Please explain Couette flow.

Maybe you should try looking at a Fluids Mechanic textbook such as Frank White's Fluid Mechanics. These books have lots of pretty pictures that will be more helpful than words.

Thanks

Couette flow is a viscous flow driven by one parallel plate moving relative to another. It is useful in CFD terms as it represents an exact analytical solution of the N-S equations. There is a very good description of the problem and it's solution in J.D.Anderson's 'Computational Fluid Dynamics' (McGraw-Hill)

In theory, Couette flow (Couette 1890) is the flow between (infinite) parallel plates, when the plates are in motion relatively to each other. This is the plane Couette flow.

The circular Couette flow is the flow between rotating concentric (infinitely long) cylinders (when the cylinders have different angular speeds).

In practice the plates or cylinders are finite and there are boundary effects, but the problem is defined far from the boundaries (i.e. far from the extremities of the plates or cylinders).

The problems of interest are when the flow is viscous and when one looks at different speeds (different Reynolds numbers). One of the most practical problem is the Couette flow between rotating cylinders. It has many applications for the theory of rotating flows and transition to turbulence. It has also been very well studied in Laboratory since Couette (1890), Taylor (1923) and more recently by Coles (1965).

For a review of the experiments, have a look at Coles, D., 1965, Journal of Fluid Mechanics, vol. 21, page 385.

If you have more questions, do not hesitate to post them here.

Cheers,

Patrick