Pressure theory applied to a Venturi tube

[extricate]

Hi,

I'm a little confused about the pressure in the inlet/outlet and the throat of a Venturi tube.

Why is the pressure in the inlet/outlet greater than in the throat? I thought that because air is needed to flow into a smaller space so the pressure has to be greater?

Pardon me. I've self-learning.

Thanks for your time.

 

[tiny-tim]

welcome to pf!

hi extricate! welcome to pf!

it's conservation of energy (density) …

Bernoulli's equation is simply a conservation of energy (density) equation

(and pressure is energy density: pressure = work done per displaced volume = energy per displaced volume)

where the tube is narrower, the speed is faster, so the kinetic energy density is greater

so the pressure must be less

 

[extricate]

Thanks a lot for the reply.