Calculation of Stress and Torque Transmitted

Now,  is the general stress-strain relation. or     In our case, or    (26.21) Equations (26.20) and (26.21) yields (26.22) Now, and, For the case, when the inner cylinder is at rest and the outer cylinder rotates, the torque transmitted by the outer cylinder to the fluid is or      (26.23) where l is the length of the cylinder. The moment T1, with which the fluid acts on the inner cylinder has the same magnitude. If the angular velocity of the external cylinder and the moment acting on the inner cylinder are measured, the coefficient of viscosity can be evaluated by making use of the Eq. (26.23).