Howard Stone: Surprises in the Fluid Dynamics of Flows in Simple Geometries

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The Department of Applied Mathematics is pleased to host this series of colloquium lectures, funded in part by a generous gift from the Boeing Company. This series will bring to campus prominent applied mathematicians from around the world.

Speaker: Howard Stone, Princeton University

Date: April 13th, 2017, 4pm, reception to follow

Location: (SMI 120)

Title: Surprises in the Fluid Dynamics of Flows in Simple Geometries

Abstract:The flow of particle-laden fluids occurs widely, including bulk flows at low or high Reynolds numbers, which arise in all manners of applications. We give a few examples of our current work in this area. First we consider flow in a T-junction, which is perhaps the most common element in many piping systems. The flows are laminar but have high Reynolds numbers, typically Re=100-1000. It seems obvious that any particles in the fluid that enter the T-junction will leave following the one of the two main outlet flow channels. Nevertheless, we report experiments that document that bubbles and other low density objects can be trapped at the bifurcation. The trapping leads to the steady accumulation of bubbles that can form stable chain-like aggregates in the presence, for example, of surfactants, or give rise to growth due to coalescence. Our three-dimensional numerical simulations rationalize the mechanism behind this surprising phenomenon. Second, we consider low Reynolds number flows in channels and porous systems with dead-end pores. We document how salt gradients, via a mechanism referred to as diffusiophoresis, can remove particles from dead-end pores or deliver particles into such pores. The transport can be size dependent and we explore the phenomenon using experiments and modeling. We suggest how the mechanistic ideas can be used to design processes for cleaning water in energy efficient ways.