Spout States in the Selective Withdrawal of Immiscible Fluids through a Nozzle Suspended above a Two-Fluid Interface

摘要

In selective withdrawal, fluid is withdrawn through a nozzle suspended above the flat interface separating two immiscible, density-separated fluids of viscosities v_(upper) and v_(lower) = λv_(upper)- At low withdrawal rates, the interface gently deforms into a hump. At a transition withdrawal rate, a spout of the lower fluid becomes entrained with the flow of the upper one into the nozzle. When λ = 0.005, the spouts at the transition are very thin with features that are over an order of magnitude smaller than any observed in the humps. When λ = 20, there is an intricate pattern of hysteresis and a spout appears which is qualitatively different from those seen at lower λ. No corresponding qualitative difference is seen in the hump shapes.