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Avi Seifert with Tel - Aviv University |
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Date: August 4, 2004
Time: 10:00am
Location: NIA, Rm 404
Speaker: Avi Seifert with Tel-Aviv University
Subject:* "Centennial of Wright Stuff: Abbreviated Technological View of Flight, Boundary Layer and Flow Control Research (History, Present and Outlook)"
Today’s airplanes fly faster, higher and for longer distances than ever before. Modern airplanes are large and safe, are economical, comfortable and computer controlled. However, the aerodynamic functionality is disappointingly similar to that of the Wright Flyer, 100 years ago. The three major flight systems are considered separately: the wings, control surfaces and engines provide the lift, flight control and thrust, respectively. The introduction of the boundary layer concept and its control, by Ludwig Prandtl in 1904, allowed gradual improvements in efficiency of fluid related systems. Celebrating 100 years of flight and powered flow control is an opportunity to look back, reflect on what was achieved and wonder where should we progress.
It is highly desirable to combine the three major systems needed to maintain flight into a single multifunctional system that will be real-time configurable. Using active flow control, this high task is achievable, but significant obstacles remain. The state-of-the-art and especially the remaining challenges will be discussed in the context of Miniature Aerial Vehicles (MAV). To enable such a technological leap, significant progress should be made in areas such as computational fluid mechanics, structures, smart materials, actuators and sensors, control theory, energy storage and more.
The 1.5 hours long talk will also present the upcoming talk at the IUTAM symposium ”100 years of boundary layer research” (11-14 Aug, Goettingen, Germany, co-authored by LaTunia Pack-Melton of NASA Langley) honoring 100 years to Prandtl’s pioneering lecture. The lecture is entitled: “Control and Identification of Turbulent Boundary Layer Separation”. Its abstract follows.
Effective delay of turbulent boundary layer separation could be achieved via closed-loop control. Constructing such a system requires that sensor data be processed, real-time, and fed into the controller to determine the output. Current methods for detecting turbulent boundary layer separation are lacking the capability of localized, fast and reliable identification of the boundary layer state. A method is proposed for FFT processing of time series, measured by hot-film sensors, with the purpose of identifying the alternation of the balance between small and large scales as the boundary layer separates, favoring the large scales. The method has been validated by comparison to other criteria of separation detection and over a range of baseline and controlled flow conditions on a “simplified” high-lift system, incorporating active flow control.
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