低雷诺数下翼型分离流动抽吸控制特性研究

Investigation on characteristics of suction control on separation flow around an airfoil at low Reynolds number

为了系统研究抽吸系数和抽吸方向对抽吸效果的影响以及抽吸效益与抽吸能耗之间的关系,以NACA0012翼型表面分离流动为基准状态,在其吸力面设计了局部多孔抽吸结构,采用Roe格式和双时间步隐式算法(LUSGS),从抽吸系数、抽吸方向和抽吸能耗等方面,数值研究了低雷诺数下多孔分布式抽吸结构对流动分离的控制效果,通过边界层速度线型的变化分析了抽吸控制机理。研究结果表明:在翼型吸力面流动分离点附近一定区域内进行抽吸,可有效抑制流动分离,改善翼型气动性能;随着抽吸系数的增加,升阻比先是快速增长然后缓慢下降,且升阻比最大值提高了约1.3倍。抽吸控制能量消耗评估显示抽吸系数在合理范围内时,控制能耗明显小于控制效益。抽吸角度对抽吸控制有显著影响,当抽吸角度较大时,不仅翼型升阻比获得了提升,而且抽吸控制所消耗的能量也会进一步减少。这些结果有助于进一步为流动控制设计提供新的思路和方法。

In order to research the effect of suction coefficients and directions on suction control,and the relationship between effectiveness and cost of suction,a local suction distribution on the upper surface of the NACA0012 airfoil is designed to control the flow separation.The effectiveness of the designed suction distribution is investigated numerically using Roe scheme and LU-SGS implicit scheme with dual-time-stepping technique.The mechanism of suction con-trol is analyzed by comparing the velocity profiles in the boundary layer.The penalty for utilizing suction control is also estimated.The computational results show that the designed suction distri-bution is capable of suppressing the flow separations and improving the aerodynamic perform-ances.With the increase of the suction coefficients,the lift-to-drag ratio increases fast firstly and then decrease slowly,while the maximum increase is about 130%.The analysis of energy consumption shows that the cost for using suction to suppress separation flow is relatively small with an appropriate suction coefficient.The effect of suction angles on suction control is obvious. As the suction angle becomes larger,not only the lift-to-drag ratio increases,but also the cost of suction decreases.These results will further help to provide new ideas and methods for flow control design.