Abstract
The effect of fluid properties and operating conditions on the generation of gas–liquid Taylor flow in microchannels has been investigated experimentally and numerically. Visualisation experiments and 2D numerical simulations have been performed to study bubble and slug lengths, liquid film hold-up and bubble velocities. The results show that the bubble and slug lengths increase as a function of the gas and liquid flow rate ratios. The bubble and slug lengths follow the model developed by Garstecki et al. (Lab chip 6:437–446, 2006) and van Steijn et al. (Chem Eng Sci 62:7505–7514, 2007), however, the model coefficients appear to be dependent on the liquid properties and flow conditions in some cases. The ratio of the bubble velocity to superficial two-phase velocity is close to unity, which confirms a thin liquid film under the assumption of a stagnant liquid film. Numerical simulations confirm the hypothesis of a stagnant liquid film and provide information on the thickness of the liquid film.
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Abbreviations
- A :
-
Cross-section area (m2)
- C :
-
Color function (VOF) (−)
- d :
-
Diameter (m)
- f :
-
Break-up frequency (s−1)
- \(\mathbf{F_\sigma}\) :
-
Capillary force (Pa/m)
- k :
-
Constant (−)
- \(l_{1,\infty}\) :
-
norms in the spurious currents evaluation (m/s)
- L :
-
Length (m)
- m :
-
Constant (−)
- \(\mathbf{n}\) :
-
Normal to the interface (−)
- P :
-
Pressure (Pa)
- Q :
-
Flow rate (m3/s)
- r :
-
Radius (m)
- U :
-
Velocity (m/s)
- W :
-
Dimensionless velocity (−)
- w :
-
Width (m)
- x, y :
-
Axis in 2D simulations (−)
- α:
-
Volume fraction (−)
- β1,2 :
-
Constant (−)
- δ:
-
Liquid film thickness (m)
- δ I :
-
Dirac distribution (interface) (−)
- \(\varepsilon\) :
-
Fraction of area (−)
- λ1,2 :
-
Constant (−)
- μ:
-
Dynamic viscosity (Pa . s)
- ρ:
-
Density (kg/m3)
- σ:
-
Surface tension (N/m)
- \(\varvec{\Upsigma}\) :
-
Viscous stress tensor (Pa)
- B:
-
Bubble
- ch:
-
Channel
- G:
-
Gas phase (air)
- h:
-
Hydraulic
- in:
-
Gas inlet
- L:
-
Liquid phase
- S:
-
Slug
- SC:
-
Spurious currents
- TP:
-
Two-phase
- Bo TP :
-
Bond number \( Bo \;=\; {\frac{(\rho_{\rm{L}} - \rho_{\rm{G}}) d_{\rm h}^2 g}{\sigma}} \)
- Ca TP :
-
Capillary number \( Ca \;=\; {\frac{\mu_{\rm L} U_{\rm TP}} {\sigma}} \)
- Re TP :
-
Reynolds number \( Re \;=\; {\frac{\rho_{\rm L} U_{\rm TP} d_{\rm h}}{\mu_{\rm L}}} \)
- We TP :
-
Weber number \( We \;=\; {\frac{\rho_{\rm L} U_{\rm TP}^2 d_{\rm h}}{\sigma}} \)
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Acknowledgments
This work was financed by the French “Agence Nationale de la Recherche” in the framework of the project MIGALI no. ANR-09-BLAN-0381-01. We also acknowledge the support for this project from the CNRS research federation FERMaT, such as the CALMIP project for providing computational resources.
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Abadie, T., Aubin, J., Legendre, D. et al. Hydrodynamics of gas–liquid Taylor flow in rectangular microchannels. Microfluid Nanofluid 12, 355–369 (2012). https://doi.org/10.1007/s10404-011-0880-8
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DOI: https://doi.org/10.1007/s10404-011-0880-8