Unmixing Fluids

A very neat video at New Scientist (h/t nc links).  The explanation:

John DeMoss and Kevin Cahill of the University of New Mexico developed the apparatus shown in this video, which is made up of a hollow cylinder with a rotating tube inside it. In this experiment, the space between the cylinders is filled with corn syrup. Drops of food dye are then added and the inner cylinder is rotated slowly, mixing the layers in an orderly fashion.
But the real fun happens when the cylinder's rotation is reversed. This effectively returns the fluid to its initial state, along with the three drops of different coloured dye.
So how is this possible? When corn syrup - a viscous fluid - is mixed, friction dominates inertia and it maintains distinct layers when it flows. This behaviour can be predicted by its low Reynold's number, a measure of how density, speed, and viscosity relate to each other. The phenomenon - called laminar flow - is exploited in many applications like ventilation systems and hydroelectric plants. Click here for a more familiar form of laminar flow.

Check it out.