The very thin tube A of mean radius r and length L is placed within the fixed circular cavity as shown. If the cavity has a small gap of thickness t on each side of the tube, and is filled with a...

The very thin tube A of mean radius r and length L is placed within the fixed circular cavity as shown. If the cavity has a small gap of thickness t on each side of the tube, and is filled with a Newtonian liquid having a viscosity
, determine the torque T required to overcome the fluid resistance and rotate the tube with a constant angular velocity of
. Assume the velocity profile within the liquid is linear.