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利用压力传感器测量扑翼的瞬时力,利用数字粒子测速仪(digital particle image velocimetry,DPIV)系统测量扑翼的前缘涡以及周围的流场,来揭示前缘涡在不同间距下对扑翼平均推力的影响.实验在一个低Reynolds数循环水洞中进行,两串列扑翼均做二维正弦平动.在固定的相位差下,当间距增加时,后翅前缘涡对前翅的影响具有相似性,均提高或者均降低前翅的平均推力.前翅平均推力的提高是由于后翅的前缘涡提高了前翅尾部的射流速度以及有效攻角.随着间距的增加,后翅前缘涡对前翅的影响急剧下降,使得前翅的平均推力快速接近于单翼值.在固定的相位差下,当间距增加时,前翅的脱落涡对后翅的影响变化非常大,后翅的平均推力可能先升高后降低,这是因为间距改变了前翅脱落涡作用于后翅的时间点.当前翅脱落涡遇到后翅,并且和后翅的前缘涡有相同的旋转方向时,前翅的脱落涡会抑制后翅前缘涡的形成,并且后翅的有效攻角减小,其平均推力降低.如果这两个涡的旋转方向相反,那么后翅有效攻角就会增大,平均推力值就会提高.
Using the pressure sensor to measure the instantaneous force of the flapping wing, the digital voxel velocimetry (DPIV) system was used to measure the leading edge vortex of the flapping wing and the surrounding flow field to reveal that the leading edge vortex averaged Thrust effect.The experiment is carried out in a low Reynolds circulation tunnel, and the two series of flapping wings are two-dimensional sine translation.With the fixed phase difference, when the spacing increases, the impact of the leading wing vortex on the forewing With the similarity increasing or decreasing the average thrust of the forewing.The average thrust of the forewing was increased because the leading edge eddy of the hind wing increased the jet velocity and the effective angle of attack at the tip of the forewing.With the increase of the spacing, The influence of the front wing drastically declines so that the average thrust of the front wing rapidly approaches the value of the single wing.When the spacing increases, the influence of the shedding vortex of the front wing on the hind wing greatly changes, and the average thrust of the hind wing may be First increased and then decreased because the pitch changed the time point when the forewing shedding vortex acts on the hind wing.When the current wing shedding vortex meets the hind wing and has the same direction of rotation as the leading edge vortex of the hindwing, The eddy vortex suppresses the formation of the hind wing front vortex, and the effective angle of attack of the hind wing decreases, and its average thrust decreases.If the two vortices rotate in the opposite direction, then the effective angle of attack of the hind wing increases, the average thrust The value will increase.