| Summary: | 碩士 === 國立成功大學 === 機械工程學系碩博士班 === 101 === In this work, we propose and investigate a micromixer which allows three streams of liquids - a core stream sandwiched by two cladding streams - to flow into the main channel with rectangular winglet pairs (RWP) from two inlets. The locations of fluid stream interfaces have significant effect on fluid mixing in a channel with RWP and the increase of fluid interfaces in the proposed mixer is expect to enhance fluid mixing. To take advantage of the proposed design, we have to arrange the RWP appropriately. We examine fluid mixing in the proposed micromixers by numerical simulation and experiment. We use the commercial codes, CFDRC, to simulate the fluid mixing in the micromixer. Comparing the simulation results and fluorescent images shows that the simulation results are reliable. The SU-8 is used to fabricate the mold of micromixers by photolithography. Then, we replicate the mold by PDMS (polydimethysiloxane) and bond the PDMS with a cover glass to complete the fabrication of a micromixer. Finally, we apply the laser confocal spectral microscopy to observe mixing flow in the micromixer. The results show the following trends. (i) When the gap between rectangular winglets of a RWP located slightly asymmetric in the main channel and the centers of the gaps are arranged on both sides of the center of the main channel alternatively, better mixing is achieved. (ii) The RWPs with an angle of attack not greater than 22.5 degrees to the main flow direction may generate longitudinal vortices effectively and lead the distortion of interfaces between fluids to enhance fluid mixing. When the Reynolds number is high, increasing the clearance between the RWPs allows the fully development of the longitudinal vortices downstream which is beneficial to mixing. (iii) When the distance between the RWPs and the channel sidewall is small, more fluids flow through the gap above the top of rectangular winglets for the cases with high Reynolds number and the diffusion length is shorten for the cases with low Reynolds number. These effects enhance fluid mixing. In summary, using the three-stream inlet does enhance fluid mixing and following the above guidelines to arrange five modules of RWPs, the micromixer may achieve a high degree of mixing (〉0.9).
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