IJCIET Energy Dissipation Blocks

International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),
ISSN 0976 – 6316(Online) Volume 5, Issue 3, March (2014), pp. 32-49 © IAEME
32
EXPERIMENTS TO STUDY THE EFFECT OF DISSIPATION BLOCKS
UPON ENERGY OF FLOW DOWNSTREAM THE COMPOUND WEIRS
Imad H. Obead
Dept. of Civil Eng.,College of Eng., University of Babylon
Riyadh Hamad
Dept. of Civil Eng.,College of Eng., University of Babylon
ABSTRACT
The objective of this study was to investigate the hydraulic characteristics such as energy
dissipation, reduction of hydraulic jump and roller length on unconventional types of blocks using
the experimental works. Values of the relative energy dissipation ratio (E2/E1), relative length of
hydraulic jump (Lj/Y2), and relative roller length (Lr/∆Y) for different blocks in this study were
found in terms of the primary Froude numbers. Results indicated that the compound weir with (60°
,
90°
) lower V-notch with all dissipation blocks have a high efficiency especially at the high
discharges. Also, the hydraulic characteristics values of applied discharges on the surface of the
triangular cut angles with (45°
, 60°
) were better than other configuration of blocks.
Key words: Dissipation, Blocks, Energy, Compound, Weirs
1. INTRODUCTION
The specific energy of the flow always decreases during the flow. So the specific energy at
any discharge ratio of the flow either decreases or increases. The specific energy of the
discharge ratio is depends on the flow depth (Giglou et al,. 2013). In the small low-head hydraulic
structures, the Froude Number of discharge flow is typically not more than 4.5, which means it is a
low Froude Number flow. Bottom-flow energy dissipater is usually adapted to low-head hydraulic
structure, by means of engineering measures, the hydraulic jump is controlled to the stilling basin,
and energy is dissipated by the Surface vortex roll and a strong vortex turbulence of hydraulic jump.
To improve energy dissipation rate, decrease the length and height of stilling basin, the dissipation
blocks are applied on the apron to form a forced hydraulic jump. Usually, when the energy is
dissipated by hydraulic jump, a serious fluctuating pressure was generated on the stilling basin apron,
INTERNATIONAL JOURNAL OF CIVIL ENGINEERING
AND TECHNOLOGY (IJCIET)
ISSN 0976 – 6308 (Print)
ISSN 0976 – 6316(Online)
Volume 5, Issue 3, March (2014), pp. 32-49
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33
and the fluctuating uplift force will sometimes make the apron unstable. The fluctuating pressure of
hydraulic jump with low Froude Number is very complex (Zhou and Yin, 2011).
Abdel-Aal et al.,(2003) studied and developed theoretical models for the hydraulic jump as
an important method for energy dissipation to predict the depth ratios of the radial hydraulic jumps
at negative steps downstream of the control structures when the stilling basins was ended with a sill.
An experimental program was conducted to enable verification of the developed theoretical models.
Good agreement between theoretical and experimental results was obtained. The developed models
were recommended for use in the design of radial stilling basin to compute the depth ratios which
was needed to complete the dimensioning of the stilling basin.
Irzooki et al., (2005) presented a laboratory experiments to study the hydraulic performance
of stilling basin with unusual shapes of baffle blocks. Seven groups of baffle blocks were selected,
three of these groups were cut with angle (15º, 30º, 45º) horizontally, another three groups were cut
with the same above angles, but vertically, and the seventh group was cut with semi-cylindrical
section. They concluded that the cutting baffle blocks were generally better than the standard blocks
in dissipation of a hydraulic energy and reduction of a hydraulic jump length, but a ratio of drag
force applied on cutting baffle blocks was greater than this ratio on the standard blocks for the same
flow conditions and angle of cut. The cutting baffle blocks gives a greater value of the energy
dissipation which was (80.62%) than the standard blocks and greater value of reduction in the
hydraulic jump length which was(37.5%),also these blocks gives maximum increase of the drag
force ratio which was (97%) greater than its value on the standard baffle block.
Omer et al.,(2008) presented study to indicate the drag coefficient, pressure distribution and
flow types on unconventional types of angularly cut baffle blocks and compared the results with
standard baffle blocks by using the Fluent program and the experimental results. They concluded that
values of the drag coefficient for the vertically cut blocks were less than the horizontally cut baffle
blocks in the same flow conditions. Also, maximum values of applied pressures on the surface of the
vertically cut baffle blocks were less than on other models which makes them more better than
others.
Abbas,(2009) investigated an experimentally the hydraulic performance of the compound
hydraulic jump and plunge pool stilling basin operating under high head for Makhool Dam, two
series of tests were carried out; the first series are on the model as it was designed, while the second
series were on a modified model by adding two rows of chute blocks. The results indicated
that for the first model the stilling basin length can be reduced and there was negative pressure at the
beginning of the jump on the sloping apron with high turbulence and unstable water surface.
After adding the chute blocks, the tests of the second model indicated that the stilling basin length
can be reduced and all pressures were positive with reasonably stable water surface as well as lower
turbulence. Therefore, chute blocks were recommended to be added.
Retsinis et al., (2011) introduced the local change of mechanical energy within inclined
channels in sluice gate and weir flows based on experimental measurements. The dimensionless local
mechanical energy changes, in general loss for sluice gate flows and gain for weir flows were
associated to the dimensionless geometrical characteristics and angle of longitudinal slope of
channel.
Kurukji,(2012) presented an experiments to study energy dissipation for stepped spillway in
addition to the elimination of air pockets which take place at steps by using obstructions along the
edge of steps. The results of the experiments showed that the obstructions were very successful in
eliminating air pockets and had a positive effect on energy dissipation along the stepped spillway, the
results also indicated that the use o these obstructions should be started from second step until the
middle step of the spillway.
Maatooq et al.,(2013) analyzed the Diyala weir problems and compares it with the safe
limit and proposes the treatment for these problems. It was concluded that the scour occurs due to
the position of the hydraulic jump and the sequence depth of the jump was higher than the tail

