Department of Engineering Science, University of Oxford, Oxford, OX1 3PJ, UK.
School of Engineering, Cardiff University, Cardiff, CF24 3AA, UK.
Sci Rep. 2022 Jul 25;12(1):12660. doi: 10.1038/s41598-022-16181-8.
Many aquatic and aerial animal species are known to utilise their surrounding flow field and/or the induced flow field of a neighbour to reduce their physical exertion, however, the mechanism by which such benefits are obtained has remained elusive. In this work, we investigate the swimming dynamics of rainbow trout in the wake of a thrust-producing oscillating hydrofoil. Despite the higher flow velocities in the inner region of the vortex street, some fish maintain position in this region, while exhibiting an altered swimming gait. Estimates of energy expenditure indicate a reduction in the propulsive cost when compared to regular swimming. By examining the accelerations of the fish, an explanation of the mechanism by which energy is harvested from the vortices is proposed. Similar to dynamic soaring employed by albatross, the mechanism can be linked to the non-equilibrium hydrodynamic forces produced when fish encounter the cross-flow velocity generated by the vortex street.
许多水生和飞行动物物种都被发现利用周围的流场和/或邻居产生的诱导流场来减少体力消耗，然而，这种好处是如何获得的机制仍然难以捉摸。在这项工作中，我们研究了在产生推力的振荡水翼尾流中虹鳟鱼的游动动力学。尽管在涡街的内部区域存在更高的流速，但一些鱼仍保持在这个区域，同时表现出改变的游动步态。对能量消耗的估计表明，与常规游泳相比，推进成本降低了。通过检查鱼的加速度，提出了一种解释从涡旋中获取能量的机制。类似于信天翁采用的动力翱翔，该机制可以与鱼遇到涡街产生的横向速度时产生的非平衡水动力联系起来。
