Transcript Document 7562688

CE 230-Engineering
Fluid Mechanics
Lecture # 7& 8
Pressure Variation in Static Fluids
& its Applications
Pressure variation in a static
fluid
Pressure difference between two points in
a static fluid is the weight of unit fluid
column between them
dp/dz = -γ
z +ve up
This equation is valid as long as we are
in the same fluid.


Two possibilities
Constant γ
 Variable γ

What is the pressure at a depth of 35
ft in the tank?
What is the pressure at the bottom of the
tank? S(oil)=0.8
Problem 3.16
What is the maximum pressure in the odd
tank?
Manometry

Use of pressure
change with elevation
to determine pressure
at a point

Use of pressure
change with elevation
to determine the
difference in pressure
between two points
Problem 3.30
Find pressure at pipe B.
Problem 3.39
Find pressure at pipe A.
Problem 3.31
If the air is under atm. P. the water position
is 1.
Find P if l=40 cm. Dia ratio=8, density =
800 kg/m3
Determine the weight of the man if the
piston weighs 50 lb and area in contact
with water is 1.5 ft2
3 ft
Problem 3.42
determine the difference in pressure
between points A and B.
What if γ is variable?
(Compressible fluid)

For air say
γ = pg/RT
in troposphere T=T0-α(z-z0)

Integrate basic equation to get
pressure variation
Figure 3.5 (p. 39)
Temperature variation with altitude for the U.S. standard atmosphere in July (2).