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Active flow control of laminar boundary layers for variable flow conditions

: Simon, B.; Nernitz, T.; Rohlfing, J.; Fischer, F.; Mayer, D.; Grundmann, S.


International journal of heat and fluid flow 56 (2015), S.344-354
ISSN: 0142-727X
ISSN: 0046-7138
Deutsche Forschungsgemeinschaft DFG
GR 3524/4-1
Fraunhofer LBF ()

This work investigates the stability of a fxLMS controller for active wave cancelation of broad-band Tollmien-Schlichting disturbances in a flat plate boundary-layer with a single DBD plasma actuator. In particular the influence of a changing free stream velocity and the resulting off-design operation of the control algorithm is analyzed up to an unstable behavior. As the main reason for unstable controller operation in the off-design case the difference between actual and predicted phase angle of the disturbances at the position of the error sensor is identified. A method for an online adjustment of the secondary-path model to different free-stream velocities is presented. Finally a wall-bounded method based on the disturbances phase speed is developed that can cope with changes of the physical secondary path not only due to changes of the free-stream velocity but also due to changes of the pressure distribution. This method enables the extension of the stable operation range of the control system significantly.