Wave celerity on a shear-thinning fluid film flowing down an incline

This letter presents a phenomenological model predicting the celerity of long surface waves on a non-Newtonian fluid flowing down an inclined plane. We show that, for a shear-thinning fluid, the celerity is greater than the well-known value c = 2 U 0 . The developed model points at the significant effect of the viscosity disturbance and also provides a likely explanation for the decrease in threshold for the instability.