CFD study on the interplay between mixing angles and swirl-inducing inlets of a static micromixer: From vortex to engulfment flow

Abstract

Driven by the goal of lowering the critical Reynolds number for the transition from vortex to engulfment flow in passive micro mixers, this research employs 3-D computational fluid dynamics to analyze the impact of geometric features. Specifically, we examine mixing angles and vortex generator placements within a micro T-mixer framework (100 ×100 μm² inlet, 200 ×100 μm² outlet and 3000-μm mixing length). By systematically varying the mixing angle from 0° to 120° at Reynolds numbers of 50, 100 and 150 (within the vortex flow regime), we determine that the 105° angle is the optimal condition for facilitating the transition to engulfment flow. Furthermore, a comprehensive analysis of 24 vortex generator placements at the inlets reveals that a symmetric placement near the mixer corners, with enlarged horizontal offsets, successfully induces engulfment flow at a Reynolds number of 150. Finally, the combined effect of the optimized mixing angle and vortex generator placement results in a substantial increase in engulfment flow and performance index.