The University of Jordan
Faculty of Engineering and Technology
Department of Civil Engineering
_________________________________________
Hydraulics Laboratory
0931363
By: Qusai Waleed Al-Qudah · · · · · · · · · · · · · · 1
 Objectives and Liabilities:
1- To calculate the energy line.
2- To determine the relationship between the depth of flow and specific energy.
 Apparatus:
the apparatus consist of a Perspex channel having an adjustable bed .A sluice gate may be
inserted at the upstream end of the working section while , at the downstream end ,an
adjustable tailgate is provided .A reservoir is mounted below the working section .From
this water is drawn by a centrifugal pump for delivery through a flow meter and inlet
valve to the inlet chamber which incorporate an over flow to return excess flow to the
reservoir end a stilling device to provide satisfactory flow conditions in the working
section .The cover of the working section incorporates three picot ( or total head ) tubes
and three seismometer ( or static pressure tapping ) . The flow rate can be measured by a
meter installed in the delivery pipe.
 Concepts and principle:
 Specific energy: Specific energy (E) is the energy head relative to the channel bottom.
If the channel is not too steep (slope less than 10%), and the streamlines are nearly
straight and parallel (so that the hydrostatic assumption holds), the specific energy E
becomes the sum of the depth and velocity head. The kinetic energy correction
coefficient is taken to have a value of one for turbulent flow in prismatic channels but
may be significantly different from one in natural channels.
 Critical depth: the depth at which the specific energy of a given flow rate is at a
minimum.
By: Qusai Waleed Al-Qudah · · · · · · · · · · · · · · 2
 Produce of the experiment:
12345-
Adjust the channel to horizontal position and start the pump.
Allow the flow to run throw the channel for few minute to ensure stability.
Insert sluice gate and initially adjust its opening ygate to 20mm.
Adjust the inlet valve so that y1 =220mm (this will result a constant discharge).
Measure the average Q by taking several readings and measure the flow
corresponding y1 and y2 and E2.
6- Repeat step 5 as you gradually raise sluice gate as instructed by the lab instructor.
7- Adjust the flow as instructed by the lab instructor.
 Theoretical:
 Flow in a channel is nodeled in terms of parameter called the specific energy head of
the flow, E for any cross section shape, the specific energy head at a particular section
is determined as the energy head referred to the channel bed as datum, the specific
energy head is the sum of the depth of flow and velocity head, assuming that the slope
of the channel, and head loss is zero, the specific energy head is defined as:
Where:
E: specific energy head of flow in m.
y: depth of flow in m.
V: velocity of flow in .
g: gravitational acceleration in (
)
.
 Applying the continuity equation:
Where:
A: the wetted cross sectional area for a rectangular channel.
By: Qusai Waleed Al-Qudah · · · · · · · · · · · · · · 3
Then the total specific energy can be expressed:
Where:
Q: volume flow rate in
.
b: channel width in m.
 A relation for a critical depth in a wide rectangular can be found by differentiating ( E
with respect to y ) for which E is minimum:
And where E is minimum, y=yc
After solving:
(
)
and
Where:
q: flow rate per meter width and equal
Emin: minimum specific energy head at critical flow.
By: Qusai Waleed Al-Qudah · · · · · · · · · · · · · · 4
 The calculation about this experiment:
(
)
(
)
Es
(m)
d1
(m)
d2
(m)
260
275
276
264
243
226
186
158
138
119
105
273
278
283
270
243
233
188
158
137
110
97
18
15
10
19
20
25
26
29
30
34
40
By: Qusai Waleed Al-Qudah · · · · · · · · · · · · · · 5
By the graph Emin = 0.048m and yc = 0.049m
 A plot the specific energy head versus the flow depth called the specific energy
diagram, for a constant disgorge Q, there are two different y value for a given specific
energy head E.
 These are known as alternate depths, the two alternative depth represent s two totally
different flow regimes; slow and deep on the upper limp of the curve and fast and
shallow on the lower limp of the curve.
 In the figure it can be seen that at point the flow at a point the specific energy is
minimum and only a single depth occurs, at this point the flow is critical.
 The flow for which the depth is less than critical is supercritical flow, and the flow for
which the depth is greater than critical is subcritical, supercritical velocity is greater
than critical velocity, and sub critical velocity is less than critical velocity.
By: Qusai Waleed Al-Qudah · · · · · · · · · · · · · · 6
 Conclusion:
1- For any depth more than critical depth the velocity will decrease.
2- For any depth min than critical depth the velocity will increase.
 From it the relationship between critical depth and velocity is inverse.
3- When increase or decrease in depth of flow the energy line will increase.
4- The two depths associated with the same energy values are referred to as – Alternate
depths.
5- As discharge increases, the specific energy curves move to the upper right portion of
the chart.
By: Qusai Waleed Al-Qudah · · · · · · · · · · · · · · 7