具有錐形曲道的分合被動式微混合器

(Split and recombine micromixer with tapered curved microchannels)

具有Dean渦流、分合流道和衝擊流效應。設計微混合器的幾何特徵，利用商用CFD軟體模擬的方式，找出不同圖樣特徵的微結構對混合效率的影響。同時以微機電製程製作出實際尺寸的微混合器，在光學顯微鏡下觀測墨水溶液的混合效應，可快速獲得某一高度橫截面中流場與濃度場的定性結果，並運用影像處理方法，可獲得流道縱截面的混合指標。

We demonstrate a novel parallel laminar micromixer with two-dimensional staggered curved channels with tapered structures. Dean vortex flows are produced in curved rectangular channels by centrifugal forces. The tapered channels' split structures result in the mainstream's uneven split and the diffusion distance reduction between the two fluids. Furthermore, when one stream is injected into the other, the impingement effects increase the mixing strength. Cross-sectional concentration distributions and particle trajectories are utilized to numerically examine the flow characteristics inside the curved microchannel. To evaluate the mixing performance of the designed micromixer, four different designs of a curved channel micromixer are introduced for comparison. The mixing index of the staggered curved-channel mixer with a tapered channel is 20% higher than those of the other curved-channel mixers, i.e. the staggered curved-channel mixer with sudden contracted channels, the staggered curved-channel mixer with uniform channel width and the continuous curved-channel mixer. However, a comparison of the pressure drop penalty for the mixing is also reported. The pressure drop of the staggered curved-channel mixer with a tapered channel is about 50% higher than the other two. The effects of various Reynolds numbers (Re) and channel configurations on mixing performances are investigated regarding the experimental mixing indices and the computational interfacial patterns. The Dean vortex and split and recombine (SAR) effects appear to improve mixing when the Re is increased above 5. At the Re of 50, the channel length necessary for mixing is 5 times shorter compared to the case where the Re equals 1. The comparison between the experimental data and numerical results shows a very similar trend.