What causes positive vorticity?

Question

(hint, it's a trick question) first right answer gets the stars!

Answer 1

Vorticity is just a fancy word for spin. Positive vorticity is taken to be a counterclockwise rotation., and it can be caused by:

a) Shear - this is the turning effect you see if you hold a pencil between your fingers (as if praying) and push just your right hand forwards... the pencil will turn counterclockwise.

b) Curvature - place a barrier (.e.g a small rock) in a stream and you force the water to flow around the sides and then twist back behind the rock. You will often see a little spinning eddy, which may then drift downstream.

If you choose your rock shape correctly - and the stream is flowing at the right speed - you may see the water behind the rock bank up on the left-hand side (looking down from above), with less water on the right-hand side. The constant attempts of the stream to equalise the water amounts can cause the gurgling sound that many people find pleasant.

Answer 2

Everything that Enough said was fairly well stated with the exception that vorticity is a microscopic measure of rotation in a fluid. It is expressed mathematically as the curl of the velocity ( vorticity = Del X V ), which is in terms of partial derivatives. It does have both a shear and a curvature component.

Answer 3

Positive vorticity advection, "occurs where a wind vector flows through the lines of vorticity from higher values toward lower values of vorticity (in other words higher value of vorticity are advecting downstream the reverse is true for negative vorticity advection).

Sorry, no trick answer for you