串列仿生鱼自主游动的数值模拟研究

采用自适应网格下的ghost-cell浸没边界方法,数值模拟了两条串列仿生鱼在相同摆频条件下的自主游动,并通过引入节能效率的概念分析了串列游动中的节能效果。通过与相同参数下单条仿生鱼自主游动的比较,发现串列仿生鱼的自主游动速度要大于单条鱼的速度。下游鱼的阻力会增加,但功耗会减少,表明下游鱼从上游鱼的尾涡中吸收了能量,达到了节能的效果。当水平间距较小时,下游鱼会对上游鱼产生一定的反推作用,从而使其阻力减小。结果还表明,高推进效率并不意味着高节能效率,从整体平均节能效果来看,反相位游动时节能效果比同相位时显著,平均节能效率达到22.4%。

Numerical simulation of two self-propelled fish swimming in a tandem arrangement

Using an adaptive version of immersed boundary method,the self-propelled swimming of two tandem fish with the same tai-beat frequency was investigated numerically.The energy-saving effect was analyzed by introducing a novel concept of energy-saving efficiency.The results show that the self-propelled swimming speeds of the two tandem fish are higher than that of single fish.The drag of the downstream fish is increased,and the power consumption is reduced,which means the downstream fish can extract energy from the vortex induced by the upstream fish.On the other hand,the upstream fish can also benefit from the downstream fish when the streamwise distance between the two tandem fish is small enough.In addition,the results also show that high propulsive efficiency does not mean high energy-saving efficiency.The energy-saving effect of the anti-phase case is more remarkable than that of the in-phase case.The average energy-saving efficiency of the anti-phase case is as high as 22.4%.