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Synchronized force and particle image velocimetry measurements on a NACA 0015 in post stall under control of time periodic electromagnetic forcing
Cierpka, C.; Weier, T.; Gerbeth, G.;
The paper shows the results of an experimental investigation of flow control by periodic actuation by streamwise Lorentz forces at the leading edge of a NACA0015 profile. Synchronized force and time resolved particle image velocimetry (PIV) measurements were performed in a sodium hydroxide channel for Reynolds numbers of Re = 0.5 105 and 105. A wavelet algorithm was used to detect vortical structures and allows to relate these large scale structures to the observed lift and drag forces. Additional information about the mechanism of momentum transfer in the flow was gained by proper orthogonal decomposition of the data. In order to minimize the energetic effort of the flow actuation, the investigation focuses on small momentum coefficients. For small angles of attack a complete reattachment of the flow can be established by the actuation, whereas for large angles of attack the interaction of vortical structures becomes more prominent. The paper discusses the effects of excitation frequency and wave form for two qualitatively different flow regimes .It shows that the proper choice of the excitation frequency is very important for large angles of attack. The optimal excitation frequency was examined as a function of the angle of attack.
Keywords: active flow control, Lorentz force, flow separation

Publ.-Id: 13393 - Permalink