Civil - Mechanics Of Fluids - Flow Through Pipes
FLOW THROUGH PIPES
1. What
is meant by energy loss in a pipe?
When
the fluid flows through a pipe, it loses some energy or head due to frictional resistance and other reasons. It is called
energy loss. The losses are classified as; Majorlosses and Minor losses
2. Explain
the major losses in a pipe.
The
major energy losses in a pipe is mainly due to the frictional resistance caused
by the
shear force between the fluid particles and boundary walls of the pipe and also
due to viscosity of the
fluid.
3. Explain
minor losses in a pipe.
The loss
of energy or
head due to
change of velocity
of the flowing
fluid in magnitude or direction is called minor losses. It
includes: sudden expansion of the pipe, sudden
contraction of the pipe, bend in a pipe, pipe fittings and obstruction in the
pipe, etc.
4. State
Darcy-Weisbach equation OR What is the expression for head loss due to
friction?
h_{f} = 4flv^{2} / 2gd
where, h _{f} = Head loss
due to friction (m), L = Length of the pipe (m),
d =
Diameter of the pipe (m), V = Velocity of flow (m/sec)
f =
Coefficient of friction where V varies from 1.5 to 2.0.
5. What are
the factors influencing the frictional loss in pipe flow? Frictional resistance
for the turbulent flow is,
n
i. Proportional to v
ii. Proportional to the density of fluid. iiiProportional to
the area of surface in contact. iv. Independent of pressure.
v. Depend on
the nature of the surface in contact.
6. What is
compound pipe or pipes in series?
When the pipes of different length and different diameters are
connected end to end, then the pipes are called as compound pipes or pipes in
series.
7. What
is mean by parallel pipe and write the governing equations.
When the pipe divides into two or more branches and again join
together downstream to form a single pipe then it is called as pipes in
parallel. The governing equations are:
Q_{1} = Q_{2}
+ Q_{3} h_{f1} = h_{f2}
8. Define
equivalent pipe and write the equation to obtain equivalent pipe diameter.
The single pipe replacing the compound pipe with same diameter
without change in discharge and head loss is known as equivalent pipe.
9. What
is meant by Moody's chart and what are the uses of
Moody's chart?
The basic chart plotted against Darcy-Weisbach friction factor
against Reynold's Number (Re) for the variety of
relative roughness and flow regimes. The relative roughness is the ratio of the
mean height of roughness of the pipe and its diameter (?/D).
Moody's
diagram is accurate
to about 15%
for design calculations
and used for a
large
number of applications. It can be used for non-circular conduits and also for
open channels.
10.
Define the terms a) Hydraulic gradient line [HGL] b) Total Energy line [TEL]
Hydraulic gradient line: It is defined as the line which gives
the sum of pressure head and datum head of a flowing fluid in a pipe with
respect the reference line.
HGL = Sum of Pressure Head
and Datum head
Total energy line: Total energy line is defined as the line
which gives the sum of pressure head, datum head and kinetic head of a flowing
fluid in a pipe with respect to some reference line.
TEL = Sum of Pressure
Head, Datum head and Velocity head
11. What do you understand by the terms a) major energy losses
, b) minor energy losses Major energy losses : -
This loss due to friction and it is calculated by Darcy weis
bach formula and chezy's formula .
Minor energy losses :-
This is due to
i.
Sudden expansion in pipe .
ii.
Sudden contraction in pipe .
iii.
Bend in pipe .
iv.
Due to obstruction in pipe .
12 . Give an expression for loss of head due to
sudden enlargement of the pipe :- he =
(V1-V2)^{2} /2g
Where he = Loss of head due to
sudden enlargement of pipe .
V1 = Velocity of flow at
section 1-1
V2 = Velocity of flow at
section 2-2
13. Give an expression for loss of head due to
sudden contraction : -
hc =0.5 V^{2}/2g
Where hc = Loss of head due to
sudden contraction .
V = Velocity at outlet of
pipe.
14. Give an expression for loss of head at the entrance of the
pipe : - hi =0.5V^{2}/2g
where hi = Loss of head at entrance of pipe .
15.
What are the basic educations to solve the
problems in flow through branched pipes?
i. Continuity
equation .
ii. Bernoulli's formula
.
iii. Darcy
weisbach equation .
16.
Mention the general characteristics of laminar
flow.
�
There is a shear stress between fluid layers
�
'No slip'
at
the boundary
�
The flow is rotational
There is a continuous dissipation of energy due to viscous
shear