Correlation of capillary entrance pressure drops with normal stress data

The pressure loss at the entrance of a capillary tube was studied as a means of characterizing viscoelastic fluids. Measurements of four polymer solutions were made and correlated with an equation of the form where D is the shear rate and where Hch and λch are a characteristic stress and a characteristic time, respectively, determined independently from viscosity and normal stress measurements. Various theoretical analyses of capillary entrance flow are also compared.