Coherent structure eduction from PIV data of an electromagnetically forced separated flow

Periodic addition of momentum by wall–parallel electromagnetic forces has a strong influence on the separated region of a stalled airfoil. As in the case of periodic blowing and suction, actuation frequency and momentum input are the main factors of influence. However, the control authority depends as well on the actuation wave form. This latter aspect is investigated in the present paper by means of time resolved particle image velocimetry data from the suction side of an inclined flat plate. The control effect is rated by the size of the remaining recirculation region in the time averaged flow fields. The controlled flow possesses typically a small number of relatively large vortices, which are believed to be related to the control mechanism. Consequently, the time resolved flow fields have been analyzed by proper orthogonal decomposition and continuous wavelet transform to extract dominant features of the flow.