Residual film thickness following immiscible fluid displacement in noncircular microchannels at large capillary number

In the present work an analytical and numerical study is presented in order to determine the residual fluid film thickness of a power-law fluid on the walls of a rectangular horizontal channel when it is displaced by another immiscible fluid of negligible viscosity. The mathematical model describes the motion of the displaced fluid and the interface between both fluids. In order to obtain the residual film thickness, m , we used a singular perturbation technique: the matching asymptotic method; in the limit of small capillary number, Ca . The main results indicated that the residual film thickness of the non-Newtonian fluid decreases for decreasing values of the power-law index, which is in qualitative agreement with experimental results.

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Immiscible fluid displacement in nonlinear seepage flow

Journal of Applied Mechanics and Technical Physics ◽

10.1007/bf00913186 ◽

1972 ◽

Vol 9 (2) ◽

pp. 205-207

Author(s):

M. G. Bernardinet ◽

V. M. Entov

Keyword(s):

Seepage Flow ◽

Immiscible Fluid ◽

Fluid Displacement

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Single bubble slug expulsion of initially static superheated sodium in a heated pipe and variation of residual film thickness on the channel walls

International Communications in Heat and Mass Transfer ◽

10.1016/0735-1933(77)90033-1 ◽

1977 ◽

Vol 4 (5) ◽

pp. 341-351

Author(s):

M Özgü

Keyword(s):

Film Thickness ◽

Single Bubble ◽

Residual Film

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The Effect of Surface Wettability on Viscous Film Deposition

ASME 2009 7th International Conference on Nanochannels, Microchannels and Minichannels ◽

10.1115/icnmm2009-82263 ◽

2009 ◽

Author(s):

Alexandru Herescu ◽

Jeffrey S. Allen

Keyword(s):

Contact Angle ◽

Film Thickness ◽

Capillary Number ◽

High Speed ◽

Glass Tube ◽

Contact Angles ◽

Film Deposition ◽

Surface Wettability ◽

Working Fluid ◽

Uniqueness Of The Solution

The viscous deposition of a liquid film on the inside of a capillary has been experimentally investigated with a focus on the relationship between the film thickness and surface wettability. With distilled water as a working fluid tests were run in a 622 microns diameter glass tube with contact angles of 30° and 105°, respectively. In the first set of experiments the tube was uncoated while in the second set a fluoropolymer coating was applied to increase the contact angle. A film thickness dependence with the contact angle θ (surface wettability) as well as the Capillary number in the form hR ∼ Ca2/3/cosθ is inferred from scaling arguments. For partial wetting it may explain the existence of a thicker film for nonzero contact angle. It was further found that the non-wetting case of 105° contact angle deviates significantly from the existing theories, the film thickness presenting a weak dependence with the Capillary number. This deviation as well as the apparent non-uniqueness of the solution is thought to be caused by the film instability (rupture) observed during the tests. The thickness of the deposited film as a function of the Capillary number was estimated from the liquid mass exiting the capillary and the gas-liquid interface (meniscus) velocity, and compared to Bretherton’s data and a correlation proposed by Quere. The film thickness measurements as well as the meniscus velocity were determined with the aid of a Photron high speed camera with 10000 frames per second sampling capability coupled with a Nikon TE-2000 inverted microscope and a Precisa electronic balance.

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