Sparks David, Rajeev Edwin, Koley Subhra Shankha, Canestrelli Alberto, Liao James C
Department of Biology, Whitney Laboratory for Marine Bioscience, University of Florida, St Augustine, FL 32080, USA.
Department of Neuroscience, University of Florida, Gainesville, FL 32610, USA.
J Exp Biol. 2024 Dec 1;227(23). doi: 10.1242/jeb.247873. Epub 2024 Dec 5.
Fish in the wild often contend with complex flows that are produced by natural and artificial structures. Research into fish interactions with turbulence often investigates metrics such as turbulent kinetic energy (TKE) or fish positional location, with less focus on the specific interactions between vortex organization and body swimming kinematics. Here, we compared the swimming kinematics of rainbow trout (Oncorhynchus mykiss) holding station in flows produced by two different 3×5 cylinder arrays. We systematically utilized computational fluid dynamics to identify one array that produced a Kármán vortex street with high vortex periodicity (KVS array) and another that produced low periodicity, similar to a parallel vortex street (PVS array), both validated with particle image velocimetry. The only difference in swimming kinematics between cylinder arrays was an increased tail beat amplitude in the KVS array. In both cylinder arrays, the tail beat frequency decreased and snout amplitude increased compared with the freestream. The center of mass amplitude was greater in the PVS array than in only the freestream, however, suggesting some buffeting of the body by the fluid. Notably, we did not observe Kármán gaiting in the KVS array as in previous studies. We hypothesize that this is because (1) vorticity was dissipated in the region where fish held station or (2) vortices were in-line rather than staggered. These results are the first to quantify the kinematics and behavior of fishes swimming in the wake of multiple cylinder arrays, which has important implications for biomechanics, fluid dynamics and fisheries management.
野生鱼类常常要应对由自然和人工结构产生的复杂水流。对鱼类与湍流相互作用的研究通常考察诸如湍动能（TKE）或鱼类位置等指标，而较少关注涡旋结构与身体游泳运动学之间的具体相互作用。在此，我们比较了虹鳟（Oncorhynchus mykiss）在由两种不同的3×5圆柱体阵列产生的水流中保持站位时的游泳运动学。我们系统地利用计算流体动力学来识别一种产生具有高涡旋周期性的卡门涡街的阵列（KVS阵列）和另一种产生低周期性、类似于平行涡街的阵列（PVS阵列），两者均通过粒子图像测速法进行了验证。圆柱体阵列之间游泳运动学的唯一差异是KVS阵列中尾鳍摆动幅度增加。在两个圆柱体阵列中，与自由流相比，尾鳍摆动频率降低，吻部幅度增加。然而，PVS阵列中质心幅度比仅在自由流中时更大，这表明身体受到了流体的一些冲击。值得注意的是，我们并未像之前的研究那样在KVS阵列中观察到卡门步态。我们推测这是因为（1）涡度在鱼类保持站位的区域消散了，或者（2）涡旋是排成一列而非交错排列的。这些结果首次量化了在多个圆柱体阵列尾流中游泳的鱼类的运动学和行为，这对生物力学、流体动力学和渔业管理具有重要意义。
