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- Thread starter david90
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Then find the area of a 1.5 inch circle, double it and see if it the same as the area of a three inch circle.

In practise you would have to consider the differences n friction between the two systems, but I don't think that's what you're asking.

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russ_watters

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Two 1.5 inch diameter tubes do not have the same total diameter as one 3 inch diameter tube. This is an easy calculation. Do it and you will find out which is the larger, slower channel, and which is the smaller, faster one.

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russ_watters

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Bernouli's equation is P=1/2 rho*V^2

p=dynamic or velocity pressure

rho=density of air

V=velocity of air

This is a classic problem where the static pressure in a vessel is completely converted to velocity pressure in the opening. So to find velocity, enter pressure and density and solve for velocity. Area/radius is nowhere to be found.

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But Bernoulli's says nothing about the pressure/force causing the fluid to move in the first place.

The relevant effect in a situation where you are considering a change in velocity due to a change in channel diameter is the Venturi effect. Venuri observed, in part,that constricting a flow of fluid caused it to speed up.

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Originally posted by russ_watters

1psi on a 1 square foot opening area is 144 pounds of force. 144x the force, but you are moving 144x the air, so it cancels out.

but it's not converted at the end, the pressure to velocity, it happens at the very beginning

use a vacum for example, say it has on setting, when you turn it on it begins sucking, now if you attach one of those tubes to get the edges, the air moves in quicker and you can feel that there's more suction because the same amount of air has to go through a smaller space

here's a better example if you have a ballon and you fill it with air, then poke a needle the air that will go trough that hole created will move faster than if you take scissors and cut a big one on the top

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