Page 108 - ebook fluid mechanics_finalize

FLUID MECHANICS

Example 4.16

An orifice meter consists of a 100 mm diameter in a 250 mm diameter pipe (Figure 4.15),

and has a coefficient discharge of 0.65. The pipe conveys oil of specific gravity 0.9. The
pressure difference between the two sides of the orifice plate is measured by a mercury

manometer, that leads to the gauge being filled with oil. If the difference in mercury levels

in the gauge is 760 mm, calculate the flow rate of oil in the pipeline.

Pipe Area, A1

P1 P2

V1
Figure 4.15 : Orifice
V2

X
Solution to Example 4.16
Orifice area A2 C C

Let v1 be the velocity and p1 the pressure immediately upstream of the

orifice, and v2 and p2 are the corresponding values in the orifice. Then, ignoring

losses, by Bernoulli’s theorem,

p 1 + v 1 2 = p 2 + v 2 2 ——————(1)
 2 g  2 g

v 2 2 − v 1 2 = p − p 2 ——————(2)
1
2g 

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