Header menu link for other important links
X
Layered two-phase flows in microchannels with arbitrary interface-wall contact angles
Published in Elsevier Ltd
2018
Volume: 192
   
Pages: 1058 - 1070
Abstract
In this work, we study unidirectional, fully developed, layered two-phase flows in microchannels, where the interface meets the wall at an arbitrary contact angle. Interfacial tension causes the interface to take the form of a circular arc, with a radius that depends on the contact angle. The momentum equations must therefore be solved on a domain with boundaries that are, in general, not iso-coordinate surfaces. We adopt the technique developed by Shankar (2005a), which extends the use of eigenfunctions to arbitrary shaped domains, and apply it to layered flows for rectangular and circular cross-sections of the channel. This method is computationally efficient and allows us to analyze in detail the effect of the contact angle on flow properties. We focus on the case of a rectangular channel, which is commonly encountered in microfluidic applications, and consider two distinct cases: (a) free interface whose equilibrium contact angle is a function of fluid wetting properties, and (b) pinned interface whose apparent contact angle is determined by fluid flow rates. We calculate the relationship between the volume fractions (holdups) and flow rate fractions of the fluids and show that a non-zero contact angle can significantly restrict the range of permissible flow rates. This range is greater when the less viscous fluid has a greater affinity for the wall. For fixed flow rates, the residence time of a fluid is found to increase as its affinity for the wall increases. The pressure drop, which directly impacts operational costs, is found to be lower when the more viscous fluid is more wetting. This non-intuitive result is explained in terms of the corresponding variation in fluid volume fractions. © 2018
About the journal
JournalData powered by TypesetChemical Engineering Science
PublisherData powered by TypesetElsevier Ltd
ISSN00092509
Open AccessNo
Concepts (18)
  •  related image
    Contact angle
  •  related image
    Eigenvalues and eigenfunctions
  •  related image
    Flow rate
  •  related image
    Microchannels
  •  related image
    Microfluidics
  •  related image
    Viscosity
  •  related image
    Viscous flow
  •  related image
    Volume fraction
  •  related image
    Wetting
  •  related image
    APPARENT CONTACT ANGLE
  •  related image
    ARBITRARY INTERFACES
  •  related image
    Circular cross-sections
  •  related image
    Computationally efficient
  •  related image
    FLUID VOLUME FRACTION
  •  related image
    MICRO FLUIDIC APPLICATIONS
  •  related image
    Rectangular channel
  •  related image
    ZERO CONTACT ANGLE
  •  related image
    Two phase flow