翼型局部弹性自激振动的增升减阻效应研究

Numerical Analysis of Lift Enhancement and Drag Reduction by Self-Induced Vibration of Localized Elastic Airfoil

基于几何非线性的浅拱理论及空气动力学理论,建立了局部弹性翼型的气动弹性模型,并针对该模型建立了在ALE坐标下局部弹性翼型与非定常流场的耦合算法;对振动NACA0012翼型的非定常气动力进行了计算,结果与文献数据吻合良好,验证了算法的准确性;对雷诺数为2×105时弹性翼面自激振动对翼型的增升减阻效应进行了数值分析.研究结果表明,同刚性翼型的气动特性相比,翼型的局部弹性自激振动使翼型的气动特性得到了明显改善:其失速角度从原来的13°推迟到了16°;在大攻角下,翼型的升阻比提高了80%以上.频谱分析发现:在攻角为8°和11°时,翼面振动与流场的耦合出现同步现象;在攻角为16°时,翼型的局部自激振动使剪切层内形成一系列小尺度涡,同时削减了大涡的尺寸,这使得升、阻力的波动幅度减小,在一定程度上改善了翼型的气动性能.文中建立的气弹模型具有明显的减阻增升效果,可望应用于翼型的优化设计.

The effect of the self-induced vibration of a localized elastic airfoil on the aerodynamic performance of the airfoil at Reynolds number=2×105 is studied numerically.In particular,the influence on the lift enhancement and drag reduction of the airfoil is analyzed.An aero-elastic model of the localized elastic airfoil is established following the theory of shallow arch with geometric nonlinearity and aerodynamics,and an algorithm for the aero-elastic model is developed under the ALE framework.Furthermore,the case of unsteady flow around oscillating NACA0012 airfoil is simulated via the presented algorithm,and the lift coefficients are in good agreement with the data from the literature,which verifies the accuracy and feasibility of the algorithm for unsteady flow.The effect of the self-induced vibration of the structure on aerodynamic performance of the airfoil is investigated numerically.The results show that the aerodynamic performance of the localized elastic airfoil is improved greatly compared with the rigid airfoil.The stall angle is delayed from 13° to 16° and the lift-to-drag ratio increases by more than 80% due to the self-induced vibration of the localized elastic airfoil.Adopting FFT analysis,the synchronization between the vibration of the airfoil and the evolution of the unsteady flow occurs at the attack angles of 8° and 11°,respectively.As the attack angle is 16°,a series of small-sized vortices is formed in the shear layer and the size of the large eddy is decreased,which reduces the fluctuation amplitude of the lift and drag significantly and improves the aerodynamic performance accordingly.