SELF-SUSTAINED OSCILLATORY FLOW AND FLUID MIXING IN GROOVED CHANNELS

We examine numerically and experimentally self-sustained oscillation a nd fluid mixing in grooved channels with different groove lengths. The critical Reynolds number for the onset of self-sustained oscillation decreases as the groove length becomes larger, but oscillatory flow is found to arise from the same Tollmien-Schlichting waves triggered by a sheer layer above the groove. Momentum transfer due to the oscillati ng parts of the flow is analyzed by looking at the oscillatory stress and the production of oscillatory energy. Fluid mixing processes betwe en the channel and groove flows are also explained by a particle advec tion procedure. The agreement between numerical and experimental resul ts is satisfactory.