Agriculture Reference
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Conservation of Momentum
This says that a moving body cannot gain or loss momentum unless an external
force acts upon it.
1.3.1.2 Theories of Hydraulics and Fluid Flow
Pascal's Law
Pascal's law can be stated as follows: “The intensity of pressure at any point of a
closed conduit is equal in all directions.”
thevesselliquidbe“
p
”. According to Pascal's law, the intensity of pressure at every
direction of the vessel will be equal and “
p
”. Since water is a noncompressible liquid
(not compressed/reduced in volume due to pressure), it exhibits the unique trait of
transforming pressure to all directions when in a confined space.
Fig. 1.6
Schematic of
pressure distribution in a
closed vessel
p
p
Continuity Equation/Conservation of Mass
If the flow is steady, and the fluid is incompressible, the mass entering a pipe
That is, mass flow entering
=
mass flow leaving
Or,
ρ
Q
e
=
ρ
Q
l
Since the volume flow rate is the product of area and mean velocity, consider that
velocity of flow at entering section
V
1
cross-sectional area at entering section
=
=
A
1
velocity of flow at leaving section
V
2
cross-sectional area at leaving section
=
=
A
2
Then, applying the law of conservation of mass,
ρ
×
V
1
×
A
1
=
ρ
×
V
2
×
A
2
or,
A
1
V
1
=
A
2
V
2
(1.14)
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