Couette flow

Another simple flow similar to that of fixed parallel plates can be developed by fixing one plate and allowing the other plate to move with a constant velocity as given in Fig. 4 (c). In this case, the governing equations will remain the same, but the boundary conditions for the moving plates will be different i.e. . Then, the values of constants for Eq. (22) may be obtained as,
                                                  (28)
It follows from Eq. (22) that
                                                  (29)
In dimensionless form, the above equation is written as,
                                                  (30)
This type of flow is known as "Couette flow". The simplest type of Couette flow is the one for which the pressure gradient is zero i.e. the fluid motion is caused by the fluid being dragged along the moving boundary. In such case, , so Eq. (30) simplifies to,
                                                  (31)
It means that velocity varies linearly between two plates.