Page 183 - Standard Handbook Of Petroleum & Natural Gas Engineering

168 General Engineering and Science

AVp = W( h, - hi)

h, = L - X,
(where L is the relaxed height of the spring) which can be solved for X, the maximum
compression of the spring.
1
2
-kX: + W(L- X, -hi) = 0

2w 2w
X:-Xx, +-(L- h,) = 0
k k

- 0.02+[0.02* - 4[0.02(2-20)]]0'5
-
2
X, = 0.61 ft

The negative root is ignored because it represents an extension of the spring rather
than a compression.
For further information, refer to References 1-5.

FLUID MECHANICS
In fluid mechanics the principles of conservation of mass, conservation of
momentum, the first and second laws of thermodynamics, and empirically developed
correlations are used to predict the behavior of gases and liquids at rest or in motion.
The field is generally divided into fluid statics and fluid dynamics and further
subdivided on the basis of compressibility. Liquids can usually be considered as
incompressible, while gases are usually assumed to be compressible.
Fluid Statics
Pressure is the force per unit area exerted by or on a fluid. In a static fluid the
pressure increases with depth, but according to Pascal's principle it is the same in all
directions at any given depth. Pressure may be specified as either absolute, or gauge,
the relationship between the two being:

where Pp is gauge pressure, Pa is absolute pressure, and Patm is the atmospheric pressure.
Fluid mechanics calculations are generally done in absolute pressure, and hereafter
P will represent absolute pressure.