(413e) Rinsing Flows: Exploiting Viscoelastic Liquids

Rinsing flows refer to processes where a jet of one fluid (the jet fluid) is used to ablate a second liquid that coats a planar substrate (the coating liquid).  Using an impinging jet of water to rinse coating fluids of varying rheology has been considered to understand the flow structures of the resulting hydraulic jumps qualitatively and quantitatively. We investigated the interactions of the two-fluid system during the transient growth of the flow profile, observing rheological dependencies on the magnitude, velocity, and topography. Various instabilities were also observed, including Saffman-Taylor fingering and a flow profile dependency on the local viscosity ratio of the rinsing fluid to the coating fluid.

Four classes of test fluids, each having approximately equal viscosities at low shear, have been chosen for this study: a Newtonian solution, a viscoelastic polymer solution, a Boger fluid, and a shear-thinning, inelastic colloid suspension. The presence of shear-thinning of the coating liquid influenced the overall velocity of the radial growth, while determining the geometry of the driving front. The dependence of these results on the local rheology was supported by experiments on Newtonian fluids of various shear viscosities. The presence of elasticity was seen to dampen the disturbances of the hydraulic jump, influence the overall jump height, and vary the radial growth of the jump.  These observations were supported by experiments of Boger fluids with varying elasticity.