You are on page 1of 4

Expt. No.

Date:
STUDY OF UNIFORM FLOW FORMULAE

Aim: To determine the Chezys constant (C) and the Mannings constant (n) for the given
channel bed for the uniform flow.
Theory: An open channel flow is said to be uniform if the flow characteristics like velocity,
depth, slope and c/s remains constant for a given length of channel. Consider section 1-1 and 2-2
as shown in the figure, the forces acting on the water between the sections considered are:
1. The component of the wt. of water in the direction of the flow (ALsin
2. The frictional resistance against the flow of water (fPLV2)
3. Pressure forces at the section 1-1.
4. Pressure forces at the section 2-2.
Where L=length of channel;
A=Area of flow of water;
S=slope of bed;
V=mean velocity of flow;
f=frictional resistance;
P=wetted perimeter.
As the depth of the water at the section 1-1 & 2-2 are the same the pressure forces on these two
sections are same and acting in the opposite direction. Hence they cancel each other. In case of
the uniform flow, the velocity does not change along the length of the channel, thus there is no
acceleration acting on water. Hence the sum of the component of all the external forces in the
direction of the flow must be equal to zero. In short, for this uniform flow to exist the driving
forces (due to gravity) should be equal to the resisting force (due to the friction forces).
ALsin - fPLV2 = 0
V2 =( Asin )/ fP
V=

fP
Asin)/

V=C RS
Where R=A/P =hydraulic depth or hydraulic radius.
C= /f = chezys constant and for small values of ; tan = sin = 0

Therefore, chezys constant = C = V/ RS

And Mannings constant = n = (R2/3 S1/2) / V
Experimental set up : It consists of glass walled (Perspex sheet made) rectangular tilting bed
flume 5m long , 10.3 cm wide and 60 cm deep into which water is supplied by a pump. A sluice
is fitted in the upstream side of the flume. A pointer gauge is used to measure the depth of water
in the channel.
Procedure:
1. A channel bed of tilting is adjusted to certain slope by adjusting the jack.
2. Two or more different section may be chosen. Pointer gauge readings for the bed level
these sections are taken.
3. Water is supplied to the flume by starting the pump. Discharge is adjusted to get the
suitable value of the depth of flow in the flume.
4. After waiting for some time the flow becomes uniform. Then the pointer gauge readings
for the top surface of the water is taken.
5. The water is collected in the discharge tank and rate of flow of water is measured.
6. Steps 2 to 5 are repeated for other values of discharge.

Observations:
i.
ii.
iii.

Area of collection tank = a =

Width of the channel = B =
Initial bed reading of the flume:
a. At section 1-1 = h1 =
b. At section 2-2 = h2 =

Sr.
No.

Slope
S

Section 1-1
H1 (cm)

Section 2-2
H2 (cm)

Height of water
collected in
tank h (cm)

Time to collect the

water in the tank
t (sec)

Observation table :Table 2

Slope

Depth of flow

Y1=
H1-h1
(cm)

Y2=
H2-h2
(cm)

Y=
Y 1 +Y 2
2
(cm)

Formulae:
1.

Y=

Y 1 +Y 2
2

2. A= B Y
3. P= B+2Y
4. R= A/P

5. Qexpt. =

6. V =

a h
t

Q expt .
A

A=
BY
(m2)

P=
B+2Y
(m)

R=
A/P
(m)

Qexpt.
V=
3
Q/A
(m /sec)
(m/sec)

Chezys

Mannings

7. C = V/ RS
8. n = (R2/3 S1/2) / V
The text passage describes an experiment to determine the Chezy's constant (C) and Manning's constant (n) for a given channel bed in uniform flow. It includes the theoretical background, experimental setup, procedure, and formulas used for the calculations.
no_question

the passage does not contain any explicit mathematical questions or word problems that require solving. it provides a detailed description of an experiment and the formulas used, but does not ask the reader to solve any specific problems or calculations.
Given a text passage, determine:
    1. If it contains a mathematical question (including word problems or calculations)
    2. If an answer to that mathematical question is provided in the text

First, describe the content structure you found in 1-2 sentences.

