On the planar extensional viscosity of mobile liquids

Microfluidic rheometry

“…Contraction flows have been used for many years to investigate the extensional properties of complex liquids in macroscale flow geometries (Cogswell, 1972;Williams and Williams, 1985;Binding, 1988;James et al, 1990) by relating the measured pressure drop across a contraction to the imposed flow rate.…”

On the interpretation of data from Converging Flow Rheometers

“…The analysis of Williams and Williams [6] assumes pure planar extensional flow in the sample and locally pure shear flow in the thin lubricant layers. In the absence of inertial, gravitational and surface tension effects, their result implies that the measured stresses should be essentially independent of z and that the tensile stress ap is then given by ap = P-Pe ,…”

“…A detailed description of the Converging Flow Rheometer and its operation was given in [6]. The schematic diagram in Fig.…”

“…The first two, due to Williams and Williams [6] and Secor et al [5] rely essentially on the suppositions that the sample velocity field is determined a priori and is free of shear. This is in contrast to the third method, an adaption of a contraction analysis developed by Binding [10] in which shear is permitted and account is taken of its contribution.…”

“…Williams and Williams [6] described an apparatus with which steady lubricated planar orthogonal stagnation flows of mobile systems were developed. An analysis was presented, relating pressure measurements at various points of the die with the planar extensional viscosity and this was used to interpret the data obtained for Newtonian (Maltose syrup) and Boger [15] fluids.…”