Page 53 - ebook fluid mechanics_finalize

FLUID MECHANICS

c. Inverted Differential U-Tube Manometer

Now consider an inverted differential manometer whose two ends are connected

to two different points A and B. Let us assume that the pressure at point A is more than

that at point B, a greater pressure at A will force the light liquid in the inverted U-tube to

move upwards. This upward movement of liquid in the left limb will cause a
corresponding fall of the light liquid in the right limb as shown in Figure 3.12. Let us take

C-D as the datum line in this case.

Figure 3.12 : Inverted Differential Manometer

We know that pressures in the left limb and right limb below the datum line are equal.

p
Pressure C at C = Pressure p
D

at D

For the left right limb : p = p −  P h
2
D
B
h 
For the left hand limb : p = p −  P 1 − Q h
C
A
since, p = p
D
C
p −  P h −  Q h = p −  P h 2
B
1
A
2
p − p =  P h −  P h −  Q h
B
2
1
2
A

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