BEHAVIOR OF POLYMER SOLUTIONS AND MELTS IN SHEARING AND ELONGATIONAL FLOW USING STREAK PHOTOGRAPHY AND BIREFRINGENCE.

摘要

An experimental analysis has been carried out for the kinematics of a Newtonian (glycerin solution) and a non-Newtonian (polyacrylamide solution) fluid undergoing flow past a radially oriented cylinder in both a converging and uniform flow field. The glycerin and polyacrylamide solutions are found to follow Newtonian and power law behavior, respectively, in Poiseuille flow between parallel plates and the lubrication approximation was found to give an accurate description of the kinematics in the converging flow geometry. The local flow kinematics near the cylinder end were, however, found in the two flow geometries to be the same for both fluids and well described by the solution to the Stokes equations for constant free stream flow past a long slender prolate spheroid. Elongation rates in the vicinity of the cylinder axis are significantly enhanced over those in the mainstream and in a region within about two diameters downstream of the cylinder end the kinematics can be classifed as "strong" becoming "weak" thereafter.;Birefringence measurements were made with four polymer melts: poly(1-butene), polyethylene, polypropylene and polystyrene in Poiseuille flow between parallel and converging walls both with and without the cylinder inserted. An interpretation of the isoclinic pattern in the flow between parallel walls is given as well as the birefringence behavior of the polystyrene melt which was found to be anomolous. The lubrication approximation was also found to apply to the polyethylene flow kinematics but not for the polystyrene melt in converging flow. With the cylinder inserted in the converging flow the normal stresses near the end were estimated to be near those measured at the wall.