University of Notre Dame, Institute for Flow Physics and Control, Hessert Laboratory for Aerospace Research, Notre Dame, IN 46556, USA.
Philos Trans A Math Phys Eng Sci. 2011 Apr 13;369(1940):1459-75. doi: 10.1098/rsta.2010.0356.
Single dielectric barrier discharge plasma actuators have been used to control flow separation in a large number of applications. An often used configuration involves spanwise-oriented asymmetric electrodes that are arranged to induce a tangential wall jet in the mean flow direction. For the best effect, the plasma actuator is placed just upstream of where the flow separation will occur. This approach is generally more effective when the plasma actuator is periodically pulsed at a frequency that scales with the streamwise length of the separation zone and the free-stream velocity. The optimum frequency produces two coherent spanwise vortices within the separation zone. It has been recently shown that this periodic pulsing of the plasma actuator could be sensed by a surface pressure sensor only when the boundary layer was about to separate, and therefore could provide a flow separation indicator that could be used for feedback control. The paper demonstrates this approach on an aerofoil that is slowly increasing its angle of attack, and on a sinusoidally pitching aerofoil undergoing dynamic stall. Short-time spectral analysis of time series from a static pressure sensor on the aerofoil is used to determine the separation state that ranges from attached, to imminent separation, to fully separated. A feedback control approach is then proposed, and demonstrated on the aerofoil with the slow angle of attack motion.
单个介电阻挡放电等离子体激励器已被用于控制大量应用中的流动分离。一种常用的配置涉及沿展向取向的非对称电极，这些电极被布置为在平均流动方向上诱导切向壁射流。为了达到最佳效果，等离子体激励器应放置在流动分离即将发生的上游位置。当等离子体激励器以与分离区流向长度和自由流速度成比例的频率周期性脉冲时，这种方法通常更有效。最佳频率会在分离区内产生两个相干的展向涡。最近已经表明，只有当边界层即将分离时，表面压力传感器才能感受到等离子体激励器的这种周期性脉冲，因此它可以提供一种流动分离指示器，可用于反馈控制。本文在缓慢增加攻角的翼型和经历动态失速的正弦俯仰翼型上演示了这种方法。使用翼型上静态压力传感器的时间序列的短时谱分析来确定分离状态，范围从附着到即将分离到完全分离。然后提出了一种反馈控制方法，并在具有缓慢攻角运动的翼型上进行了演示。
