返回Google圖書搜尋

Unsteady Flow Separation Control Over a NACA 0015 Using NS-DBD Plasma Actuators

出版	Ohio State University, 2017
URL	http://books.google.com.hk/books?id=lS1eswEACAAJ&hl=&source=gbs_api

註釋Flow field surrounding a moving body is often unsteady. This motion can be linear or rotary, but the latter will be the primary focus of this thesis. Unsteady flows are found in numerous applications, including sharp maneuvers of fixed wing aircraft, biomimetics, wind turbines, and most notably, rotorcraft. Unsteady flows cause unsteady loads on the immersed bodies. This can lead to aerodynamic flutter and mechanical failure in the body. Flow control is hypothesized to reduce the load hysteresis, and is achieved in the present work via nanosecond pulse driven dielectric barrier discharge (NS-DBD) plasma actuators. These actuators have been effective in the delay or mitigation of static stall. The flow parameters were varied by Reynolds number (Re=167,000-500,000), reduced frequency (k=0.025-0.075), and excitation Strouhal number (Ste=0-10). It was observed that the trends of Ste were similar for all combinations of Re and k, and three major conclusions were drawn. It was first observed that low Strouhal number excitation (Ste0.5) results in oscillatory aerodynamic loading in the stalled stage of dynamic stall. At high Strouhal number excitation (Ste2), this behavior is not observed, as in the static stall cases. Second, all excitation resulted in earlier flow reattachment. Lastly, it was shown that excitation resulted in reduced aerodynamic hysteresis and dynamic stall vortex strength. The decrease in the strength of the dynamic stall vortex is achieved by the formation of excited structures that bleed the leading edge vorticity prior to the ejection of the dynamic stall vortex. At sufficiently high excitation Strouhal numbers (Ste ̃10), the dynamic stall vortex was suppressed.