| Summary: | 碩士 === 國立中興大學 === 機械工程學系 === 92 === This study presents the numerical simulations and experiments of fluid mixing in a microchannel with different aspect ratios. The convection-diffusion equation for species concentration is analyzed using the spectral method for a three-dimensional microchannel. The simulation results include the velocity profile, mixing intensity and the concentration distribution of the microchannel. Effects of the mixing process are primarily controlled by the parameters including the average velocity of the flow, diffusion coefficient, the aspect ratio and the location of mixing region. For the experiments, the micromachining technique was used to fabricate the microchannel of different aspect ratios with silicon wafer. The channels have the same width b=500μm but different depths h=100.3, 56.7, and 26.6μm. Glass was bonded on the wafer surface for flow visualization. The mixing efficiency is estimated by using pH dye in the indicator stream, as the two colorless fluids changed to red color during the mixing process. Based on the theoretical model, the diffusion coefficient of the working fluids has been evaluated. In addition, both the average mixing intensity and the diffusion length can be used as an index of mixing phenomenon.
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