Why pressure is lower at the small bore of a venturi

[thomas49th]

Hi, why is it that in a venturi system the pressure is lower when the diameter of the cross sectional area is smaller?

I do not understand why pressure can be considered a form of "energy". I can understand that energy must be conserved and due to the reduction in the diameter the increase in speed (K.E increase) means a reduction in this pressure energy

Can someone please help me get my head around why this is the case?

Thanks
Thomas

 

[stewartcs]

Hi, why is it that in a venturi system the pressure is lower when the diameter of the cross sectional area is smaller?

I do not understand why pressure can be considered a form of "energy". I can understand that energy must be conserved and due to the reduction in the diameter the increase in speed (K.E increase) means a reduction in this pressure energy

Can someone please help me get my head around why this is the case?

Thanks
Thomas

It's considered energy because it requires work for the fluid to flow...i.e. pressure times volume equals work. You could also rewrite it as pressure time area = force, and force times distance = work. Since area times length (distance) is volume, pressure times volume equals work. Which means it requires energy in the form of pressure acting on a volume of fluid to get it to flow.

So if you look at the Bernoulli equation the first term would be the "pressure head" and is representative of this energy.

CS