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针对低雷诺数翼型特殊的气动特性,采用基于动网格的非定常数值模拟方法,研究翼型表面不同弦向位置的局部蒙皮以不同频率及振幅振动时对低雷诺数翼型气动特性及流场结构的影响,揭示蒙皮振动增升减阻的机理。研究表明,在低雷诺数条件下局部蒙皮振动可有效提高翼型气动特性,与刚性翼型相比蒙皮局部振动可使翼型升力系数提高,阻力系数降低,升阻比提高。振动位置对翼型气动特性及流场结构有显著的影响,振动表面位于翼型前缘附近或位于层流分离泡中心时可有效控制翼型层流分离,从而提高翼型气动特性。振动频率对翼型表面层流分离及转捩位置均有显著的影响,随着振动频率增加,翼型气动特性出现最优值。与刚性翼型相比,表面振动使翼型转捩位置略向上游移动,摩擦阻力增加,但振动使等效翼型相对厚度减小,压差阻力明显减小。在小幅振动范围内,随着振幅增加,流场非定常特性更加显著,翼型升阻比增加。
Aiming at the special aerodynamic characteristics of low Reynolds number airfoils, unsteady numerical simulation based on moving grids is used to study the aerodynamic characteristics of low Reynolds number airfoils when the local skins of different airfoil positions vibrate at different frequencies. And the influence of the flow field structure, revealing the mechanism of skin friction increasing and drag reducing. The results show that local skin vibration can effectively improve the aerodynamic characteristics of airfoil under low Reynolds number conditions. Compared with rigid airfoil, the local skin vibration can increase the lift coefficient of airfoil, reduce the drag coefficient and increase the drag ratio. Vibration position has significant influence on the aerodynamic characteristics and flow field structure of the airfoil. When the vibrational surface is near the leading edge of the airfoil or at the center of the laminar separation bubble, the aerofoil aerodynamic characteristics can be effectively controlled. Vibration frequency has a significant effect on the airfoil surface laminar flow separation and rotation position. As the vibration frequency increases, the aerodynamic characteristics of the airfoil appear optimal. Compared with the rigid airfoil, the surface vibration moves the airfoil turning position slightly upstream and increases the frictional resistance. However, the relative thickness of the equivalent airfoil decreases with the vibration, and the pressure drop resistance decreases obviously. In the small vibration range, as the amplitude increases, the unsteady flow field is more pronounced, and the lift-drag ratio increases.