仿生蓝点魟胸鳍在两种波动模式下推进力的比较

Comparative Analysis of Thrust Generation of Biomimetic Bluespotted Stingray Pectoral Fin under Two Undulating Propulsion Patterns

依靠鱼鳍波动推进的鱼类通常具备极强的游动稳定性和机动性能,在这些鱼类中,根据鱼鳍波状运动形成行波波幅包络线形式的不同,鱼鳍波动模式主要有摆幅从前往后逐渐增大和摆幅保持不变两种。设计出一种仿生蓝点魟胸鳍模型,通过试验研究模型在两种波动模式下频率、摆幅和波长等运动学参数对产生推进力大小的差异。测试结果显示,在两种波动模式下,推进力基本上随着波动频率、摆幅和波长的增大而增加;在相同运动学参数下,摆幅逐渐增大模式产生的推进力始终大于等摆幅模式;为进一步深入研究并揭示其中的缘由,随后建立仿生蓝点魟胸鳍的二维模型,利用有限体积法对建立的模型及计算域进行离散,基于流体动力学对两种波动模式下仿生鳍推进力进行计算,给出与试验条件相似的运动学参数下鱼鳍在两种波动模式下推进力大小随之变化情况的数值计算结果,绘制出压力分布等值线图和涡量场分布情况,并从涡动力学角度解释试验现象和揭示其原理及内在规律。该研究成果为仿生蓝点魟胸鳍选择合理的推进模式,高效、可靠地完成预定任务提供理论参考。

Fishes that rely on fin undulating motion to propel themselves usually have an extraordinary stability and maneuvering.Among them,the propulsion patterns are generally divided into two types according to the amplitude envelop formation of travelling wave,i.e.amplitude gradually increases from anterior to posterior and amplitude that stay consistent along the fin.A biomimetic pectoral fin of bluespotted ray is developed,and an experiment is implemented to investigate the differences of thrust between the two propulsion patterns under different undulating frequency,amplitude and wavelength.The experimental results illustrate that the propulsion thrust mainly increases with the increase of undulating frequency,amplitude and wavelength under both propulsion patterns.However,the thrust generated under the pattern with amplitude gradually increases from anterior to posterior is always larger than the one generated under the pattern with amplitude that stay consistent along the fin under the same kinematic parameters.Thus,for a further investigation to the experiment observations,a two dimensional biomimetic pectoral fin model is established.By taking advantage of finite volume method（FVM）,the model and its corresponding computational region were dissociated.Then,the propulsion thrust of the two patterns is calculated based on computational fluid dynamic（CFD）.A comparative analysis of thrust generation under different frequency,amplitude and wavelength is carried out.Finally,the pressure contour and vortex distribution in the wake of the fin is illustrated.The current findings are used for propulsion pattern selection of biomimetic fin to achieve efficient and reliable application.