International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976
ISSN 0976 – 6316(Online) Volume 5, Issue 3, March (2014), pp.
water depth. Some treatment procedures
by presenting a suitable stilling basin as well as recommended to use a low weir at end of basin to
produce a back water curve that should be increase
of a hydraulic jump.
2. EXPERIMENTAL APPROACH
Experiments were carried out in the hydraulic laboratory of the civil engineering department,
college of engineering, university of Bab
rectangular open channel with dimensions of approximately 10 m long with an adjustable slope, 0.45
m deep and 0.3 m wide (as shown in figure 1).
enable visual observation of 10mm thick, and a stainless steel floor. Two movable carriages with
point gauges with accuracy of (0.5mm) were mounted on brass rails at the top of channel sides to
measure the heads over weir and downstream the hydraulic jump
tank by a centrifugal pump with a maximum capacity 40
storage tank to the flume then returns to ground tank by vertical outlet at the end of the flume. Water
discharge was measured by using flow meter. Flume bed was maintained at a horizontal slope during
all of the testing.
Figure (1)
Six sets of experiments were performed for a total of
runs was performed using a triangular cut blocks of (
jump in stilling basin with baffle blocks and end
groups of dissipation blocks (5 runs for each)
hydraulic flume operation mode and stage discharge relation
conditions were selected, and the Parameters of experiment conditions showed in table
(2) show the main details of the compound
6316(Online) Volume 5, Issue 3, March (2014), pp. 32-49 © IAEME
water depth. Some treatment procedures were suggested, these treatments cover this problem
basin as well as recommended to use a low weir at end of basin to
ould be increased the stage of tail water and ensuring the stability
EXPERIMENTAL APPROACH
college of engineering, university of Babylon. This experimental work was performed in a horizontal
m deep and 0.3 m wide (as shown in figure 1). The channel consisted of toughened glass walls
of 10mm thick, and a stainless steel floor. Two movable carriages with
measure the heads over weir and downstream the hydraulic jump. Water was supplied from a sump
tank by a centrifugal pump with a maximum capacity 40 l/sec., raising water by pump from the
ing flow meter. Flume bed was maintained at a horizontal slope during
Figure (1): Hydraulic flume used in present work
sets of experiments were performed for a total of 240 runs. The first set consisting of
triangular cut blocks of (θ=45°
) to simulate a classical hydraulic
baffle blocks and end sills. Further runs consisting of (25 runs) for the rest
dissipation blocks (5 runs for each) for a particular type of compound weir. According
hydraulic flume operation mode and stage discharge relation for compound weirs
selected, and the Parameters of experiment conditions showed in table
compound weir models.
suggested, these treatments cover this problem
basin as well as recommended to use a low weir at end of basin to
the stage of tail water and ensuring the stability
This experimental work was performed in a horizontal
The channel consisted of toughened glass walls to
of 10mm thick, and a stainless steel floor. Two movable carriages with
Water was supplied from a sump
, raising water by pump from the
ing flow meter. Flume bed was maintained at a horizontal slope during
runs. The first set consisting of 30
to simulate a classical hydraulic
runs consisting of (25 runs) for the rest
weir. According to
weirs, the model test
selected, and the Parameters of experiment conditions showed in table (1).Figures

