摘要
本研究数值模拟了狭窄通道内的三维自推进鱼体游动,其中鱼体摆动方向与上下壁面平行.研究发现,在相同雷诺数(Re)下,随着通道变窄(上下壁面间隙减小),鱼体游速增快,功耗降低.在较高雷诺数(Re=2600)下,本研究的壁面间隙范围内,功耗始终低于自由游动,而在较低雷诺数(Re=410)下与自由游动功耗相比,存在不同的间隙区间.进一步研究了Re数的影响,结果表明,相同通道高度下,随着Re数降低,鱼体游速降低,但始终高于自由游动,鱼体功耗提高,但始终低于自由游动.最后,为了探究其中的物理机制,分析了鱼体产生的涡旋结构和涡量场,发现壁面效应提高了尾流射流强度,从而增大游速和降低功耗.相反地,Re数下降导致尾流射流强度下降和模式改变,从而减小游速和提高功耗.
Abstract
In this study,a three-dimensional simulation of a fish-like body swimming in a narrow channel with non-slip walls is carried out using the immersed boundary method.The fluctuation direction of the body is parallel to the walls.The results show that at the same Reynolds number,as the channel becomes narrower(i.e.,the distance between the upper and lower walls decreases),the swimming speed of the fish-like body increases while its power consumption decreases.At a higher Reynolds number(Re=2600),the power consumption is consistently lower than that of free swimming within the range of wall distances studied.However,at a lower Reynolds number(Re=410),there are distinct zones compared to free swimming.Furthermore,the effect of the Reynolds number is investigated.At the same channel height,as the Reynolds number decreases,the swimming speed of the fish-like body decreases but remains higher than that of free swimming,and its power consumption increases but stays lower than that of free swimming.Finally,to explore the underlying physical mechanisms,we analyze the vortex structures and vorticity field generated by the fish-like body.We find that the wall effect enhances the intensity of the wake jet,resulting in increased swimming speed and decreased power consumption.Conversely,a reduction in the Reynolds number leads to a decrease in the intensity of the wake jet and a change in its mode,which reduces the swimming speed and increases the power consumption of the fish-like body.
维普
万方数据