Functional Dependence of Torque Coefficient of Coaxial Cylinders on Gap Width and Reynolds Numbers

Dimensional considerations on the torque coefficient of coaxial cylinders, inner one rotating and outer one at rest, result in the expression CM = f(T/Ri, Re) where Re is the Couette Reynolds number, T is the clearance between the cylinders, and Ri is the inner radius. Experimental data published in the literature and additional data obtained by the authors are analyzed to determine the above functional relationship. It is shown that, depending on the Couette Reynolds number and dimensionless gap width, four different regimes exist and that the fractional characteristics of a coaxial cylinder can accordingly be optimized.