Onset of Instability of Power-Law Fluid in Couette Flow

Abstract

The critical Reynolds numbers at the onset of instability of a Newtonian and a power-law fluid, respectively, in the annulus between two coaxial cylinders, with the inner cylinder rotating and the outer cylinder stationary, are determined theoretically based on Galerkin’s method. For the Newtonian fluid, Galerkin’s method is equally convergent as methods used previously. Experiements were made using Carbopol as a power-law fluid with a flow behavior index of about 0.5. The measured values of the critical Reynolds number are lower than the predicted values by about 9%.