1.

Introduction
Water hammer is a pressure surge or wave caused when a fluid (usually a liquid but
sometimes also a gas) in motion is forced to stop or change direction suddenly
(momentum change).
Water hammer is a commonly observed phenomenon taking place during a fluid flow.
The pressure of a liquid in a conduit and its discharge are interdependent. Every change
in discharge induces a corresponding change in pressure and vice versa. The changes of
pressure at water hammer may be insignificant, but could also be large, sometimes
leading to the rupture of a pipe-line, or of other devices forming part of the pipe-line
system. Such breakdowns are by no means rare. Another danger of water hammer is the
difficulty of estimating in advance, whether the water hammer imperils the system in a
specific case, or whether its effects can be neglected. Water hammer may be the cause of
other adverse effects besides an increased mechanical stress of the pipe-line and the
attached equipment. It may affect the regulation of hydraulic systems or distort the results
of measurements of hydraulic quantities.
The surge tank or surge shaft is a structure, which is an essential part of the
conveyance pressure conduit system. Surge tanks are usually associated with high
power development schemes where water is taken to the powerhouse through tunnel.
A surge tank is apparently a sizeable water receptacle interposed between the
powerhouse and the high-pressure penstock on one side and low pressure tunnels and
reservoir on the other side. The main function is to protect the low-pressure conduit
system from high internal pressure.

Whenever there is an abrupt load rejection by the power system, the mass of water in
the conveyance system intern get suddenly decelerated and the process give rise water
hammer phenomenon.

The object of surge tank is to intercept and dampen the high-pressure waves and not
allow them in low pressure system. Due to surge tank the entire pressure condition
the upstream side of surge tanks can be designed as low-pressure system while the
penstock between the surge tanks and the powerhouse will be designed as conduits,

1
which resist high water pressure. We can say that surge tank is a buffer that absorbs
shock pressure arising due to sudden load change in power turbine.

The surge tank also serves a secondary function, which may be called as storage
function like an accumulator. It can absorb the access discharge from the reservoir or
provide extra water in emergency through turbine whenever needed. This storage is
needed when the turbine is switching over from one steady state to another steady
state.
a) Function of the surge chamber
The surge chamber functions in three ways:

I. It reduces the distance between the turbine inlet and the nearest free water
surface, and there by greatly reduces the intensity of the free water waves.
Moreover the water hammer effects in the aqueducts above the surge
chambers are reduced to such degree that they can in many cases be neglected
in practical design, and only the short length of the conduit below the surge
chamber must be designed to withstand them.

II. With a reduction of load the surge chamber acts as releaf opening into which
main conduit flow is partly or wholly diverted. The water level in the chamber
therefore rises until it exceed the level in main reservoir thus retarding the
main conduit flow and absorbing the surplus kinetic energy.

III. Finally, when starting up or when increasing load, the chamber acts as a
reservoir which will provide sufficient water to enable the turbine to pick up
their new load safly and quickely, and to keep them running at the increased
load until the water level in the surge chamber has fallen below its original
level. Sufficient head is thereby created to accelerate the flow of water in the
conduit until it is sufficient to meet the new demand.

2
 Water hammer is a phenomena due to pressure change in closed pipes caused
when flowing water in pipe lines is accelerated or decelerated by closing or
opening a valve or changing the velocity of water rapidly in some other
means.
There are basically two approaches for the water hammer problem. In first
compressibility of water are neglected, the resulting analysis is called rigid
water hammer theory. In other theory elastic effects are taken into account
and are called elastic water hammer theory.
2. Problem Statement
In the design of water conveyance system of hydropower project, special
consideration has to be given to transient flow condition, particularly if the
conveyance system is long such transient conditions are due to governor operation of
the turbine resulting in an altered value of discharge. In case of penstock pipes such
change in the steady state normal discharge triggers off a high-pressure wave, which
sweeps the penstock and may cause damage to the pipe. The designs of the pipe are
channel has to be safe against such transient phenomenon.
Water hammer is the pressure wave which occurs with the sudden change in the
penstock velocity, valve closure or turbine load rejection. It is normally associated
with long penstock where the pressure wave does not return from the end of the
penstock before the valve is fully closed. A pressure wave up to 2100 feet head is
possible in hydro plants, if the valves are closed too rapidly. Negative pressure from
gate or valve open require even more cases, if the pressure in the penstock goes below
the vapor pressure of the water then it will vaporize similar to water boiling or
cavitation. The extreme vacuum will collapse penstock and other conveyance
facilities.

