Unusual pressure profiles and fluctuations during shear flows of liquid crystal polymers

Abstract The spatial dependence of a stress tensor component has been measured for a liquid crystalline solution during cone-and-plate shear flows. The measured stress profile can be used to calculate thermodynamic pressure as a function of position within the flowing liquid crystal. At most shear rates, the pressure profile is highly unusual, with thermodynamic pressure below atmospheric pressure within the rheometer. However, the shape of the time-averaged pressure profile is consistent with the velocity field expected in the rheometer, even at shear rates for which the total thrust on the cone exhibits large time-dependent fluctuations. The measured stress profile can also be used to calculate the second normal stress difference ( N 2 ). The magnitude of N 2 is often surprisingly large, with an unusual oscillatory dependence on shear rate.