MIXING ENHANCEMENT IN A CHAOTIC MICROMIXER USING PULSATING FLOW
PROCEEDINGS OF THE ASME FLUIDS ENGINEERING DIVISION SUMMER MEETING 2014
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This study determines the simultaneous effects of spatial disturbance and flow pulsation on micromixing by using three different metrics: concentration distribution, Lyapunov exponent and axial vorticity. Numerical simulations are performed for both steady and pulsating flows through a microchannel made up of C-curved repeating units. Moreover, a straight microchannel is analyzed to compare the effects of chaotic advection and molecular diffusion, the main mechanisms of transverse mixing in the chaotic and straight mixer respectively. Simulations are carried out in the steady flow for the Reynolds number range 1 <= Re <= 50 and in the pulsating flow for velocity amplitude ratios 1 <=beta <= 2.5, and the ratio of the peak oscillatory velocity component to the mean flow velocity, Strouhal numbers 0.1 <= St <= 0.5. It was found that chaotic advection improves mixing without significant increase in pressure drop. The analysis of concentration distribution implied that full mixing occurs after Reynolds number 50 in the steady flow. When the flow is pulsatile, small and moderate values of the Strouhal number (0.1 <= St <= 0.3) and high values of velocity amplitude ratio (beta >= 2) are favorable conditions for mixing enhancement. Moreover, mixing has an oscillating trend along the microchannel due to the coexistence of regular and chaotic zones in the fluid. These results correlate closely with those obtained using two other metrics, analysis of the Lyapunov exponent and axial vorticity.