Study on the influence of vibration obstacle type on the hydrodynamic performance of flapping caudal fin
Based on computational fluid dynamics(CFD)methods combined with Fluent's dynamic mesh technology,the hydrodynamic performance of a flapping caudal fin in its wake fields generated by different vibration obstacles was studied.The average thrust coefficient,power consumption and propulsion efficiency of the flapping caudal fin were obtained by changing the distance between the leading edge of the caudal fin and the center point of the obstacle(S),the size of the obstacle(d)and the incoming flow velocity(U),and the analysis was conducted based on the pressure distribution contour and vortex contour of the flow field.The calculation results show that the presence of obstacles can improve the propulsion performance of the flapping caudal fin.Under fixed S,d and U,the maximum average thrust and maximum propulsion efficiency of the flapping caudal fin in the wakes of a vibrating square cylinder were higher than its maximum average thrust and maximum efficiency in the wakes of a vibrating D-shaped cylinder and cylinder wake.When the obstacles are of a D-shaped cylinder,cylinder and square cylinder,the vortex of the opposite D-shaped cylinder,cylindrical vortex and square cylinder vortex and the leading edge vortex of the caudal fin produce an extrusion effect to increase the strength of the leading edge vortex of the caudal fin.
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