Characterization of large-scale structures in a forced ducted flow with dump

A forced, subsonic ducted flow with dump was studied using hot-wire anemometry. Forcing to the flow was applied by exciting the duct resonant acoustics. Flow structures (vortices) with high azimuthal coherence and high spatial and temporal periodicity were generated in the shear flow at the dump when the forcing frequency matched the first subharmonic of the initial vortex shedding frequency or the preferred mode frequency. By forcing the flow at the preferred mode frequency, mixing was enhanced in the shear-flow and pipe-flow regimes. A visual description of the coherent structures was obtained in water flow tests.