On the dynamics of vortex-wall interaction in low viscosity shear thinning fluids

Abstract

We apply a pseudospectral method to numerically study the dynamics of vortices found within a low viscosity non-Newtonian fluid with a Carreau fluid rheology. The application of a Carreau fluid rheology avoids the commonly observed complications in power-law models at zero strain-rate. We find that fluids with a shear thinning rheology will preserve the small scale features of the flow. In particular, for vortex-solid wall interactions, shear thinning fluids can exhibit behavior associated with Newtonian fluids at a much higher Reynolds number. This can include secondary vorticity generation, and multiple vortex-bottom collisions each marked by periods of higher bottom shear rates. Using a variety of experimentally determined parameters from the literature, we argue that these results have direct application to many non-Newtonian fluids, including non-Newtonian fluid mud layers found on lake and ocean bottoms.