An Experimental Investigation of Gas-Bubble Breakup in Constricted Square Capillaries

Abstract

ABSTRACT Recent advances in enhanced oil recovery involve generating foam within underground porous media to displace the oil. We investigate experimentally the important snap-off mechanism of gas-bubble generation in constricted square capillaries. Sixteen mm movies record the snap-off of smaller bubbles from a larger bubble as it moves through the constriction. The time required for bubbles to snap off once they move past the constriction, and the length of the generated bubbles are obtained from viewing the movie frames. The bubble capillary number, μUT/σ, is varied from 10−5 to 5 (10−3) by adjusting the wetting fluid viscosity, μ, and the surface tension, σ, by the addition of aqueous surfactants to mixtures of glycerol and water, and by altering the bubble velocity, UT. Results show that a dimensionless time to snap-off depends weakly on the capillary number, and that the generated bubble size increases almost linearly with increasing capillary number. Surfactants create dynamically immobile interfaces for surfactant solutions of 1 wt% sodium dodecyl benzene sulfonate (SDBS) and Chevron Chaser SD1000. Compared to the surfactant-free solutions, the time to breakup with surfactants increases by a factor of about three; generated bubble length increases by at most a factor of three.