In order to make the simulation more realistic, the material needs to be changed from Air to Water. Select Material Assignments then change the Material to Water (Material Samples).
Boundary Conditions / Forces
In this problem, we are asked to move the two cylinders with different speeds in the same direction. This can be done by assigning wall conditions to both faces of the cylinders in contact with the flow volume. First, using the Face selection tool, choose the inside face of the flow volume. Then, select the Add drop down menu next to Fluid Flow Conditions and select Wall. A panel will appear with the cylinder face as the location of the wall. From here, change the Wall velocity from Stationary to Moving and Specification to Rotating. The Angular speed of the inner wall of the flow volume is defined in the problem specification to be 0.00135736 [radian s^-1].
Now that the wall boundary has been created for the inner flow volume face, making the wall boundary for the outer flow volume face will be similar. Select the outer face of the enclosure and select Wall from the Add drop down menu.
Now that both rotating cylinders have been defined, a free slip condition will be put on both ends of the flow volume. This is also done using the Wall tool. Pick Wall from the Add drop down menu. Select the top and bottom faces of the flow volume with the Face selection tool. Add these faces to the Location and then change Flow specification to Free slip. Use the picture below for guidance.