SURFACE GRAVITY-WAVE EXPERIMENTS ON SHEAR-THINNING FLUIDS

The phase velocity of surface gravity waves in a horizontal canal has been measured for six viscous shear thinning fluids. The viscosity of these shear thinning fluids was less than 0.07 Pa s for shear rates of the order 100 s-1. At a shear rate of 0.1 s-1, which was more represe ntative for the wave motions in this study, viscosities were observed at several Pa s for some of the fluids. Even though the fluids had lar ge viscosities the experimental results fit better to the phase veloci ty calculations for an inviscid fluid than to standard models based on temporal wave decay. The wave velocity was even slightly larger than predicted by inviscid theory at larger wave numbers.