The document discusses laminar and turbulent pipe flow. It states that the transition from laminar to turbulent flow depends on the dimensionless Reynolds number. It also discusses head losses due to friction in pipes and defines head loss as the equivalent height that the fluid needs to be raised to overcome frictional losses. Finally, it explains the water hammer phenomenon that can occur in pipes due to sudden changes in flow rate, describing how it generates pressure waves that travel through the pipe and can damage pipe walls.

1. A N Khudaiwala (L.M.E) G.P.PORBANDAR

2. Objectives Have a deeper understanding of laminar and
turbulent flow in pipes and the analysis of fully
developed flow.
 Calculate the major and minor losses associated with
pipe flow in piping networks and determine the
pumping power requirements.
A N Khudaiwala (L.M.E) G.P.PORBANDAR

3. Introduction
Average velocity in a pipe
• Recall: because of the no-slip
condition, the velocity at the
walls of a pipe or duct is zero.
• We are often interested only in
Vavg or Vm which we usually call
just V.
A N Khudaiwala (L.M.E) G.P.PORBANDAR
Friction force of wall on fluid

4. Laminar and Turbulent
Flows
A N Khudaiwala (L.M.E) G.P.PORBANDAR

5.  Critical Reynolds number (Recr):
Re at which the flow becomes turbulent.
 For internal flow in a round pipe,
• Re < 2300 ⇒ laminar
• 2300 ≤ Re ≤ 4000 ⇒ transitional
• Re > 4000 ⇒ turbulent
 Recr depends upon
• Pipe roughness
• Pipe vibrations
• Upstream fluctuations,
disturbances (valves, elbows, etc.
that may disturb the flow)
A N Khudaiwala (L.M.E) G.P.PORBANDAR
Transition from laminar to turbulent flow
depends on a dimensionless
quantity: Reynolds number, Re.
ν
DVavg
=

6. Head Loss
 In the analysis of piping systems, pressure losses are commonly
expressed in terms of the equivalent fluid column height called
head loss hL.
 It also represents the additional height that the fluid needs to be
raised by a pump inorder to overcome the frictional losses in the
pipe
A N Khudaiwala (L.M.E) G.P.PORBANDAR
gd2
fLV
g
P
h
2
avgL
L =
ρ
∆
=

7. A N Khudaiwala (L.M.E) G.P.PORBANDAR

8. A N Khudaiwala (L.M.E) G.P.PORBANDAR

9. Water Hammer Phenomenon in pipelines
A sudden change of flow rate in a large pipeline (due to
valve closure, pump turnoff, etc.) may involve a great mass
of water moving inside the pipe.
The force resulting from changing the speed of the water
mass may cause a pressure rise in the pipe with a magnitude
several times greater than the normal static pressure in the
pipe.
The excessive pressure may fracture the pipe walls or cause
other damage to the pipeline system.
This phenomenon is commonly known as the water hammer
phenomenon A N Khudaiwala (L.M.E) G.P.PORBANDAR

10. Some typical damages
A N Khudaiwala (L.M.E) G.P.PORBANDAR
Pipe damage in
power station Okigawa
Burst pipe in power
sation Big Creek #3, USA
Pump damage in Azambuja
Portugal

11. 2-high raise in pressure (failure)
A N Khudaiwala (L.M.E) G.P.PORBANDAR

12. Water Hammer
Consider a long pipe AB:
 Connected at one end to a reservoir containing water at a height
H from the center of the pipe.
 At the other end of the pipe, a valve to regulate the flow of water
is provided.
A N Khudaiwala (L.M.E) G.P.PORBANDAR

13.  If the valve is suddenly closed, the flowing water
will be obstructed and momentum will be destroyed
and consequently a wave of high pressure will be
created which travels back and forth starting at the
valve, traveling to the reservoir, and returning back
to the valve and so on.
This wave of high pressureThis wave of high pressure::
1. Has a very high speed (called celerity, C ) which
may reach the speed of sound wave and may create
noise called knocking,
2. Has the effect of hammering action on the walls of
the pipe and hence is commonly known as the water
hammer phenomenon.
A N Khudaiwala (L.M.E) G.P.PORBANDAR

14. The kinetic energy of the water moving through the
pipe is converted into potential energy stored in the
water and the walls of the pipe through the elastic
deformation of both.
The water is compressed and the pipe material is
stretched.
The following figure illustrates the formation and
transition of the pressure wave due to the sudden
closure of the valve
A N Khudaiwala (L.M.E) G.P.PORBANDAR

15. 1-Surge Suppressor
A N Khudaiwala (L.M.E) G.P.PORBANDAR