| Summary: | 碩士 === 國立成功大學 === 機械工程學系 === 104 === A novel micromixer is proposed and fluid mixing in the mixer is investigated numerically. The first stage of the proposed mixer is similar to the original T-shaped micromixers. Two different fluids entering the two inlets have the first confluence at the beginning of the first main mixing channel. At the end of the first main mixing channel, it is connected to the second stage, where the mixing fluid splits into two streams; each of them takes a 90-degree turn into a sub-channel. While one of the stream flows through two clockwise 90-degree bends, the other stream flows through two counterclockwise 90-degree bends. Then, the two streams recombine at the second T-junction and flow into the second main mixing channel. Inducing flow engulfment at high Reynolds number (Re) in the T-junction is necessary for the enhancement of fluid mixing in the present micromixers. However, an ordinary grid-based simulation is hard to generate accurate solutions for fluid mixing with affordable mesh sizes because of the numerical diffusion at high Re. Therefore, a particle tracking method with the diffusion model and a backward random-walk Monte Carlo simulation are applied to the present cases to circumvent numerical diffusion. The results obtained by the two methods show that they are in good agreement. As expected, at high Re, higher mixing performance occurs due to the engulfment flows in the two T-juctions. Moreover, the effect of split-and-recombine sub-channels and 90-degree bends also contribute to the mixing performance at high Re. From further investigation of the different lengths of the two main mixing channels, it is found that the micromixer at higher Re should go with the longer first main mixing channel to generate better mixing performance. The proposed micromixer generates much greater mixing efficiency than the original T-shaped micromixer with only one straight main mixing channel does.
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