幼鱼体长差异性对群游推进效率的影响研究

Study on the free swimming mechanical characteristics of juvenile grass fishes based on vorticity analysis

为探究上下游鱼之间的体长差异性对鱼群群游效率的影响,本文基于Fluent动网格技术,对幼鱼鱼群稳定游动状态下的鱼体周身涡量和推进效率等进行了数值模拟分析。计算结果表明,群游幼鱼的推进效率相比单尾鱼最高可提升5%,上游鱼体长大于下游鱼体长(ΔL>0 cm)时,随体长差异的增大,鱼群尾流结构(d/D)增大,整体推进效率减小;上游鱼体长小于下游鱼体长(ΔL<0 cm)时,随体长差异的增大,鱼群尾流结构(d/D)和整体推进效率减小。当上下游幼鱼的体长差ΔL=0.5 cm时,三角形组合的鱼群整体推力系数和功率系数最高分别可达5.11×10^(-3)和1.71×10^(-3),该组合下的整体推进效率可达17.2%。

In order to explore the impact of the difference in body length between the upstream and downstream fish on the efficiency of the fish school,the vorticity and propulsion efficiency of the fish body under the stable swimming state of the juvenile fish school are analyzed in this paper is based on the Fluent dynamic grid technology.A numerical simulation is carried out.The calculation results show that the propulsion efficiency of shoal juveniles can be increased by up to 5%compared with single-tailed fish.When the body length of the upstream fish is greater than the body length of the downstream fishΔL>0 cm,the difference of body length increases with the increase of the fish wake structure(d/D)increases,the overall propulsion efficiency decreases;when the upstream fish body length is smaller than the downstream fish body lengthΔL<0 cm,the fish school wake structure(d/D)and overall propulsion efficiency decrease with the increase of the body length difference.When the body length difference between the upstream and downstream juveniles isΔL=0.5 cm,the overall thrust coefficient and power coefficient of the triangle combination can reach 5.11×10^(-3) and 1.71×10^(-3),respectively.The overall propulsion efficiency under this combination can reach 17.2%.