Instability of elastic filaments in shear flow yields first-normal-stress differences - art. no. 198301

Using slender-body hydrodynamics, we study the flow-induced deformation of a high-aspect-ratio elastic filament. For a filament of zero rest curvature rotating in a viscous linear shear flow, our model predicts a bifurcation to shape instabilities due to compression by the flow, in agreement with ex perimental observations. Further, nonlinear simulations of this shape insta bility show that in dilute solutions, flexibility of the fibers causes both increased shear thinning as well as significant nonzero first-normal-stres s differences. These stress differences are positive for small-to-moderate deformations, but negative for large-amplitude flexing of the fibers.