A fundamental method for measuring viscosity involves a viscometer made from concentric cylinders. See Fig. 1.8. The fluid for which the viscosity is to be measured is placed between the two cylinders. The torque generated on the inside fixed cylinder by the outer rotating cylinder is measured through a torque measuring shaft. The force required to cause the cylinder to spin and the velocity at which it spins are also measured. Then the viscosity may be calculated in the following way:
The shear stress in the fluid is equal to the force, F applied to the outer cylinder divided by the surface area of the internal cylinder, A.
Was this article helpful?