| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系碩博士班 === 97 === In this thesis, the fluids mixing process of different fluid properties in a microchannel is studied numerically. The effects of Reynolds number, geometric structure, fluid properties and location of sidewall injection in mixing efficiency are investigated. At first, compare the different of discretization methods, with the results that the numerical diffusion had a great influence on it. Therefore, we must choose a high-order discretization scheme to solve the velocity and concentration profile. Then, we set baffles in the microchannel and observe the change of flow field and mixing characteristic. Inserting baffles can extend the staying period of fluids, and expand molecular diffusion as well. Furthermore, it can induce recirculation which stirring the fluids to rise the mixing intensity in high Reynolds number. Afterwards, we replace the sidewall injection fluid with a solution of glycerol in water. By varying the glycerol content of the glycerol/water solution, the variation in mixing behavior with changes in the difference in the properties of two fluids (e.g., viscosity, dnesity and diffusivity) was investigated. As the glycerol content increase, Reynolds number wolud decrease as well as the range of recirculation. Molecular diffusion is the main factor in low Reynolds number. For this reason, the increased mixing efficiency would follow the increase of diffusivity. At last, we change the location of sidewall injection next to the recirculation area and we found that is helpful for the fluid mixing in high Reynolds number.
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