Abstract Oscillating plunging motion is one of the fundamental motions which comprise the kinematics used by many flying and swimming organism for locomotion. It is characterized by the frequency and amplitude of oscillation. Past studies have investigated this motion for relatively small amplitudes. In this paper we investigate reduced frequencies 0.25 ≤ k ≤ 16 and plunge amplitudes 0.03125 ≤ h ≤ 8 to give plunge velocities ranging from 0.25 ≤ kh ≤ 4 at Re = 100. It is found that unlike previous investigations for small plunge amplitudes, thrust does not increase monotonically with kh but reaches a maximum and then decreases reverting back to drag for high h values. It is shown that Leading Edge Vortices (LEVs) are responsible for the production of thrust whereas Trailing Edge Vortices (TEVs) induce drag on the plate. In the regime of increasing thrust with kh, the LEVs and TEVs are not strong enough to influence each other’s trajectory and vortex–vortex interactions are minimal. As kh increases to higher values, LEVs and TEVs gain in size and strength such that vortex induced velocities dominate the flow resulting in strong vortex–vortex interactions. Three main mechanisms of vortex–vortex interactions are identified, which either result in LEVs induced away from the plate or TEVs being induced near the plate. The net effect of these interactions result in reducing the residence time of the LEVs near the plate and decreasing thrust production. Finally, a detailed analysis of the wake is provided for the plunging plate. The inter-vortex distance in the wake is found to correlate directly with plunge amplitude and inversely with frequency. On the other hand, vortex strength is found to be a strong function of reduced frequency (k) where the functional relationship is near linear for different plunge velocities (kh).

中文翻译：

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涡-涡相互作用在下沉平板推力产生中的作用

摘要 摆动俯冲运动是构成许多飞行和游泳生物运动的基本运动之一。它的特点是振荡的频率和幅度。过去的研究已经调查了这种振幅相对较小的运动。在本文中，我们研究了减小的频率 0.25 ≤ k ≤ 16 和俯冲幅度 0.03125 ≤ h ≤ 8，以在 Re = 100 时给出范围从 0.25 ≤ kh ≤ 4 的俯冲速度。发现与之前对小俯冲幅度的研究不同，推力确实不随 kh 单调增加，而是达到最大值，然后减少恢复到高 h 值的阻力。结果表明，前缘涡流 (LEV) 负责产生推力，而后缘涡流 (TEV) 会在板上引起阻力。在随 kh 增加推力的情况下，LEV 和 TEV 的强度不足以影响彼此的轨迹，涡-涡相互作用很小。随着 kh 增加到更高的值，LEV 和 TEV 的尺寸和强度增加，使得涡流引起的速度主导流动，导致强烈的涡旋相互作用。确定了涡-涡相互作用的三种主要机制，它们要么导致远离板块的 LEV，要么导致板块附近的 TEV。这些相互作用的净效应导致减少 LEV 在板附近的停留时间并减少推力产生。最后，对俯冲板的尾流进行了详细分析。发现尾流中的涡间距离与俯冲幅度直接相关，与频率成反比。另一方面，