Table (1): Important characteristics of
Compound Weir Model
Model
No.
Rectangular + Half Circle
Notch
Rectangular + Triangular
Notch
Rectangular + Trapezoidal
Notch
Stepped Notch
The main dimensions and specifica
table (2).Figure (3) shows the top view for basins used in this study.
Figure (2): Definition sketch showing dimensions and specifications of compound weir models (all
Important characteristics of compound weir models used in this study
Model
No.
Dimensions (cm)
Height Width Pw
1 25 20 15
2 25 10 15
3 25 20 15
4 25 11.65 15
5 25 5.0 15
5 25 5.0 15
7 25 10 15
8 25 5 15
The main dimensions and specifications of the energy dissipation blocks were presented in
the top view for basins used in this study.
Definition sketch showing dimensions and specifications of compound weir models (all
dimensions are in cm)
weir models used in this study
Weir Angle
R=10 cm
R=5 cm
θ=90°
θ=60°
θ=90°
θ=60°
2-Steps
3-Steps
tions of the energy dissipation blocks were presented in
Definition sketch showing dimensions and specifications of compound weir models (all

Table (2): Dimensions and specifications of the energy dissipation blocks used in the study
Type of
Cutting Angle
Block
Numbers Width (cm)
Triangular
8
8
Horizontal
8
8
Vertical
8
8
In order to evaluate the efficiency of the stilling basin with new types of dissipation blocks,
the experiments were conducted and the necessary measurements for each type
collected. Followed by analyzing the results and then compare it with other
the models most suitable for applicable combination
dissipation ratio and hydraulic jump lengt
(A): Triangular cut
(B): Horizontal cutting angle for dissipation blocks (60
Dimensions and specifications of the energy dissipation blocks used in the study
Dimensions
Width (cm) Length (cm) Height (cm)
5.0 8.0 3.0
5.0 8.0 3.0
5.0 8.0 3.0
5.0 8.0 3.0
5.0 8.0 3.0
5.0 8.0 3.0
evaluate the efficiency of the stilling basin with new types of dissipation blocks,
the experiments were conducted and the necessary measurements for each type of weir
analyzing the results and then compare it with other weir models to
applicable combination which represent in this research
dissipation ratio and hydraulic jump length ratio for each specific weir.
riangular cutting angle for dissipation blocks (45°
, 60°
)
Horizontal cutting angle for dissipation blocks (60°
, 110°
)
Dimensions and specifications of the energy dissipation blocks used in the study
Angle of
Cutting
45°
60°
60°
110°
60°
110°
evaluate the efficiency of the stilling basin with new types of dissipation blocks,
of weir notches were
models to find out
which represent in this research energy

(C): Vertical cutti
Figure (3): View pictures for basins used in this study
The general method adopted for sequencing all
same steps in each experiment by installing the dissipation bloc
certain distance between the blocks based on the recommendations of the U.S. Bureau of
Reclamation USBR (Water Measurement Manual, 2001
them on the floor of the channel at a
certain discharge, measurements were
following measurements were taken for all tests conducted on different groups of
1-Measuring the discharge passing in the channel.
2- Measure the water level over compound
3- Measure the depth of flow after hydraulic jump directly.
4- Measure the average depth of flow after the end of the hydraulic jum
5- Measure the length of the hydraulic jump (L
6- Measure the length of the hydraulic jump roller (L
Then the following calculations were
1- Calculate the initial velocity of flow (v
continuity equation:
fA
Q
v ====
In which;
v= velocity of flow (L/T).
Q=discharge (L3
/T).
Af=area of water way(L2
).
2- Calculate the primary Froude Number
following equation:
Vertical cutting angle for dissipation blocks (60°
, 110°
)
View pictures for basins used in this study
method adopted for sequencing all experiments, was performed by repeats the
same steps in each experiment by installing the dissipation blocks on a glass plate and organizes a
Water Measurement Manual, 2001) to simulate stilling basin, and then install
the floor of the channel at a distance from the nape of compound weir. Thereafter passing
were taken and new discharge was released, and so on;
following measurements were taken for all tests conducted on different groups of dispassion blocks:
easuring the discharge passing in the channel.
compound weir notch (Y1) by using point gage.
hydraulic jump directly.
Measure the average depth of flow after the end of the hydraulic jump directly (Y
Measure the length of the hydraulic jump (Lj).
Measure the length of the hydraulic jump roller (Lr).
Then the following calculations were performed:
Calculate the initial velocity of flow (v1) through weir notch and subsequent ve
….. [1]
Froude Number (Fr1), and subsequent Froude Number
was performed by repeats the
ks on a glass plate and organizes a
to simulate stilling basin, and then install
Thereafter passing a
new discharge was released, and so on; the
dispassion blocks:
p directly (Y2).
) through weir notch and subsequent velocity (v2) via
Froude Number (Fr2) from the

