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Within the scope of the Collaborative Research Centre SFB 557 "Control of Complex Turbulent Shear Flows" at TU Berlin this project deals with the reduction of the total drag of generic three-dimensional car models (Ahmed body) by means of Active Flow Control (AFC). The highly complex wake region behind these models consists of steady longitudinal vortices occuring at the outer slant edges depending on the slant angle and unsteady lateral vortex structures occurring at the upper and lower edge of the base between the longitudinal structures. During the experiments these vortex structures were influenced by different actuation concepts using steady- and periodic-blowing compressed-air jets. Avariation of the forcing intensity and frequency (Strouhal number) showed a strong influence of these parameters on the effectiveness of the actuation. The isolated use of the different actuation concepts leads to a drag reduction of up to 5.6% (steady blowing) or 5.1% respectively (periodic-blowing slot). The combination of the two actuation concepts enables a drag reduction of up to 7.1% and an increase in base pressure of up to 15.5%. An extremum-seeking feedback controller was used to exploit the full AFC benefits, e. g. the controller adjusts the optimal actuation parameters, such that the total drag is minimized.

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International Journal of Flow Control

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