GENERALIZED ANNULAR COUETTE-FLOW OF A POWER-LAW FLUID

The steady laminar axial flow of a power-law non-Newtonian fluid in the annular space between two long coaxial cylinders, with one of them in motion and an imposed pressure gradient, is studied. The pressure gradient may assist or oppose the drag on the fluid due to the moving cylinder. Expressions for the volume rate of flow are derived analytically for two cases, one in which there is a maximum or minimum in the velocity profile within the annular region of interest and another in which there is not. A quantitative criterion is established to distinguish between these two cases. The solutions allow direct calculation of the volumetric flow rate for all values of the annulus aspect ratio, the power-law index, and the dimensionless pressure gradient parameter.