pascals law, hydrostatic law, numericals

1. Course Name: FLUID MECHANICS AND HEAT TRANSFER
Fluid statics

2. Fluid statics
 Fluid pressure at a point:
p=dF/dA
if the force F is uniformly distributed over are A , then
pressure at any point
p= F/A
F= p X A
Units: SI unit N/m2 or Pa
1bar = 100 kpa or 105 N/m2

3. Pascal’s Law:
“Pressure or intensity of pressure at a
point in a static fluid is equal in all
directions”.
Px = Py= Pz

5. Pressure Variation in a fluid at rest:
“Rate of increase of pressure in a vertical
direction is equal to weight density of the
fluid at that point”. : Hydrostatic law

7. Integrating on both side
p=pressure above atmospheric pressure
Z= height of the point from free surfaces
Z = pressure head = p/ρg

8. 1. Absolute pressure: with reference to
absolute vacuum pressure.
2. Gauge pressure: Measured with the help of a
pressure measuring instrument , in which
atmospheric pressure is taken as datum.
3. Vacuum pressure: pressure below the
atmospheric pressure.

9. Relationship between pressures:
Absolute pressure = atmospheric pressure + gauge pressure
Vacuum pressure = atmospheric pressure – absolute pressure
Patm = 101.3 Kpa (at sea level at 150 C)
Atmospheric pressure head = 760 mm of Hg or 10.33 m of water