Shearbanding Instability and Patterns in Granular Shear Flows

When a (dense) granular material is sheared in shear-cell experiments, shearing remains confined to a narrow localized zone (``shearband'') near the moving boundary. Such shear-banding has also been realized in the molecular dynamics simulations of granular plane Couette flow for a range of densities (even without gravity) in the rapid flow regime. In this talk I will present the shear-banding instability of granular shear flow via an order parameter equation. \\[4pt] [1] Weakly nonlinear theory of shear-banding instability in granular plane Couette flow: analytical solution, comparison with numerics and bifurcation, Priyanka Shukla and Meheboob Alam, Journal of Fluid Mechanics 2010, {\bf 665}, p. 1-50. \\[0pt] [2] Landau-type order parameter equation for shear banding in granular Couette flow, Priyanka Shukla and Meheboob Alam, Physical Review Letters, {\bf 103}, 068001, 2009. \\[0pt] [3] Universality of shear-banding instability and crystallization in sheared granular fluid, Meheboob Alam, Priyanka Shukla and Stefan Luding, Journal of Fluid Mechanics, {\bf 615}, p. 293-321, 2008.