Will a Venturi tube with the entry open to a moving fluid act the same as one that has a closed entry with a known pressure/velocity? If I have a windsock in a 10 mph breeze, is the velocity inside the entry point (big diameter) 10 mph? Will the wind velocity at the small end (the exit) be the same, less, or greater than at the big end? Let's put some numbers to it: *Entry wind = 10 mph *Entry diameter = 20 inches *Exit diameter = 10 inches *Windsock length = 50 inches Where I'm going with this is that I have a couple of ideas which need a good stream of air (faster than a typical breeze) and I'd like to use a funnel setup rather than a fan to create it. If it's possible, how can I calculate the output given the input wind speed and the windsock dimensions? (Would a non-flexible tube give better results?) Thanks!