To investigate the effects of the caudal fin deformation on the hydrodynamic performance of the self-propelled thunniform swimming, we perform fluid-body interaction simulations for a tuna-like swimmer with thunniform kinematics. The 3-D vortices are visualized to reveal the role of the leading-edge vortex (LEV) in the thrust generation. By comparing the swimming velocity of the swimmer with different caudal fin flexure amplitudes f_a, it is shown that the acceleration in the starting stage of the swimmer increases with the increase of f_a, but its cruising velocity decreases. The results indicate that the caudal fin deformation is beneficial to the fast start but not to the fast cruising of the swimmer. During the entire swimming process, the undulation amplitudes of the lateral velocity and the yawing angular velocity decrease as f_a increases. It is found that the formation of an attached LEV on the caudal fin is responsible for generating the low-pressure region on the surface of the caudal fin, which contributes to the thrust. Furthermore, the caudal fin deformation can delay the LEV shedding from the caudal fin, extending the duration of the low pressure on the caudal fin, which will cause the caudal fin to generate a drag-type force over a time period in one swimming cycle and reduce the cruising speed of the swimmer.

为了研究尾鳍变形对自行式苏打形游泳的水动力性能的影响，我们对具有苏打形运动的金枪鱼状游泳者进行了流固耦合仿真。将3-D涡旋可视化以揭示前沿涡旋（LEV）在推力生成中的作用。通过比较不同尾鳍挠曲幅度f _a的游泳者的游泳速度，可以看出游泳者开始阶段的加速度随着f _a的增加而增加。，但巡航速度降低。结果表明，尾鳍变形有利于快速起步，但不利于游泳者的快速巡航。在整个游泳过程中，横向速度和偏航角速度的波动幅度随f _a的增加而减小。发现在尾鳍上形成附着的LEV负责在尾鳍表面上产生低压区域，这有助于推力。此外，尾鳍变形会延迟LEV从尾鳍脱落的时间，延长尾鳍上低压的持续时间，这将导致尾鳍在一个游泳周期的一段时间内产生阻力型力，并且降低游泳者的巡航速度。