38
gD
v
Fr ==== ….. [2]
In which;
g= the acceleration due to gravity (L/T2
).
D=hydraulic depth (L).
3- Based on energy relationships, the general relationship for the flow energy dissipation can be
verified, applying energy equations between two sections upstream and downstream weir, we get:
g
v
YE
2
2
1
11 ++++==== ….. [3]
g
v
YE
2
2
2
22 ++++==== ….. [4]
In which;
E1= flow energy upstream weir (L).
E2= flow energy downstream hydraulic jump (L).
v1,v2= velocity upstream weir and downstream hydraulic jump respectively (L/T).
Y1=water depth over weir notch (L).
Y2=water depth downstream hydraulic jump (L).
3. RESULTS AND DISCUSSION
3.1 Effect of Using Energy Dissipation Blocks on the Relative Energy Dissipation
The results concerning the energy dissipation ratio (E2/E1) were plotted against primary
Froude Number (Fr1) for all compound weir notches used in the present study, as shown in figures
(4-11). Figure (4) shows the obtained energy dissipation ratio (E2/E1) computed at downstream of the
hydraulic jump for different types of energy dissipation blocks for compound weirs of half circle
lower notch (radius of 10cm).The obtained relative energy dissipation ratio varies between
(64.574%) at maximum discharge of (11.20ℓ‫ݏ݌‬ሻ and (66.418%) at minimum discharge of (3.0 ℓ‫ݏ݌‬ሻ
for triangular cutting block with (θ=45°
). The relative energy dissipation ratio (E2/E1) increased as
(Fr1) increased roughly for all types of dissipation blocks.
Figure (5) shows that largest average value for (E2/E1) was (62.172%) when using a
triangular cut blocks of (θ=45°
) for all discharge values between (3.80 to 11.11 ℓ‫ݏ݌‬). Whereas the
relative energy dissipation ratio (E2/E1) decreased rapidly for increased (Fr1), almost for all types of
energy dissipation blocks, this was due to high turbulence and eddies were clear at the basin bed and
the flow surface, especially at high discharges when using horizontal and vertical cut angle blocks
were much higher compared to that of triangular cut blocks.

39
Figure (4): Energy dissipation ratio for compound weir having (R=10cm) lower half-circle
notch
Figure (5): Energy dissipation ratio for compound weir having (R=5cm) lower half-circle notch
Figures (6&7) summarizes the obtained values of the relative energy dissipation ratio (E2/E1)
and Froude Number (Fr1) for compound weir having (60°) and (90°) lower V-notches respectively.
The relative energy dissipation ratio (E2/E1) was decreased rapidly with a small difference versus the
increase of (Fr1) for the initial discharge rates (i.e., Fr1 values between 0.5 to 1.0) for the weir having
lower V-notch (60°), whereas (E2/E1) values were increased significantly when (Fr1) was increased
beyond prescribed range. The minimum average value of (E2/E1) was (44.519%) which was recorded
for a blocks of vertical angle of (θ=60°
) as shown in figure (6). For all applied discharge values, the
relative energy dissipation ratio (E2/E1) was decreased as (Fr1) increased (see figure 7), the average
value of (E2/E1) was about (59.167%-55.793%) for all blocks types with a reduction of (E2/E1)
average values of (13.435%-11.274%) for compound weir having(90°) lower V-notch.
0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6
Fr1
50
55
60
65
70
75
80
85
E2/E1
Energy Dissipation Blocks
θ=60
θ=45
θ=60
θ=110
θ=60
θ=110
Triangular Cut
Blocks
Horizontal Angle
Blocks
Vertical Angle
Blocks
0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2
Fr1
40
45
50
55
60
65
70
75
80
E2/E1
θ=60
θ=45
θ=60
θ=110
θ=60
θ=110
Triangular Cut
Blocks
Horizontal Angle
Blocks
Vertical Angle
Blocks

