Monday, June 16, 2008 - 2:40 PM
Room 9 (McKimmon Conference Center)
97

The Impact of Fluid Elasticity on Wetting

Yuli Wei1, S. Garoff1, E. Rame2, and Lynn M. Walker1. (1) Carnegie Mellon University, Pittsburgh, PA, (2) National Center for Space Exploration Research, Cleveland, OH

The impact of fluid elasticity on the dynamic wetting of polymer solutions is important because many fluids, even those that are normally considered Newtonian, exhibit non-Newtonian behaviors in the high shear environment of the wedge-like geometry near a moving contact line. Even though this behavior is on the microscopic scale, it has significant impact on wetting on the millimeter scale. Our experimental work shows that shear thinning reduces the curvature of the free surface near a moving contact line as compared to a Newtonian fluid having the same zero-shear viscosity. The origins of the reduced curvature have been successfully elucidated in lubrication models using a constitutive relation with power law shear thinning. However, we have also observed that elasticity increases the curvature of the free surface. The origins of the enhanced curvature due to elasticity are not clear yet. In this talk, we focus on the impact of fluid elasticity on dynamic wetting. Both experimental and theoretical results will be discussed. The fluids we use are the dilute solutions of high molecular weight polyisobutylene (PIB) which exhibit elasticity dominated rheology with minimal shear thinning. Their wetting behaviors are compared to both a Newtonian fluid having the same viscosity and their oligomer “solvent”. We will discuss an analysis of the hydrodynamics resulting in the observed enhanced curvature.