鱼游尾迹中射流分布特征的数值模拟研究

Numerical investigation of jet in the wake of self-propelled fish swimming

本文采用一种通过控制仿生鱼摆频来达到自主推进状态的数值模拟方法,研究了不同雷诺数下二维仿生鱼自主游动时尾迹中射流的分布特征,并通过模拟两条鱼串列和交错排列时的自主游动,分析了上游鱼的尾迹对下游鱼的影响.结果表明:仿生鱼尾迹中射流的强度随着雷诺数的增大而减小,射流的空间影响域随雷诺数增大而增大;鱼游尾迹中的射流虽然可以导致下游鱼的阻力增加,但能耗却会降低,这与前人的假想恰好相反;而且随着两条鱼间距离的增大,尾迹中的射流会逐渐减弱为低速区,从而导致下游鱼的阻力小于单条鱼游动时的阻力,节能效果更加显著.本文的研究结果将有利于深入理解鱼群中的节能机制以及鱼群的最优排列方式.

We carry out numerical simulations of self-propelled single fish and two fish arranged in tandem and staggered for various Reynolds numbers （Re） using a tail-beat frequency control method, and investigate the distribution characteristics of jet in the wake of a single fish and the influence of the jet induced by the upstream fish on the downstream fish. The results show that the strength of the jet decreases as Re increases, the length of jet zone increases as Re increases. When one fish situates directly behind another one and the distance between them is small, the downstream fish experiences a drag enhancement, but the power consumption is reduced which is opposite to the previous assumption. With the increase of the distance, the drag of the downstream fish decreases gradually till smaller than that for a single fish and the effect of energy saving is more significant. The results will be beneficial to our indepth understanding of the energy-saving mechanism and the optimal arrangement in fish school.