A New Model of Polymers in Flow

Recent experimental evidence has shown that polymer chains compress in flow at semi-dilute concentrations. It has been assumed in all models of polymer flow behaviour that the chains extend in flow. A new model of polymers in flow in semi-dilute solution is presented where the chains compress. The chains are modeled as simple Hookean dumbbells exposed to compressive hydrodynamic forces. Equating the hydrodynamic and elastic forces predicts chain compression with shear rate. The model predicts both the power law behaviour observed for polymer shear thinning and the measured decrease in radius with shear rate with reasonable accuracy.