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標題: 科氏力於Y型微流道中影響流體偏向之數值模擬
Simulation of Coriolis-Induced Flow Switching in Inverse Y-junction Microfluidics
作者: 蔡玟駿
Tsai, Wen-Chun
關鍵字: Coriolis force;科氏力;microfluidics;離心力;微流體
出版社: 機械工程學系所
引用: Lee, L. J., Madou, M. J., Lu, Y., Lai, S., Koh, C. G., and Wenner, B. R., “A Novel Design on a CD Disc for 2-Point Calibration Measurement,” Sensors and Actuators, Vol. 91, No. 3, 2001, pp. 301-306. Duffy, D. C., Gills, H. L., Lin, J., Sheppard, N. F., and Kellogg, G. J., “Microfabricated Centrifugal Microfluidic Systems: Characterization and Multiple Enzymatic Assays,” Anal. Chem., Vol. 71, No. 20, 1999, pp. 4669-4678. Ducrée, J., Brenner, T., Glatzel, T., and Zengerle, R., “A Flow Switch Based on Coriolis Force,” Proceedings of 7th International Conference on Miniaturized Chemical and Biochemlcal Analysis Systems, Squaw Valley, California, USA, October 5-9, 2003. Ducrée, J., “Microfluidic Mixing by Actuation of Magnetic Beads on Rotation Lab-on-a-Disk Platforms,” Proceedings of 9th International Conference on New Actuators, June, 14-16, 2004, Bremen, Germany. Ducrée, J., Brenner, T., Glatzel, T., and Zengerle, R., “Ultrafast Micromixing by Coriolis-Induced Multi-Lamination of Centrifugal Flow,” Proceedings of 9th Internation conference on New Actuators, San Diego, Bremen, Germany, October 14-16, 2004, Ducrée, J., Brenner, T., Haeberle, S., Glatzel, T., and Zengerle, R., “Multilamination of Flows in Planar Networks of Rotating Microchannels,” Microfluidics and Nanofluidics, Vol. 2, 2005, pp.78-84. Brenner, T., Glatzel, T., Zengerle, R., and Ducrée, J., “Frequency-Dependent Transversal Flow Control in Centrifugal Microfluidics,” Lab on a chip, Vol. 5, 2005, pp. 146-150. Lee, Y.-K., Deval, J., Tabeling, P., and Ho, C.-M., “Chaotic Mixing in Electrokinetically and Pressure Driven Micro Flows,” Proceedings of the 14th IEEE Micro Electro Mechanical Systems (MEMS), Interlaken, Switzerland, 2001, pp. 483-486. Madou, M. J., and Kellogg, G. J., “LabCD: A Centrifuge-Based Microfluidic Platform for Doagnostocs,” Proceeding of SPIE-Systems and Technologies for Clinical Diagnostics and Drug Discovery, Vol. 3259, 1998, pp. 80-93 Kim, D. S., and Kwon, T. H., “Modeling, Analysis and Design of Centrifugal Force-Driven Transient Filling Flow into a Circular Microchannel,” Microfluidics and Nanofluidics, Vol. 2, No. 2, 2006, pp. 125-140. Thorsen T., Roberts R. W., Arnoki F. H., and Quake S. R., “Dynamic Pattern Formation in a Vesicle-Generating Microfluidic Device,” Physical Review Letters, Vol. 86, No. 18, 2001, pp. 4163-4166. Munson B. R., Young S. F., and Okiishi T. H., “Fundamentals of Fluid Mechanics,” John Wiley & Sons, Inc., Second edtion, 1994. Currie I. G., “Fundamental Mechanics of Fluids,” McGraw Hill, Inc.,Second edtion, 1993. Geschke O. Klank H., and Tellemann P., “Microsystem Engineering of Lab-on-a-Chip Devices,” Wiley-Vch, 2004. Das D., and Arakeri J. H., “Unsteady laminar duct flow with given volume flow rate variation,” ASME J. APP1 Mech., Vol.67, 2000, pp. 247-281, Chen, Chun I, Chen C.-K. and Yang Y.-T., “Unsteady unidirectional flow of second grade fluid between the parallel plates with different given volume flow rate conditions,” Applied Mathematics and Computation, Vol. 137, 2003, pp. 437-500, 張家維,旋轉碟片上胃型微混合器之模擬分析,碩士論文,國立中興大學,2007。 嚴開杰,科氏力誘導之旋轉微流體控制:螢光偵測與可視化實驗,碩士論文,國立中興大學,2007。 吳永奇,微流道內流體的自由液面形狀及流體流動之動態數值模擬,碩士論文,國立清華大學,2004。
