FLOW BEHAVIOR OF VISCOELASTIC POLYMER SOLUTION IN THE EXPANSION CHANNEL

The upper-convected Maxwell (UCM) model was used to describe the rheological properties of polymers. A finite volume method (FVM) for the numerical solution of viscoelastic flows through an abrupt expansion channel is presented. Although there have been many successful numerical predictions of elastic fluid flows,the Weissenberg number ( We) which stands for the elastic is low. With the FVM, stable solutions are found for high Weissenberg number (the elasticity levels up to We = 3.2), further extending the range of previous similar simulations. The simulations reinforce the point that the FVM can be used as a viable alternative for the solution of viscoelastic problems. Through the results of numerical simulations, the contours of velocity and stream function are drawn and micro-scale sweep efficiency is calculated quantitatively. Numerical results show that the viscoelasticity of polymer solutions is the main factor influencing the sweep efficiency. With increasing elasticity,the flowing area in the dead end is enlarged significantly, thus the area with immobile zones becomes smaller, the microcosmic sweep efficiency increases. The visco-elastic nature of the displacing polymer fluids can in general improve the displacement efficiency in pores compared to using Newtonian fluids. This conclusion should be useful in selecting polymer fluids and designing polymer flooding operations.