Another way to go. The narrowest point is less Venturiego nozzle pressure. It's like found in the center of the lowlands of atmospheric ( weather ). This causes larger than hurricanes weather.
Except that here we have a much shorter way from the boom to the lowlands....
Huricane flows from areas of high pressure to areas of low pressure.
QUOTE (Greg Locock @ Mar 29 2011, 21:25)
Step back from the equations, and think about what would happen if you put a disc with a hole in it up to the airflow. Now stretch the disc out along the axis of the hole. All the air in the disc bit will be still 'see' disc ahead of them, not the hole you'd like them to go for. A big wodge of stagnated air will build up ahead of the venturi. For the equations just use continuity and Bernouilli, for the lossless case./QUOTE
In this reasoning, the disc does not have thickness. The reasoning for the classic windmill, to which all are used: flat disk, with virtually no thickness. Therefore, the classic windmill has a low efficiency, because this disc is not dispensed air mass and its speed is only such as wind.
The venturi nozzle are two cones and a not insignificant thickness of 25 meters. And now this whole mass of air that is housed in a venturi nozzle is involved in the flow through it. It should be noted that the cones are of unequal length. Cone output is 30 % longer than the input... why? Well, because this is the output cone of doing it at low pressure in the narrowest point.
With reduction in pressure, is involved the whole mass of air in which the output is a cone, that is, the average disk X 16m. Cone can not be shorter because they do not provide laminar flow, which is a prerequisite for good work Venturi nozzle. With disorders of movement ( for a short cone ) in action will take part, only a small mass of air, to lower pressure. The condition is llaminar flow, because the cone has to be quite so long. For that produces a significant vacuum in the narrowest point, causing fresh air to the input cone...
Andrew