3. Objectives

Followings are the main objectives to be achieved by this study

 Study the design of surge tank used in hydropower plant
 Application of surge model for design of surge tank

3
  Optimal design of surge tank using surge model
 To review the various options available for the selection of surge system

4. Literature Survey

Sudden shutdown of hydro electric plant or change in water flow through hydraulic
turbine may cause problem ranging from rupture of penstock due to water hammer to
runner speed changes that cause the line current of the generator to vary from the
desire frequency. The water hammer theory was mainly developed by L.
Allievi(1925) and independently by N. Joukowsky(1925) around the beginning of the
twentieth century. Since that time analysis of the water hammer phenomena since
then it is undergoing a continuous refinement. Computerized solutions are available
now available for most of the problems.

The following approaches shall be implemented for the analysis of water hammer and
for the investigation of the best-suited geometry and dimensions of the surge tank and
the relevant appurtenances

Pannakian (1995) has shown that the following equation apply for the case when the
pipe is considered to be compressible. The equation of equilibrium for the element of
the water is

(4.1)

And continuity equation is

(4.2)

Where
h = pressure heading pipe
v = velocity of water
g = acceleration due to gravity

4
 x1 = distance along pipeline measured –ve upstream from valve
a = velocity of pressure wave
t = time
and the velocity of the pressure wave in a pipe is given by following formula

(4.3)

Where
a = velocity of the pressure wave
γ = Specific weight of water
g = acceleration due to gravity
k = volume modulus of water = 43.2 x1061b/ft
e = thickness of the pipe
E = young modulus of elasticity, Ib / ft2
Araki and Kuwabara (1975) have written differential equation for elastic theory of
water hammer and introduced a term for considering head loss simplification of the
equation using finite difference method for solving the equation by inserting
appropriate boundary conditions. This is normally done with special computer
programs. Typical of this computer program was WHAMO, a special program that
was prepared for the U.S. Corps of engineer.

Streeter and Wylie (1979) presented similar equation for solving water hammer
transients in simple pipeline with an open reservoir upstream and a valve at a
downstream point. They have used the method of characteristics to develop a basic
computer program printed in FORTRAN language.

Escher Wyss published a treatise by Nemet (1974) on mathematical model of

hydraulic plants in which he presented a theory on water hammer and the structure for
a I digital computer program to solve .for the pressure increase of water hammer. This
publication also gives the format for the computer system data input.

5
Mosonyi and Seth (1975) Restricted orifice surge tank analysis was introduced by
have developed equations to solve the problem that arise when the restricted orifice
surge tank operates and water hammer causes significant pressure head rise in the
penstock upstream of the surge tank Mosonyi and Seth (1975) developed the theory
and tasted it in a laboratory in Germany for a particular cross sectional area of surge
tank (Warnick. C .C .1984).

