Originally Posted by rayxi

If you folded the vanes back up it would be just short cylindrical piece of tubing. With a short length of round ducting I could make one of those in 15 minutes. Then I could rig up a test to measure the pressure drop using your shop vac idea. Might be a fun science project.

Have you thought about using some smoke in combination with the shop vac to see if it creates a vortex? You really need to put the thing in a section of tube for a proper test though. The boundary effects are significant for creating the vortex.