摘要
用二维波动翼型模拟鳐鱼的近壁游动,分析在壁面附近波动翼产生推力的机理和调节升力的机制,以及增推效应。计算结果发现:相对于无壁面的情形,近壁面的波动翼型尾缘脱涡强度增大,且交替脱出的正向和反向涡(反向冯·卡门涡街)间距略微增加,从而增大了推力;升力的调节主要依赖翼型的仰角,随着距离壁面高度的减小,需要适当增大仰角才能使升力为零;波幅和频率的提高都增强了波动翼的壁面效应。这意味着鳐鱼贴底游动时,推力得到增强,从而提高游速,但同时也需适当增大身体的仰角来维持与壁面的距离不变。
An undulating two-dimensional airfoil model is used to model the batoid fish swimming near a flat ground. The mechanisms of the thrust generation and its enhancement near the ground are investigated by using the vorticity dynamics theories. The lift-tuning way is found to satisfy the zerolift when undulating airfoil is near the ground. The results show that,when the undulating airfoil is near the ground,the strength of the alternated vortices shedding from the trailing edge is enhanced and the distance between the two raws of vortices（ reverse von Krmn vortex street） increases slightly. These two factors cause enhancement of the thrust. The lift adjustment relies on the angle of attack. The smaller distance between the airfoil and the ground,the bigger angle of attack is required to adjust the lift to zero. Furthermore,the ground effect（ thrust increase） is enhanced by increasing amplitude and frequency of the undulating airfoil. The present study indicates that a batoid fish gains stronger thrust when it swims closer to a ground,but it should increase its angle of attack to maintain the distance to the ground.
出处
《中国科学院大学学报（中英文）》
CSCD
北大核心
2017年第1期23-31,共9页
Journal of University of Chinese Academy of Sciences
基金
国家自然科学基金(11372310)资助
