A rotating viscometer consists of two 0.6 m long co-axial cylinders with Ø = 0.3 m and 0.32 m respectively. (The gap between the cylinders is 1 cm.) The external cylinder is fixed and the inner cylinder is rotating at 2.5 rpm.
(a) Calculate the shear stress on the cylinder walls.
(b) What is the shear stress in the fluid at 5 mm from the walls?
(c) Calculate the power required to drive the rotating viscometer.
The fluid is a SAE40 oil (density: 871 kg/m3, viscosity: 0.6 Pa.s). Remember, the power equals the product of the angular velocity time the torque between the fluid and the moving cylinder.