40
Figure (6): Energy dissipation ratio for compound weir having 60° lower V-notch
Figure (7): Energy dissipation ratio for compound weir having 90° lower V-notch
Figures (8&9) show the variation of the relative energy dissipation ratio (E2/E1) and the
primary Froude Number with the applied discharges for compound weir having (30°) and (90°)
lower trapezoidal notches respectively. Figure (8) indicates there was a slight decreasing for high
discharges. On the other hand, there was no clear change in relative energy dissipation ratio (E2/E1)
between different configurations of blocks especially at the low discharges, i.e., the average value of
(E2/E1) was about (53.943%-51.056%) for all blocks types. Figure (9) shows that flow through
compound weir having (90°) lower trapezoidal notch, and along dissipation blocks during the
experimental runs at the same discharges have the same hydraulic characteristics of the flow that was
described for figure(8) above. But with high rate of energy dissipation ratio (E2/E1) which was about
(70.228%) at the maximum discharge of (11.0 ℓ‫ݏ݌‬ሻ.
0.45 0.60 0.75 0.90 1.05 1.20 1.35 1.50
Fr1
30
35
40
45
50
55
60
65
70
E2/E1
θ=60
θ=45
θ=60
θ=110
θ=60
θ=110
Triangular Cut
Blocks
Horizontal Angle
Blocks
Vertical Angle
Blocks
0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60
Fr1
40
45
50
55
60
65
70
75
80
85
90
E2/E1
θ=60
θ=45
θ=60
θ=110
θ=60
θ=110
Horizontal Angle
Blocks
Vertical Angle
Blocks
Triangular Cut
Blocks

41
Figure (8): Energy dissipation ratio for compound weir having 30° lower trapezoidal notch
Figure (9): Energy dissipation ratio for compound weir having 90° lower trapezoidal notch
Figures (10&11) show the variation of the relative energy dissipation ratio (E2/E1) and the
primary Froude Number with the applied discharges for compound weir having (2-steps) and (3-
steps) lower notches respectively. The obtained values of (E2/E1) at high discharge with (2-steps)
compound weir were less than that of smaller discharges for all blocks configurations. The maximum
(E2/E1) of (68.859%) for a blocks of triangular cut with angle (θ=60°
). While, for the rest blocks
configurations there were a slight differences at all discharges values with a relative difference of
about 1.46 % as shown in figure (10). The relative energy dissipation ratio (E2/E1) versus Froude
Number (Fr1) during the experimental runs at all applied discharges for (3-steps) compound weir was
shown in figure (11), the average values of (E2/E1) were about (62.289%) for a blocks of triangular
cut with (θ=45°
) to (59.884%) for a block of vertical angle with(θ=60°
).
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2
Fr1
40
45
50
55
60
65
70
75
80
85
E2/E1
θ=60
θ=45
θ=60
θ=110
θ=60
θ=110
Triangular Cut
Blocks
Horizontal Angle
Blocks
Vertical Angle
Blocks
0.4 0.6 0.8 1.0 1.2 1.4 1.6
Fr1
15
25
35
45
55
65
75
E2/E1
θ=60
θ=60
θ=60
θ=110
θ=60
θ=110
Triangular Cut
Blocks
Horizontal Angle
Blocks
Vertical Angle
Blocks

