A computational study of the aerodynamic forces and power requirements of dragonfly (Aeschna juncea) hovering
A computational study of the aerodynamic forces and power requirements of dragonfly (Aeschna juncea) hovering
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DOI：
10.1242/jeb.00969
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发表时间：
2004-05-01
影响因子：
2.8
通讯作者：
Lan, SL
中科院分区：
文献类型：
--
作者：
Sun, M;Lan, SL
研究了蜻蜓（Aeschna juncea）悬停飞行时的气动力产生和机械功率需求。采用数值求解移动重叠网格中纳维-斯托克斯方程的方法。当下冲程和上冲程的中冲程攻角分别设置为52度和8度时（这些值接近观测值），平均垂直力等于昆虫重量，平均推力近似为零。在一个扑动周期中有两个较大的垂直力峰值。一是在周期的前半段，这主要是由于后翼的下划动作；另一个是在周期的后半段，这主要是由于前翼处于下冲程。蜻蜓以大的冲程平面角度（52度）悬停，以阻力作为其重量支撑力的主要来源（总垂直力的大约65％由阻力贡献，35％由翅膀的升力贡献）。翅膀的垂直力系数是准稳定值的两倍。前翼和后翼之间的相互作用不是很强，不利于垂直力的产生。与单翼相同运动的情况相比，相互作用效应使前翼和后翼的垂直力分别减少了相应单翼的14%和16%。较大的垂直力是由于非定常流动效应造成的。非定常力的产生机制是，后翼或前翼每次下冲时，都会产生一个新的包含向下动量的涡环，产生向上的力。体重比功率为37 W kg(-1)，主要由空气动力贡献。
Aerodynamic force generation and mechanical power requirements of a dragonfly (Aeschna juncea) in hovering flight are studied. The method of numerically solving the Navier-Stokes equations in moving overset grids is used.When the midstroke angles of attack in the downstroke and the upstroke are set to 52degrees and 8degrees, respectively (these values are close to those observed), the mean vertical force equals the insect weight, and the mean thrust is approximately zero. There are two large vertical force peaks in one flapping cycle. One is in the first half of the cycle, which is mainly due to the hindwings in their downstroke; the other is in the second half of the cycle, which is mainly due to the forewings in their downstroke. Hovering with a large stroke plane angle (52degrees), the dragonfly uses drag as a major source for its weight-supporting force (approximately 65% of the total vertical force is contributed by the drag and 35% by the lift of the wings).The vertical force coefficient of a wing is twice as large as the quasi-steady value. The interaction between the fore- and hindwings is not very strong and is detrimental to the vertical force generation. Compared with the case of a single wing in the same motion, the interaction effect reduces the vertical forces on the fore- and hindwings by 14% and 16%, respectively, of that of the corresponding single wing. The large vertical force is due to the unsteady flow effects. The mechanism of the unsteady force is that in each downstroke of the hindwing or the forewing, a new vortex ring containing downward momentum is generated, giving an upward force.The body-mass-specific power is 37 W kg(-1), which is mainly contributed by the aerodynamic power.