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The theory developed by Jiang et al. (1987) for a flowing suspension of neutrally buoyant spheres in an incompressible Newtonian fluid is further tested for a limiting case of the Couette viscometer, for a limiting case of the cone-plate viscometer, and for the parallel-plate viscometer. Compared with the available data for the Couette viscometer, the average errors are less than 2.6% for y <0.10, 4.2% for y < 0.15, and 5.5% for y < 0.20. The predictions of its limiting case for very dilute suspensions are capable of representing these data with errors less than 4% for y < 0.08. KEYWORDS Suspension Apparent viscosity Effective viscosity Couette viscometerCone-plate viscometer Parallel-plate viscometer.

Row through an inclined tube of a suspension of uniform, neutrally buoyant spheres in a second-order fluid has been analyzed using the theory of (Li and Slattery, 1989). The result predicts that the spheres will migrate toward the center of the tube, forming a core with a maximum packing density. The velocity and concentration distributions agree qualitatively with previous observations. The predicted apparent viscosity is significantly lower than that obtained with a cone-plate viscometer (limiting case in which the angle between the cone and the plate approaches zero), or a parallel-plate viscometer, in which uniform concentration distributions are expected.

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