The work in this paper focuses on the examination of the effect of variable stiffness distributions on the kinematics and propulsion performance of a tuna-like swimmer. This is performed with the use of a recently developed fully coupled fluid-structure interaction solver. The two different scenarios considered in the present study are the stiffness varied along the fish body and the caudal fin, respectively. Our results show that it is feasible to replicate the similar kinematics and propulsive capability to that of the real fish via purely passive structural deformations. In addition, propulsion performance improvement is mainly dependent on the better orientation of the force near the posterior part of swimmers towards the thrust direction. Specifically, when a variable body stiffness scenario is considered, the bionic body stiffness profile results in better performance in most cases studied herein compared with a uniform stiffness commonly investigated in previous studies. Given the second scenario, where the stiffness is varied only in the spanwise direction of the tail, similar tail kinematics to that of the live scombrid fish only occurs in association with the heterocercal flexural rigidity profile. The resulting asymmetric tail conformation also yields performance improvement at intermediate stiffness in comparison to the cupping and uniform stiffness.

本文的工作重点是研究可变刚度分布对类似金枪鱼的游泳者的运动学和推进性能的影响。这是使用最近开发的全耦合流固耦合求解器来完成的。本研究中考虑的两种不同情况是刚度分别沿鱼体和尾鳍变化。我们的结果表明，通过纯粹的被动结构变形复制与真鱼相似的运动学和推进能力是可行的。此外，推进性能的提高主要取决于游泳者后部附近的力更好地朝向推力方向。具体来说，当考虑可变车身刚度场景时，与先前研究中通常研究的均匀刚度相比，在本文研究的大多数情况下，仿生身体刚度曲线会产生更好的性能。鉴于第二种情况，刚度仅在尾部的展向方向变化，与活鲭鱼相似的尾部运动学仅与异尾弯曲刚度分布相关联。与杯突和均匀刚度相比，由此产生的不对称尾部构象在中等刚度下也产生了性能改进。与活鲭鱼相似的尾部运动学仅与异尾弯曲刚度分布有关。与杯突和均匀刚度相比，由此产生的不对称尾部构象在中等刚度下也产生了性能改进。与活鲭鱼相似的尾部运动学仅与异尾弯曲刚度分布有关。与杯突和均匀刚度相比，由此产生的不对称尾部构象在中等刚度下也产生了性能改进。