Thrust-enhancement of an undulating two-dimensional batoid-like model near a flat ground

doi:10.7523/j.issn.2095-6134.2017.01.004

Abstract

Abstract:

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 zero-lift 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 Kármán 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.

Key words: ground effects, undulating airfoil, panel methods

CLC Number:

O352

ZHU Yi, YU Yongliang. Thrust-enhancement of an undulating two-dimensional batoid-like model near a flat ground[J]. , 2017, 34(1): 23-31.

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