From flow focusing to vortex formation in crossing microchannels
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The paper is concerned with the experimental and numerical investigations of the vortex formation and flow focusing inside a cross-shaped microchannel domain. The local hydrodynamics in the junction area, upstream of the focusing region, is analyzed with the aim to characterize the onset and the evolution of the vortical structures, in correlation with the operating parameters. The numerical simulations based on a finite-volume approach are validated by direct flow visualizations using epifluorescence and confocal microscopy. The main result of the study is a flow pattern map, providing comprehensive information on the flow dynamics inside the microchannel junction as a function of the input flow rates and the corresponding Reynolds numbers. The flow pattern map identifies the limits of the flow focusing regime and the critical values of the parameters at which the vortical structures are formed. Beyond the breakdown of the classical flow focusing scenario with one focused output stream, flow patterns with two and four output streams are identified.
KeywordsMicrochannel Cross-junction Vortex formation Flow focusing Fluorescence microscopy CFD
The authors acknowledge Dr. eng. Catalin Marculescu for his assistance in fabrication of the microchannels and also the financial support received from the grant UEFISCDI, projects PN-II-ID-PCE-2012-4-0245/2013 and PN-II-PT-PCCA-2011-3.1-0052. The work of Iulia Rodica Damian was funded by the Sectoral Operational Programme Human Resources Development 2007–2013 of the Ministry of European Funds through the Financial Agreement POSDRU/159/1.5/S/132397.
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