**9.1 Channel creation and some other characteristics**

Channel creation is derived from two different phenomena: First is the energy transformation that occurs in the wall because the system continually transforms translational energy into rotational energy. Secondly a vortex whatever its sign is creates a channel of opposite sign. In oder to understand the latter suppose a positive vortex near a wall. The vortex make the particles that lie between it and the wall start spinning or *rotate*, due to viscosity, in the opposite direction causing a vorticity input - in this case negative - to the system.

There are three important features on the channels. The first and most important is that the channels transport vorticity from the walls inside the cavity and also diffuses vorticity along the route to nearby channels in proportion to the existing vorticity gradient. Secondly a positive channel always wraps a negative vortex and a negative channel always wraps a positive vortex. And finally channel thickness is function of the Re number.
