压力-行为耦合下鱼类波动推进机理研究

Fluctuation swimming is a common swimming mode among most aquatic organism. And the existing fluctuation model cannot reflect the dynamics characteristics of fluctuation swimming of fish comprehensively, because the model neglects the feedback effects of pressure and pressure gradient on the parameters of fluctuation..So the test of swimming behavior for juvenile grass carp and juvenile bighead carp will be made to study the influence rule of pressure and pressure gradients to the amplitude and frequency of fluctuation, and the coupling interactions between pressure and fish undulation behavior will be investigated as well, then an undulation swimming model is established for the juvenile grass carp and juvenile bighead carp. .Undulation swimming dynamical model is embedded in the flexible body deforming theory to realize the simulation of undulating propulsion process of fish under the coupling of pressure and behavior. .The undulating propulsion mechanism of fish will be revealed by combining the coupling analysis system with fish behavior theory, and the key hydraulic factors beneficial to generation of swimming impetus will be explored to build the fishway evaluation model of hydraulic parameters based on the mechanism of swimming impetus. The research results can provide scientific basis for the research of key technical issues of swimming behavior, and theoretical support for the hydraulic evaluation indicator.

波动游动是很多水生生物采用的游动方式。已有的波动模型忽略了流场压力和压力梯度对鱼体波动参数的反馈作用，不能完全体现鱼类波动游动过程中的动力学特征。本项目将基于草鱼和鳙鱼幼鱼的游泳行为试验，研究压力和鱼类波动行为的相互耦合作用以及流场压力、压力梯度对鱼体波动幅度和波动频率的影响规律，构建适用于草鱼和鳙鱼幼鱼的波动游泳模型；将鱼体波动游泳动力学模型嵌入至柔性体变形理论，采用动网格模型实现鱼体压力-行为耦合下的波状推进过程跟踪模拟；结合压力-行为耦合分析系统和鱼类行为学理论，揭示鱼类波动推进机理，探索有利于鱼类游泳动力形成的关键水力学指标，构建基于鱼类游泳动力机制的水力学指标评价模型。研究成果可为鱼类游泳行为关键技术问题研究提供科学依据，为水力学评价指标提供理论支撑。

波动游动是典型鲹科鱼类的一种高效推进模式，定量描述流体压力或压力梯度刺激下的鱼类游泳行为是构建真实鱼体波动模型的关键。本项目以草鱼幼鱼为研究对象，开展了基于PIV技术的幼鱼自由游泳行为试验，探究了流体压力等参数对鱼体波动幅度和波动行为的影响，构建了适用于草鱼幼鱼的波动游泳模型；在此基础上，耦合柔性体变形理论,实现了不同水流环境下幼鱼个体的波动过程数值模拟，结合涡量分析原理，研究了不同游泳模式下草鱼幼鱼的动力形成过程，探索了高效推进模式下有利于鱼类游泳动力形成的关键水力学指标及其阈值。主要研究结果如下：.(1)对于在不同水流环境游动的草鱼幼鱼，鱼体周身轮廓线上的流体压力与该点处的波动幅度呈现明显的正弦变化规律，且该规律不会因为水流流速的变化而发生改变。.(2)草鱼幼鱼直线、转弯和后退三种游泳状态下的受力分析结果表明，直线和转弯时的草鱼幼鱼尾部产生的推进力占总推进力的比例最高可达54.5%，是幼鱼游泳动力的主要来源，后退时的草鱼幼鱼则主要依靠中间部位推动鱼体前进。.(3)幼鱼的整体推进效率随着尾涡结构和头部偏角的逐渐增加近似正态分布，推进效率的实验结果表明，较小的头部偏角和涡环直径比更有利于草鱼幼鱼高效推进模式的形成。