Department of Mechanical and Aerospace Engineering and Center for Urban Science and Progress, New York University Tandon School of Engineering, 370 Jay Street, Brooklyn, 11201, NY, USA; Department of Mechanical Engineering, Tennessee Technological University, 115 W. 10th Street, Cookeville, 38505, TN, USA.
Mechanical and Mechatronics Engineering Department, University of Waterloo, 200 University Avenue West, Waterloo, N2L 3G1, ON, Canada.
J Theor Biol. 2023 Jan 7;556:111313. doi: 10.1016/j.jtbi.2022.111313. Epub 2022 Oct 17.
Elucidating the hydrodynamics of fish swimming is critical to identifying the processes underlying fish orientation and schooling. Due to their mathematical tractability, models based on potential flow are preferred in the study of bidirectional interactions of fish with their surroundings. Dipole-based models that assimilate fish to pairs of vortices are particularly enticing, but yet to be thoroughly validated. Here, we embark on a computational fluid dynamics (CFD) campaign informed by experimental data to validate the accuracy of dipole-based models. The locomotory patterns of a fish undergoing carangiform swimming are reconstructed from existing experimental data, which are used as inputs to CFD simulations of a fish swimming in a channel flow. We demonstrate that dipole-based models are accurate in capturing key features of the fluid flow, but cannot predict the elongated flow streamlines around the fish that are evident in CFD. To address this issue, we propose an alternative model that replaces each vortex in the pair with a sheet along the fish length. Using a pair of vortex sheets that span approximately 80% of the fish body length with a separation distance of approximately 50% of the body width, the model is successful in predicting the fluid flow around the swimming fish for a range of background flow speeds and channel widths. The proposed model shows improved accuracy at the cost of a mildly increased computational effort, thereby constituting an ideal basis for research on fish hydrodynamics.
阐明鱼类游动的水动力对于确定鱼类定向和群体游动的基础过程至关重要。由于其数学上的易处理性，基于势流的模型在研究鱼类与周围环境的双向相互作用中被优先采用。基于偶极子的模型将鱼类简化为一对涡旋，特别吸引人，但尚未得到彻底验证。在这里，我们根据实验数据开展了计算流体动力学 (CFD) 研究，以验证基于偶极子的模型的准确性。从现有的实验数据中重建了鱼类进行鲭形游动的运动模式，将其作为输入用于在通道流中游泳的鱼类的 CFD 模拟。我们证明，基于偶极子的模型可以准确地捕捉到流场的关键特征，但不能预测到 CFD 中明显存在的围绕鱼类的拉长流线。为了解决这个问题，我们提出了一种替代模型，用沿鱼体长的薄片代替对中的每个涡旋。使用一对约占鱼体长 80%的涡旋片，间距约为体宽的 50%，该模型成功地预测了一系列背景流速和通道宽度下游泳鱼类周围的流场。该模型在略微增加计算工作量的代价下提高了准确性，从而为鱼类水动力研究提供了理想的基础。