42
Figure (10): Energy dissipation ratio for compound weir having (2-steps) lower notch
Figure (11): Energy dissipation ratio for compound weir having (3-steps) lower notch
3.2 Effect of Using Energy Dissipation Blocks on the Hydraulic Jump and Roller Length
To investigate the effects of using the energy dissipation blocks upon the hydraulic jump
location, relative reduction in hydraulic jump length, and length of roller (or recirculation zone) of
hydraulic jump for all compound weir notches used in the present study, the results obtained herein
were plotted as shown in figures (12-19). Figure (12) shows that minimum average value for relative
hydraulic jump length (Lj/Y2) was (5.271) when using a blocks of triangular cut of (θ=45°
) for all
discharge values between (3.0 to11.2 ℓ‫ݏ݌‬). The relative hydraulic jump length (Lj/Y2) increases
slightly as Froude Number (Fr1) increases for all types and configurations of energy dissipation
blocks when using the compound weir having (R=10cm) lower half-circle notch. . Figure (13) shows
that at maximum applied discharge, the hydraulic jump was formed at shorter distance from the
compound weir having (R=5cm) lower half-circle notch with (Lj/Y2) of (5.191) when using blocks of
triangular cut with (θ=45°
), while for vertical angle cut with (θ=60°
) the hydraulic jump was formed
0.7 0.8 0.9 1.0 1.1 1.2 1.3
Fr1
48
51
54
57
60
63
66
69
E2/E1
θ=60
θ=45
θ=60
θ=110
θ=60
θ=110
Triangular Cut
Blocks
Horizontal Angle
Blocks
Vertical Angle
Blocks
0.6 0.7 0.8 0.9 1.0 1.1 1.2
Fr1
60.0
63.0
66.0
69.0
72.0
75.0
78.0
E2/E1
θ=60
θ=45
θ=60
θ=110
θ=60
θ=110
Triangular Cut
Blocks
Horizontal Angle
Blocks
Vertical Angle
Blocks

43
0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4
Fr1
0
5
10
15
20
25
30
35
Lj/Y1
θ=60
θ=45
θ=60
θ=110
θ=60
θ=110
Triangular Cut
Blocks
Horizontal Angle
Blocks
Vertical Angle
Blocks
at longer distance from the weir with (Lj/Y2) of (16.125). For all types of dissipation blocks the
(Lj/Y2) decreases as (Fr1) increased within the range of applied discharges.
Figure (12): Hydraulic jump length ratio for compound weir having (R=10cm) lower half-circle
notch
Figure (13): Hydraulic jump length ratio for compound weir having (R=5cm) lower half-circle notch
Figure (14) shows the variation of relative hydraulic jump length (Lj/Y2) and the Froude
Number (Fr1) with applied discharge for a compound weir having (60°) lower V-notch, (Lj/Y2) was
decreased significantly versus the increase of (Fr1) for values between (0.4 to 1.0), whereas (Lj/Y2)
values increased when (Fr1) was increased for higher discharge values. The hydraulic jump was
occurred at shorter distance from the compound weir when the value of (Lj/Y2) was (5.359) which
recorded for a blocks of triangular cut with angle of (θ=45°
). For all applied discharge values, the
relative hydraulic jump length (Lj/Y2) were decreased as (Fr1) increased as shown in figure (15), the
shortest and longest distance in which the hydraulic jump formed within stilling basin length were
0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2
Fr1
0
3
6
9
12
15
18
21
24
27
30
33
Lj/Y1
θ=60
θ=45
θ=60
θ=110
θ=60
θ=110
Triangular Cut
Blocks
Horizontal Angle
Blocks
Vertical Angle
Blocks

44
about (4.794) for a blocks of triangular cut angle with (θ=45°
) and (8.917) for a blocks of horizontal
cut angle with (θ=110°
) respectively.
Figure (14): Hydraulic jump length ratio for compound weir having 60° lower V-notch
Figure (15): Hydraulic jump length ratio for compound weir having 90° lower V-notch
Figures (16 & 17) show the variation of the relative hydraulic jump length (Lj/Y2) and the
Froude Number(Fr1) with the all applied discharge range for compound weir having (30°) and (90°)
lower trapezoidal notches respectively. Figure (16) shows there was a rapidly decreasing in (Lj/Y2)
as (Fr1) increase within the limits of lower and moderate flow rates for all blocks types. There were
small differences in relative energy dissipation ratio (Lj/Y2) between various configurations of blocks
especially at the low discharges; the average value of (Lj/Y2) was about (6.314) for a blocks of
triangular cut angle with (θ=45°
) to (8.616) for a blocks of horizontal angle with (θ=110°
).
0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9
Fr1
2
4
6
8
10
12
14
16
Lj/Y1
Energy Dissipation locks
θ=60
θ=45
θ=60
θ=110
θ=60
θ=110
Triangular Cut
Blocks
Horizontal
Angle Blocks
Vertical
Angle Blocks
0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70
Fr1
2.0
3.5
5.0
6.5
8.0
9.5
11.0
12.5
14.0
15.5
Lj/Y1
Energy Dissipation locks
θ=60
θ=45
θ=60
θ=110
θ=60
θ=110
Triangular Cut
Blocks
Horizontal
Angle Blocks
Vertical
Angle Blocks

