EXAMPLE: DRAG FLOW (COUETTE FLOW) BETWEEN TWO PARALLEL PLATES Consider two flat parallel plates separated by a distance b as shown in the Figure. The top plate moves in the x-direction at a constant speed V, while the bottom plate remains stationary. The fluid between the plates is assumed incompressible. As the top plate moves the fluid is dragged along. This type of flow is often referred as Couette flow. It has important applications in lubrication applications (such as rotating journal bearings) and instruments for measurement of viscosity. Prove that the velocity profile for this type of flow is linear. What is the volume flow rate? W V b y x Now consider the previous problem, but this time a pressure gradient is also imposed. This type of flow is typically experienced within an extruder. What is the velocity profile, Q and shear stress?