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Boundary Layer Separation and Reattachment Detection on Airfoils by Thermal Flow Sensors
IMSAS (Institute for Microsensors, -actuators and -systems), MCB (Microsystems Center Bremen), University of Bremen, Otto-Hahn-Allee, Bldg. NW1, 28359 Bremen, Germany
Deutsche Wind Guard Wind Tunnel Services GmbH, Oldenburger Straße 65, 26316 Varel, Germany
* Author to whom correspondence should be addressed.
Received: 30 August 2012; in revised form: 16 October 2012 / Accepted: 18 October 2012 / Published: 24 October 2012
Abstract: A sensor concept for detection of boundary layer separation (flow separation, stall) and reattachment on airfoils is introduced in this paper. Boundary layer separation and reattachment are phenomena of fluid mechanics showing characteristics of extinction and even inversion of the flow velocity on an overflowed surface. The flow sensor used in this work is able to measure the flow velocity in terms of direction and quantity at the sensor’s position and expected to determine those specific flow conditions. Therefore, an array of thermal flow sensors has been integrated (flush-mounted) on an airfoil and placed in a wind tunnel for measurement. Sensor signals have been recorded at different wind speeds and angles of attack for different positions on the airfoil. The sensors used here are based on the change of temperature distribution on a membrane (calorimetric principle). Thermopiles are used as temperature sensors in this approach offering a baseline free sensor signal, which is favorable for measurements at zero flow. Measurement results show clear separation points (zero flow) and even negative flow values (back flow) for all sensor positions. In addition to standard silicon-based flow sensors, a polymer-based flexible approach has been tested showing similar results.
Keywords: boundary layer separation; flow separation; stall; reattachment; airfoil; wind tunnel; thermal flow sensor; flexible; polyimide; thermopile
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Sturm, H.; Dumstorff, G.; Busche, P.; Westermann, D.; Lang, W. Boundary Layer Separation and Reattachment Detection on Airfoils by Thermal Flow Sensors. Sensors 2012, 12, 14292-14306.
Sturm H, Dumstorff G, Busche P, Westermann D, Lang W. Boundary Layer Separation and Reattachment Detection on Airfoils by Thermal Flow Sensors. Sensors. 2012; 12(11):14292-14306.
Sturm, Hannes; Dumstorff, Gerrit; Busche, Peter; Westermann, Dieter; Lang, Walter. 2012. "Boundary Layer Separation and Reattachment Detection on Airfoils by Thermal Flow Sensors." Sensors 12, no. 11: 14292-14306.