High temperature gradient wall shear stress micro-sensors for flow separation control
Résumé
This paper reports CMOS-compatible calorimetric micro-sensors enabling the bidirectional measurement of wall shear stress in aerodynamic flows. Measuring both the amplitude and the sign of the wall shear stress at small length-scale and high frequencies, the micro-sensors are particularly suitable for flow separation detection and flow control. Their design is hot-wire like with three parallel micro wires suspended over a micro-cavity and mechanically supported using periodic perpendicular micro-bridges. The micro-sensors were manufactured using microelectronics techniques. Implemented on a flexible packaging, the micro-sensors were calibrated in static and in dynamic, in flat plate configuration, inside a turbulent boundary layer wind tunnel. After calibration, twelve micro-sensors have been implemented in a flap model for active flow control experiments. The work included the design and manufacturing of appropriate miniaturized electronics. The micro-sensors successfully detected the natural flow separation. The efficiency of the active flow control for avoiding separation or reattaching a separated flow was also evaluated in this configuration using the micro-sensors.
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