分时产生的推进力会更大。在F = 5时出现稳定运动。这些结果与自然界中一些游泳动物的观察结果一致。
