低雷诺数翼型局部振动非定常气动特性

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。

Unsteady aerodynamic characteristics of airfoil with local oscillation at low Reynolds number

The unsteady numerical simulation method based on the dynamic mesh is used to study the effects of skin oscillation at different locations and with different frequencies and amplitudes on the aerodynamic characteristics and flow field structures of the airfoil at low Reynolds number, and reveal the mechanism of lift augmentation and drag reduction. The research shows that the local oscillation of the airfoil surface can improve the aerodynamic characteristics of the airfoil at low Reynolds number. Compared with that of the rigid airfoil, local oscillation of the airfoil surface can improve the lift coefficient, reduce the drag coefficient and improve the lift to drag ratio of the airfoil. Locations of oscillation have significant effects on the aerodynamic characteristics and flow field structures of the airfoil. When the oscillation surface is at the leading edge or the center of the laminar separation bubble, oscillation can control the laminar separation of the airfoil effectively, so the aerodynamic characteristics of the airfoil are improved. Frequencies of oscillation have significant effects on locations of laminar separation and transition of the airfoil. With the increase of the frequency, the aerodynamic characteristics of the airfoil have the optimal value. Compared with the rigid airfoil, oscillation makes the transition move upstream and the viscous drag increased, but makes the equivalent relative thickness of the airfoil decreased and the pressure drag reduced observably. In the range of small amplitudes, with the increase of the amplitude, the unsteady characteristics are more significant and the lift to drag ratio increases.