Exploiting the confined twin-jet instability for micro mixing enhancement

A method for exploiting hydrodynamic instability for enhancement of micro-mixing is proposed, studied numerically and demonstrated experimentally. The confined twin-jet geometry is selected as the baseline unstable flow, since it undergoes a Hopf bifurcation at low Reynolds numbers. It is shown that by adding weak fluidic perturbation to the mean flow, significant amplification of unstable modes results, leading to enhanced mixing in laminar flow. Good agreement was found between Computational Fluid Dynamics (CFD) and experimental results for the critical Re, for which instability sets-in, and its related Struohal number. In order to evaluate mixing efficiency, backward tracing particle was performed using the computed flow field. Mixing is estimated based on particle's location in time and space. A parametric mixing study was performed and its results are presented and discussed. It is shown that mixing was significantly enhanced when the perturbation frequency was matched with the baseline's most-unstable Struohal number, even for sub-critical Reynolds number.