46th AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV, United States Of America, 7 - 10 January 2008
The data from unforced and open loop forced simulations of the wake behind an axisymmetric bluff body at ReD=1,500 is analyzed to explore the effect of forcing. In the unforced wake, because of the axial symmetry of the body, structures do not maintain a constant azimuthal phase over time, which leads to inaccurate predictions of the flow field when applying POD. Forcing inside the "lock-in" region in amplitude-frequency space with a fixed azimuthal phase is therefore introduced to study the wake in detail. The resulting flow field is analyzed using three methods, namely an azimuthal Fourier transform, a moment of inertia calculation, and a velocity vector histogram, to determine the azimuthal phase of the wake structures. The overall goal is to minimize the necessary data volume to analyze the flow for eventual implementation in real time feedback flow control experiments. It is shown that the methods used to determine the azimuthal phase all yield a measure of the phase angle of the symmetry plane in the wake.