斑海豹胡须涡激振动及其尾流循迹机理直接数值模拟

VORTEX-INDUCED VIBRATION AND WAKE TRACING MECHANISM OF HARBOR SEAL WHISKER:A DIRECT NUMERICAL SIMULATION

在视力和听力受到限制的条件下,斑海豹可以通过具有特殊外形的胡须识别和追踪水中游鱼的尾迹.从仿生学的角度,对斑海豹胡须在尾迹流场中的振动特性和循迹机理进行研究,有助于开发研制新型水下探测器.本文采用嵌入式迭代浸入边界法,在雷诺数Re=300和折合流速Ur=6.0的条件下,对均匀流场和尾迹流场中斑海豹胡须模型的涡激振动进行直接数值模拟,研究了胡须模型的振动特征和尾涡结构,并与具有相同等效直径的圆柱、椭圆柱的振动响应进行对比,分析了不同结构外形对振动特性和尾涡结构的影响,探讨了斑海豹胡须的感知能力和循迹机理.模拟结果表明,胡须结构具有显著的减阻、抑振作用,在均匀流场中做微幅混沌运动,这为斑海豹胡须感知提供了纯净的信号背景.而在尾迹流场中,胡须结构的振动响应显著增强,稳定且周期性好,与其他柱体相比,具有更高的信噪比和敏感度.这揭示了斑海豹利用胡须振动识别和追踪水中游鱼尾迹的机理,对于开发研制新型水下探测器具有重要借鉴意义.

Even without eyesight and hearing,harbor seal can identify and track the wake of swimming fish in the water by its whiskers with a special shape.From the biomimetic point of view,study on the vibration responses and the tracking mechanisms of harbor seal whisker in wake flow contributes to the development of a new-type underwater sensor.In this paper,direct numerical simulation of the vortex-induced vibration of the harbor seal whisker in uniform and wake flow with a Reynolds number of Re=300 and a reduced velocity of Ur=6.0 was performed by applying the iterative immersed boundary method.The vibration characteristics and the wake structures of the whisker models are investigated and compared with those of a circular cylinder and an elliptical cylinder with the same equivalent diameter.The effects of different structural shapes on the vibration characteristics and wake structures are analyzed,and the sensing ability and tracking mechanisms of the harbor seal whisker are discussed.The simulation results show that the whisker model can significantly reduce the drag force and suppress the vibration responses in uniform flow.It undergoes a chaos motion with a very low amplitude,which provides a pure signal background for harbor seal’s whisker for sensoring.However,in wake flow,the vibration response of the whisker model increases significantly,being stable and periodic.As a result,the whisker model has a higher signal-to-noise ratio and sensitivity than other cylinders.This reveals the mechanism of harbor seal using its whiskers to identify and track the wake of swimming fish in the water,which is of great significance for the development of a new-type underwater detector.