Yichen Guo, The University of Texas at Austin

"Bubble velocity and shape in Hele Shaw cell"

Abstract: Interfacial dynamics is an important class of problems in nonequilibrium physics. One of the most famous phenomena studied within interfacial dynamics is viscous fingering, in which finger-like instabilities occur at the interface between two fluids if a more viscous fluid is displaced by a less viscous one. The first group of people who systematically studied this phenomenon, G.I. Taylor and P.G. Saffman, found that by increasing the pumping rate of the less viscous fluid, the finger width always converges to one-half of the experimental channel width. However, they showed in their paper that any finger width should be allowed, which is known as the "selection problem." Another variant of the selection problem, which shares the exact mathematical description, is that a bubble should travel at twice the velocity of the background fluid. Mark Mineev, a theoretical physicist, was able to solve the bubble selection problem in the limit of no surface tension. In this talk, I will present my experimental data aimed at verifying his theory.