Extensional flow affecting shear viscosity: Experimental evidence and comparison to models

The effect of extensional flow on apparent shear viscosity has never previously been directly measured nor is it often considered. Here, for the first time, through using a novel configuration (two-phase response under flow), we have viscoelastic polymer solution in controlled and kinematically mixed manner. We show, via control transient experiment, that deformation depends not only rate but also extension their relative direction: thinning being enhanced by parallel reduced perpendicular flow, respectively. A 62% reduction with was seen this work. then test ability commonly used Giesekus Carreau–Yasuda (incorporating generalized rate) models to predict against our data. model found correct qualitative behavior both depending fitting parameters, provided loosely quantitative agreement. Conversely, description does capture behavior, most significant errors occurring (i.e., expansion) flows. This work emphasizes rarely noted shortcomings latter approach when experimental analysis engineering design flows are additionally present.