Nonlinear simulation and linear stability analysis of viscous fingering instability of viscoelastic liquids

Abstract

In this study, the viscous fingering instability of miscible displacement involving a viscoelastic fluid is investigated using both linear stability analysis and computational fluid dynamics for the first time. The Oldroyd-B model is used as the constitutive equation of a viscoelastic fluid. Here, it is assumed that one of the displacing fluids or the displaced one is viscoelastic. In linear stability analysis, the quasi-steady state approximation and six order shooting method are used to predict the growth rate of the disturbance in the flow. It is shown that the flow is more stabilized when the elasticity (Weissenberg number) of the displaced or displacing viscoelastic fluid is increased. In the nonlinear simulation, using the spectral method based on Hartley transforms and the fourth-order Adams-Bashforth technique, the effect of the viscoelastic fluid on this instability has been studied. Evaluation of concentration contours, mixing length, sweep efficiency, and transversely average concentration show that the elasticity has a significant effect on the fingering instability and the flow becomes more stable by increasing the Weissenberg number.