POD Analysis of 3-D Flow Visualization Images of an Acoustically Excited Jet
نویسندگان
چکیده
A three-dimensional (3-D) modal analysis of an excited circular jet with Reynolds number of 9500 is conducted using proper orthogonal decomposition (POD) and a highspeed 3-D flow visualization system. Large sets of 3-D data are acquired in the near field before the end of the potential core and the transition region of the jet. POD is used to objectively characterize and classify the 3-D images and elucidate the fundamental structure of the flow. As expected, the near field of the jet is dominated by the formation and growth of ring vortices, which is also reflected in the shape of the POD modes. The onset of azimuthal instabilities is also clear in the instantaneous 3-D images, which show long streamwise fingers, or side jets, of fluid surrounding the vortex rings. The results presented here show the strength of 3-D modal analysis for understanding the most dominant structures and instabilities in the jet.
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