Effects of Pulsatility on the Laminar Mixing Surface in Converging Microchannel Flows

Abstract

With the growing interest and development of microfluidic systems, the need for micro-scale laminar flow mixing techniques is evident. Traditional mixing methods often rely upon turbulent flow for mixing which is generally not present on the micro-scale and so alternative approaches must be sought. In this work, we report on the impact of flow pulsatility on the laminar mixing surface/interface formed between two converging microchannel flows. The motivation behind the study is to assess the potential for pulsatility as a possible MEMS-mixing strategy. A 3-D computational model of the converging flow at a 90° junction is developed using the Fluent6® CFD software and the volume-of-fluid algorithm is used to track time-dependent behavior of the interface downstream of the junction. Results thus far have shown that for certain parametric regimes a complex, evolving interfacial distortion can form which propagates and persists downstream of the junction. Time-series for the total interfacial area and the interfacial motion have been extracted from numerical data and spectral analyses have been performed; some interesting nonlinear behavior has been observed. Of particular importance, the results also show that the complexity of the interfacial structure is only significant at higher frequencies (order of kHz) which is appropriate for MEMS-based pumping devices.