(283f) Shear Induced Demixing in Large Amplitude Oscillatory Shear Flows

Peterson, J. - Presenter, University of California, Santa Barbara
Leal, G., University of California Santa Barbara
Entangled polymer solutions can exhibit enhanced light scattering and demixing for a broad range of flow geometries in both steady and unsteady flows. The resulting compositional inhomogeneity can lead to dramatic changes in the flow field relative to what would be predicted for the same fluid with a uniform composition. A connection between shear induced demixing and shear-banding-like transitions is well established in simple shear flow, but comparatively little theory has been developed to understand flow induced demixing in more general flow types. Describing inhomogeneous flows with a standard two-fluid model, we have found that shear induced demixing in large amplitude oscillatory shear flow has the same general character as shear induced demixing in simple shear flow. Through a combination of asymptotic methods, we are able to predict stability boundaries and shear banded steady states for a well-entangled polymer solution in a large amplitude oscillatory shear flow. These predictions are confirmed through a direct numerical simulation of the full two-fluid model.