Behavior of Dilute Polymer Solutions in the Inlet Region of a Pipe

The behavior of dilute polymer solutions in the inlet region of a round tube has been analyzed with a Rivlin-Ericksen approximation to describe the fluid properties. It is shown that for dilute polymer solutions, shorter inlet length and increased pressure drop in the inlet region are predicted and that those changes are due to fluid elasticity. Available experimental evidence showed some qualitative support for the inlet-length predicted by the theory. Further, the pressure drops in the inlet region of various tubes have been measured for water and dilute solutions of polyethylene oxide; the results show fair agreement with the predictions.