Liquid interface oscillation dynamics in a radial Hele–Show cell

Interface dynamics between immiscible liquids with a large difference in viscosities is experimentally studied by varying the frequency and amplitude of oscillations, the relative initial position of the liquids, and the thickness of the working liquid layer. It is shown that with an increase in the amplitude of the interface oscillations, a finger-like instability, which has a local character, manifests itself in a threshold manner on its surface. The found instability of the oscillating boundary is similar to the Suffman–Taylor instability, which develops when a viscous fluid is uniformly displaced from a slot channel (porous medium).