CAJ | 학술논문

基于Navier-Stokes方程的数值解，研究了一模型昆虫翼在小雷诺数(Re=100)下作非定常运动时的气动力特性.这些运动包括：翼启动后的常速转动，快速加、减速转动，常速转动中快速上仰(模拟昆虫翼的上挥或下拍、翻转等运动).有如下结果：在小雷诺数下，模型昆虫翼以大攻角(α=35°)作常速转动运动时，由于失速涡不脱落，可产生较大的升力系数.其机理是：翼转动时，翼尖附近(该处线速度大)上翼面压强比翼根附近(该处线速度小)的小得多，因而存在展向压强梯度，同时存在着沿展向的离心力，此展向压强梯度和离心力导致的展向流动在失速涡的轴向方向，其可避免失速涡脱落.模型昆虫翼在快速加、减速转动和快速上仰运动中，虽然雷诺数小，但由于在短时间内产生了大涡量，也可产生十分大的气动力，例如在快速上仰运动中，升力系数可大于10.
기우Navier-Stokes방정적수치해，연구료일모형곤충익재소뢰낙수(Re=100)하작비정상운동시적기동력특성.저사운동포괄：익계동후적상속전동，쾌속가、감속전동，상속전동중쾌속상앙(모의곤충익적상휘혹하박、번전등운동).유여하결과：재소뢰낙수하，모형곤충익이대공각(α=35°)작상속전동운동시，유우실속와불탈락，가산생교대적승력계수.기궤리시：익전동시，익첨부근(해처선속도대)상익면압강비익근부근(해처선속도소)적소득다，인이존재전향압강제도，동시존재착연전향적리심력，차전향압강제도화리심력도치적전향류동재실속와적축향방향，기가피면실속와탈락.모형곤충익재쾌속가、감속전동화쾌속상앙운동중，수연뢰낙수소，단유우재단시간내산생료대와량，야가산생십분대적기동력，례여재쾌속상앙운동중，승력계수가대우10.
The aerodynamic forces and flow structures of a wing of relatively small, aspect ratio in some unsteady rotational motions at low Reynolds number (Re = 100) are studied by numerically solving the Navier-Stokes equations. These motions include wing in constant-speed rotation after a fast start, wing accelerating and decelerating from one rotational speed to another,and wing rapidly pitching-up in constant-speed rotation. When a wing performing constant-speed rotation at small Reynolds number after started from rest at large angle of attack (α = 35°), a large lift coefficient can be maintained. The mechanism for the large lift coefficient is that for a rotating wing, the variation of the relative velocity along the wing-span causes a pressure gradient,centrifugal force also exists and hence a spanwise flow which can prevent the dynamic stall vortex from shedding. When a wing rapidly accelerating or decelerating from one rotational speed to another, or rapidly pitching-up during constant-speed rotation, even if the aspect ratio of the wing is small and the flow Reynolds number is low, large aerodynamic force can be obtained. During these rapid unsteady motions, new layers of strong vorticity are formed near the wing surfaces in very short time, resulting large time rate of change of the fluid impulse which is responsible for the generation of large aerodynamic force.