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Flow Through Orifices.

Orifice Discharge into Free Air

An orifice is an opening with a closed perimeter through which water flows. Orifices may have any shape, although they are usually round, square, or rectangular.

Discharge through a sharp-edged orifice may be calculated from:

Q = Ca?2gh

Q= discharge, ft3/s (m3/s)

C =coefficient of discharge

a =area of orifice, ft2 (m2)

g =acceleration due to gravity, ft/s2 (m/s2)

h =head on horizontal center line of orifice, ft (m)


The coefficient of discharge C is the product of the coef- ficient of velocity Cv and the coefficient of contraction Cc. The coefficient of velocity is the ratio obtained by dividing the actual velocity at the vena contracta (contraction of the jet discharged) by the theoretical velocity. The theoretical velocity may be calculated by writing Bernoulli’s equation for points 1 and 2.Thus

hydrualics 6

V2= ?2gh

The coefficient of contraction Cc is the ratio of the smallest area of the jet, the vena contracta, to the area of the orifice.

Submerged Orifices

Flow through a submerged orifice may be computed by applying Bernoulli’s equation to points 1 and 2 in figure below
hydrualics 7

Values of C for submerged orifices do not differ greatly from those for nonsubmerged orifices.

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Kanwarjot Singh

Kanwarjot Singh is the founder of Civil Engineering Portal, a leading civil engineering website which has been awarded as the best online publication by CIDC. He did his BE civil from Thapar University, Patiala and has been working on this website with his team of Civil Engineers.

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2 comments on "Flow Through Orifices."


useful information

taylor says:

This would not work in a non-circular orifice situation.

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