Reactive mixing in swirling flows

The effect of swirl on the mixing of two gas streams of the same density and axial velocity in a coaxial annular geometry has been examined. The flow is studied via a fluorescent tracer, 2-3 biacetyl. Through direct excitation, collisional excitation, and collisional de-excitation of the tracer, the turbulent transport, molecularly mixed and unmixed regions in the flow are visualized. The visualization results indicate that there are interesting three dimensional inviscid large scale structures. Mixing in the molecular level is found to be mainly localized in these structures.