Then provide your analysis in the following format:
TYPE: <one of the following values>
- NO_QUESTION
- SINGLE_QUESTION
- SINGLE_QUESTION_WITH_ANSWER
- MULTIPLE_QUESTIONS
- MULTIPLE_QUESTIONS_WITH_ANSWERS
system
You are on page 1of 4

Expt. No.

Date:
STUDY OF UNIFORM FLOW FORMULAE

Aim: To determine the Chezys constant (C) and the Mannings constant (n) for the given
channel bed for the uniform flow.
Theory: An open channel flow is said to be uniform if the flow characteristics like velocity,
depth, slope and c/s remains constant for a given length of channel. Consider section 1-1 and 2-2
as shown in the figure, the forces acting on the water between the sections considered are:
1. The component of the wt. of water in the direction of the flow (ALsin
2. The frictional resistance against the flow of water (fPLV2)
3. Pressure forces at the section 1-1.
4. Pressure forces at the section 2-2.
Where L=length of channel;
A=Area of flow of water;
S=slope of bed;
V=mean velocity of flow;
f=frictional resistance;
P=wetted perimeter.
As the depth of the water at the section 1-1 & 2-2 are the same the pressure forces on these two
sections are same and acting in the opposite direction. Hence they cancel each other. In case of
the uniform flow, the velocity does not change along the length of the channel, thus there is no
acceleration acting on water. Hence the sum of the component of all the external forces in the
direction of the flow must be equal to zero. In short, for this uniform flow to exist the driving
forces (due to gravity) should be equal to the resisting force (due to the friction forces).
ALsin - fPLV2 = 0
V2 =( Asin )/ fP
V=

fP
Asin)/

V=C RS
Where R=A/P =hydraulic depth or hydraulic radius.
C= /f = chezys constant and for small values of ; tan = sin = 0

Therefore, chezys constant = C = V/ RS

And Mannings constant = n = (R2/3 S1/2) / V
Experimental set up : It consists of glass walled (Perspex sheet made) rectangular tilting bed
flume 5m long , 10.3 cm wide and 60 cm deep into which water is supplied by a pump. A sluice
is fitted in the upstream side of the flume. A pointer gauge is used to measure the depth of water
in the channel.
Procedure:
1. A channel bed of tilting is adjusted to certain slope by adjusting the jack.
2. Two or more different section may be chosen. Pointer gauge readings for the bed level
these sections are taken.
3. Water is supplied to the flume by starting the pump. Discharge is adjusted to get the
suitable value of the depth of flow in the flume.
4. After waiting for some time the flow becomes uniform. Then the pointer gauge readings
for the top surface of the water is taken.
5. The water is collected in the discharge tank and rate of flow of water is measured.
6. Steps 2 to 5 are repeated for other values of discharge.

Observations:
i.
ii.
iii.

Area of collection tank = a =

Width of the channel = B =
Initial bed reading of the flume:
a. At section 1-1 = h1 =
b. At section 2-2 = h2 =

Sr.
No.

Slope
S

Section 1-1
H1 (cm)

Section 2-2
H2 (cm)

Height of water
collected in
tank h (cm)

Time to collect the

water in the tank
t (sec)

Observation table :Table 2

Slope

Depth of flow

Y1=
H1-h1
(cm)

Y2=
H2-h2
(cm)

Y=
Y 1 +Y 2
2
(cm)

Formulae:
1.

Y=

Y 1 +Y 2
2

2. A= B Y
3. P= B+2Y
4. R= A/P

5. Qexpt. =

6. V =

a h
t

Q expt .
A

A=
BY
(m2)

P=
B+2Y
(m)

R=
A/P
(m)

Qexpt.
V=
3
Q/A
(m /sec)
(m/sec)

Chezys

Mannings

7. C = V/ RS
8. n = (R2/3 S1/2) / V
user
The text passage describes an experiment to determine the Chezy's constant (C) and Manning's constant (n) for a given channel bed in uniform flow. It includes the theoretical background, experimental setup, procedure, and formulas used for the calculations.

TYPE: NO_QUESTION

The passage does not contain any explicit mathematical questions or word problems that require solving. It provides a detailed description of an experiment and the formulas used, but does not ask the reader to solve any specific problems or calculations.