Many microfluidic applications involve chemical reactions. Most often, the flow is predominantly laminar, and without active or passive mixing enhancement the reaction time can be extremely long compared to the residence time. In this work we demonstrate the merits of the combination of flow pulsation and geometrical characteristics in enhancing mixing efficiency in microchannels. Mixing was studied by introducing a mixing index based on the gray level observed in a heterogeneous flow of pure water and water colored by rhodamine B. The effects of the injection geometry at the microchannel inlet and the use of pulsed flows with average Reynolds numbers between 0.8 and 2 were studied experimentally and numerically. It appeared that the mixing index increases with the nondimensional residence time (τ), which is inversely proportional to the Reynolds number. In addition, we show that the mixing efficiency depends strongly on the geometry of the intersection between the two fluids. Better mixing was achieved with sharp corners (arrowhead and T intersections) in all cases investigated. In pulsed flow, the mixing efficiency is shown to depend strongly on the ratio (β) between the peak amplitude and the mean flow rate. Optimal conditions for mixing in the microchannels are summarized as a function of Reynolds number Re, the ratio β, and the geometries.
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December 2014
Research-Article
Flow Pulsation and Geometry Effects on Mixing of Two Miscible Fluids in Microchannels
Houssein Ammar,
Houssein Ammar
Laboratoire de Thermocinétique
Lunam, Polytech Nantes
UMR CNRS 6607,
Lunam, Polytech Nantes
UMR CNRS 6607,
Nantes 44306
, France
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Ahmed Ould el Moctar,
Ahmed Ould el Moctar
Laboratoire de Thermocinétique
Lunam, Polytech Nantes
UMR CNRS 6607,
Lunam, Polytech Nantes
UMR CNRS 6607,
Nantes 44306
, France
Search for other works by this author on:
Bertrand Garnier,
Bertrand Garnier
Laboratoire de Thermocinétique
Lunam, Polytech Nantes
UMR CNRS 6607,
Lunam, Polytech Nantes
UMR CNRS 6607,
Nantes 44306
, France
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Hassan Peerhossaini
Hassan Peerhossaini
1
Laboratoire Interdisciplinaire des Energies de Demain (LIED)
Université Paris-Diderot,
Sorbonne Paris Cité UMR CNRS 8236,
email: hassan.peerhossaini@univ-paris-diderot.fr
Université Paris-Diderot,
Sorbonne Paris Cité UMR CNRS 8236,
Paris 75013
, France
email: hassan.peerhossaini@univ-paris-diderot.fr
1Corresponding author.
Search for other works by this author on:
Houssein Ammar
Laboratoire de Thermocinétique
Lunam, Polytech Nantes
UMR CNRS 6607,
Lunam, Polytech Nantes
UMR CNRS 6607,
Nantes 44306
, France
Ahmed Ould el Moctar
Laboratoire de Thermocinétique
Lunam, Polytech Nantes
UMR CNRS 6607,
Lunam, Polytech Nantes
UMR CNRS 6607,
Nantes 44306
, France
Bertrand Garnier
Laboratoire de Thermocinétique
Lunam, Polytech Nantes
UMR CNRS 6607,
Lunam, Polytech Nantes
UMR CNRS 6607,
Nantes 44306
, France
Hassan Peerhossaini
Laboratoire Interdisciplinaire des Energies de Demain (LIED)
Université Paris-Diderot,
Sorbonne Paris Cité UMR CNRS 8236,
email: hassan.peerhossaini@univ-paris-diderot.fr
Université Paris-Diderot,
Sorbonne Paris Cité UMR CNRS 8236,
Paris 75013
, France
email: hassan.peerhossaini@univ-paris-diderot.fr
1Corresponding author.
Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received July 31, 2013; final manuscript received April 6, 2014; published online September 10, 2014. Assoc. Editor: Daniel Maynes.
J. Fluids Eng. Dec 2014, 136(12): 121101 (9 pages)
Published Online: September 10, 2014
Article history
Received:
July 31, 2013
Revision Received:
April 6, 2014
Citation
Ammar, H., Ould el Moctar, A., Garnier, B., and Peerhossaini, H. (September 10, 2014). "Flow Pulsation and Geometry Effects on Mixing of Two Miscible Fluids in Microchannels." ASME. J. Fluids Eng. December 2014; 136(12): 121101. https://doi.org/10.1115/1.4027550
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