Thoma and F. Vogt first established stability conditions of the surge system. They
stated that in order to prevent the development of unstable oscillations the cross-
section of the surge tank should exceed a certain critical magnitude. Later
investigations the impracticability of a general criterion and the necessity of
specifying separate conditions for small and for great amplitudes. According to the
Thoma formula suggested in case of small oscillations, the limit cross-sectional area
of the surge tank is

(4.4)
Where,

n = factor of safety
β = The resistance factor of the tunnel
l = the length of the tunnel
f = the tunnel section
Ho = H -β vo2 = the net head (by neglecting the head loss in the penstock)

Damping of great surges should be investigated by one of the more accurate

mathematical methods. Exceptional care should be devoted to the network load. It
should be finally emphasized in complicated and delicate cases the surge tanl<,
respectively, the entire oscillation system should be preferably be investigated by
model tests. Methods suitable for experimentation have been developed by A. Stucky,
B. Gentilini, E. Scimemi.
An approximate mathematical approach for determining any point of the oscillation
curve was elaborated by W. E. Muller in the thirties, viz. by using jacobi's elliptical

6
 functions and taking into account the first four members of the exponential sequence.
In the same time, based on this study, M.Hampl dealt with the calculation of the
accurate value of the oscillation period. In 1968 J. Gieseck presented another genuine
procedure for computing any point of the surge oscillation in a cylindrical tank.

5. Methodology

a) Brief Description:

This study consists of numerical simulation of surge tank used in high head
hydropower project. Hydraulic design of surge tank concerns itself with two main
aspects, its height and cross-sectional area. The height of the surge tank should be
such that both the upsurge and down surge should be contained within the surge
tank height.

Data Collection:

The data required for hydraulic analysis of High Head Hydropower Project by
using the surge model is obtained from HEPO,W APDA office. The maximum up
surge .
I and down surge evaluated during extreme operating, conditions of the turbine i,e
Instantaneous complete closure and instantaneous complete opening of the
turbine's governors are calculated. The required data will be collected from
relevant department/project.

b) Experimentation: NO

c) Experimental Setup: NO

d) Theoretical Studies:

7
 A comprehensive attempt will be made to study maximum related material and
guide lines for water hammer analysis and hydraulic design of Surge Tank.
Different conditions will be studied and finally most and hydraulically suitable
Surge Tank will be finalized.

e) Result Expected:

 Criteria for optimum efficient and cost effective design will be

incorporated in detail design of structures.

 Efficient Surge System offering maximum capacity of absorbing the surge

waves will be proposed inline with the requirements of the project.

6. Utilization of Study / Research Work

The high head hydropower development is very essential for northern areas of
Pakistan. There is great potential for high head hydropower for the local areas. This
research will be very beneficial for the planers and engineers for development of high
head hydropower projects.
Numerical model will help in optimal design of surge tank before physical model
study and actual fabrication at site. The numerical model is economical and less time
consuming as compared to physical model. This study will provide in depth
knowledge to the personnel involved in hydropower development and planning.

7. Research Time Table:

Literature Review 4 weeks

Data Collection 6 Weeks

8
 Data Analysis and computations 6 Weeks

Report Writing 6 Weeks

Final Submission 2 Week

Total Time 24 Weeks

8. Reference

 Allievi L "Theory of water hammer" E HaImes transproceedings, American society

of mechanical engineering, 1975

 Jaeger. C: “Present Trends In Surge Chamber Design”, Proc. Inst. Mech. E., Vol. 108,
1954

 Mosonyi .E and H.B.S. Seth "The surge tank a device for controlling water hammer"
Water power and Dam construction. Vol 27 No 2 & 3 1975

 U. S. Army Crops of Engineers "water hammer and mass oscillation simulation

program" user manual CEG 002 Washington D. C Office of chief Engineers

 U. S. Department of interior "training course for power operating personnel lesson

3 .Governor for hydraulic turbines" Denver Colo. V. S .Department of interior Bureau
of Reclamation 1975.

9
 Warnick. C. C "Hdropower Engineering"

9. Comments of Supervisor

SIGNATURE OF SUPERVISOR SIGNATURE OF STUDENT

Endst. No. CED/ ___________________________ Dated: _____________/2008

The above proposal duly recommended by the Committee for the Post Graduate
Studies in Civil Engineering in the meeting held on_____________ forwarded to
the Director of Research for the approval of Vice Chancellor.

10
 CHAIRMAN
Civil Engineering Department
University of Engineering & Technology, Lahore.

11