本研究模擬旋轉時產生的離心力驅動流體,觀察科氏力對於流體的影響。模擬利用FLUENT軟體採用暫態解方式於VOF數值模型上模擬實驗晶片,流道結構設計為倒Y形狀,倒Y夾角分別為30°至60˚之間,而流道深度為100 μm,寬度則在100至300 μm的範圍。藉由模擬結果主要觀察科氏力對倒Y分叉流道兩出口流量的影響。本模擬發現,流體的流量隨著轉速提高往其中一分叉流道增加,而在某轉速以上流體完全由其中一邊的流道流出,而模擬結果與可視化實驗結果一致。旋轉方向為逆時針轉,流道寬100 μm倒Y夾角30˚、40˚、50˚及60˚的臨界轉速分別為1600、1900、2500及3600 rpm,而固定倒Y夾角為30˚,流道寬度為150、200、300 μm的臨界轉速分別為2100、2500及3600 rpm。模擬亦發現在相同轉速下,科氏力影響的程度隨流道幾何變化而有所差異。
本模擬另一重點為探討嚴開杰 (2007) 實驗結果與本研究模擬結果皆顯示,固定倒Y流道夾角,改變流道寬度w,科氏力影響流體偏向的臨界轉速也一樣隨之提高,此結果與Ducrée et al. (2003) 推導關於離心力與科氏力的理論完全相反。因此我們假設當流體進入倒Y型模擬入口時的流速為影響偏流臨界轉速的關鍵因素,並利用模擬驗證之。旋轉方向為逆時針轉,固定倒Y夾角為30˚,流道寬度為100、150、200、300 μm的臨界轉速分別為5700、4700、4000及3500 rpm。此模擬結果趨勢與Ducrée et al. (2003) 推導關於離心力與科氏力的理論趨勢相同:流道寬度w愈寬,科氏力影響越大。也證明了本研究所推測的因素,當流體進入倒Y型模擬入口時的流速為影響偏流臨界轉速的關鍵因素假設成立。

This thesis reports simulations of flow switch in rotating microfluidics through a separator of inverse Y-shape with an acceleration zone. In this study, the flow field based on the rotating reference frame is simulated using the method of unsteady VOF equation in association with the momentum equations. The Y-separators are 100 μm in depth with various divergence angles (30 - 60 deg) and channel widths (100 - 300 μm). The switch of flow on a fast rotating disk is due mainly to the Coriolis force that propels the fluid toward the transverse direction. The Coriolis force may lead to unequal flow rates between the two outlets of Y-separator and eventually the flow is diverted into one of the outlets above a threshold speed. For the channel width of 100 μm, the threshold rotational speed increases from 1600 to 1900, 2500 and 3600 rpm with an increase of the divergence angle from 30 to 40, 50 and 60 deg, respectively. For the divergence angle of 30 deg, the threshold rotational speed increases from 2100 to 2500 and 3600 rpm with an increase of the channel width from 150 to 200 and 300 μm, respectively.
It is found that the threshold speed that switches the flow in a Y-separator depends strongly on the inlet velocity. For the case without an acceleration zone, in which the inlet and outlet pressures of the Y-separator are set at zero, the threshold rotational speed for the Y-separators with a divergence angle of 30 deg shows to decrease from 5700 to 4700, 4000 and 3500 rpm with an increase of the channel width from 100 to 150, 200 and 300 μm. This variation trend with the change of channel dimension is consistent with the simple formula proposed by Ducrée et al. (2005), but opposite to the one with an acceleration zone.
其他識別: U0005-2608200801304600
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