并列仿生鱼自主游动的数值模拟研究

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

采用自适应浸没边界方法,数值模拟了两条并列仿生鱼在不同间距下的同相位和反相位自主游动。通过与相同游动参数下单条仿生鱼自主游动的比较,可以得到结论:(1)并列自主游动的速度小于单条鱼游动的速度,并且随着间距减小而减小。相同间距下,反相位并列游动时的速度大于同相位;(2)并列游动时的阻力均大于单条鱼,且随着间距减小而增大;(3)反相位游动时功率消耗随间距减小而增大,但同相位游动则相反;(4)当间距大于0.5个身长时,推进效率都略有增大。所以,在综合考虑了游动速度和推进效率两方面的因素后认为,鱼群中并列相邻的两条鱼应当以反相位摆动,且侧向间距保持在0.5个身长以上,这与自然界中观察的结果是一致的。

Numerical simulations of two self-propelled fish in a side-by-side arrangement has been numeri- cally investigated using an adaptive version of immersed boundary method. Two typical cases of the phase difference between the adjacent fish, i. e. , in-phase and anti-phase self-propelled swimming, are considered. Compared with the performance of a single self-propelled fish swimming, the results show that：（1） the swimming speed of fish school is smaller than that of an individual fish, and decrease as the lateral distance decrease,and that of the anti-phase case is bigger than that of the in-phase case with the same lateral distance; （2） the drag of fish school is bigger than that of an individual fish,and increases as the lateral distance decreases; （3） the power consumption of the anti-phase case increases as the lateral distance decreases,which is opposite to that of the in-phase case; （4） the propulsive efficiency increases slightly when the lateral distance is bigger than 0.5L （L is the fish body length）. Therefore, with the consideration of the swimming speed and the propulsive efficiency,two side-by-side arranged fish should beat their tails in anti-phase and the lateral distance should be bigger than 0.5L, which is consistent with the observations in nature.