45
Figure (16): Hydraulic jump length ratio for compound weir having (30°) lower trapezoidal notch
Figure (17) shows that flow through compound weir having (90°) lower trapezoidal notch,
it’s clear that (Lj/Y2) decreased as (Fr1) increase within applied discharge range for all blocks types
used in the present study, maximum reduction in relative hydraulic jump length (Lj/Y2) of (5.916)
occurred when using a blocks of triangular cut with (θ=60°
), while the minimum reduction of (8.698)
for a blocks of vertical cut angles with (θ=60°
). Generally, there were slight differences on the
reduction of relative hydraulic jump length (Lj/Y2) at low discharges for all blocks types and
configurations.
Figure (17): Hydraulic jump length ratio for compound weir having (90°) lower trapezoidal notch
Figures (18 & 19) show the variation of the relative hydraulic jump length (Lj/Y2) and the
Froude Number (Fr1) with the all applied discharge range for compound weir having (2-steps) and
(3-steps) lower notches respectively. From figure (18) it is clear that relative hydraulic jump length
(Lj/Y2) decreases significantly as Froude Number (Fr1) decreases for all blocks types. At maximum
0.40 0.55 0.70 0.85 1.00 1.15 1.30 1.45 1.60
Fr1
0
2
4
6
8
10
12
14
16
18
Lj/Y2
θ=60
θ==45
θ=60
θ=110
θ=60
θ=110
Triangular Cut
Blocks
Horizontal
Angle Blocks
Vertical
Angle Blocks
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2
Fr1
0
2
4
6
8
10
12
14
16
18
Lj/Y2
θ=60
θ==45
θ=60
θ=110
θ=60
θ=110
Triangular Cut
Blocks
Horizontal
Angle Blocks
Vertical
Angle Blocks

46
applied discharge of (10.5ℓ‫ݏ݌‬), the relative hydraulic jump length (Lj/Y2) was (12.576) for a blocks
of vertical cut angle with (θ=60°
), with a free hydraulic jump at a distance (83.0 cm) forward the
weir. The shortest average value of (Lj/Y2) of (5.374) formed when using blocks of triangular cut
angle with (θ=60°
).
Figure (18): Hydraulic jump length ratio for compound weir having (2-steps) lower notch
Figure (19) makes clear that for a compound weir having (3-steps) lower notch, the (Lj/Y2)
decreased slightly as (Fr1) increased, and occurred through all applied discharges range. The
hydraulic jump occurs at shorter distances measured from the compound weir when using blocks of
triangular cut angle with (θ=45°
) in which the average value of (Lj/Y2) was (5.933).
Figure (19): Hydraulic jump length ratio for compound weir having (3-steps) lower notch
0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3
Fr1
0
2
4
6
8
10
12
14
16Lj/Y1 Energy Dissipation Blocks
θ=60
θ=45
θ=60
θ=110
θ=60
θ=110
Triangular Cut
Blocks
Horizontal
Angle Blocks
Vertical
Angle Blocks
0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 1.25
Fr1
0
2
4
6
8
10
12
14
16
18
20
Lj/Y1
θ=60
θ=45
θ=60
θ=110
θ=60
θ=110
Triangular Cut
Blocks
Horizontal
Angle Blocks
Vertical
Angle Blocks

Figures (20-22) show the flow through the compound weir models and along the various
configurations of energy dissipation blocks, and the hydraulic jump formation d
experimental runs at the applied discharges. High eddies and air entrainment occurred at the bed of
channel when the energy dissipaters were used especially at high discharges. Then, more energy will
be dissipated. A free hydraulic jump was form
distance according to the flow rate and the configuration. The hydraulic jump occurs at shorter
distances measured from the weir front when using energy dissipation blocks in all of the applied
discharges. Table (3) summarizes the average values of the primary Froude Number (Fr
relative jump roller length (Lr/∆Y) that were obtained at the applied discharge range.
(a) Arrangement of blocks with horizontal
cut angle
Figure (20): Flow along dissipation blocks for compound weir having half circle lower notch
(a) Arrangement of blocks with triangular
cut angle
Figure (21): Flow along dissipation blocks for compound weir having stepped lower notch
) show the flow through the compound weir models and along the various
configurations of energy dissipation blocks, and the hydraulic jump formation d
be dissipated. A free hydraulic jump was formed at the downstream of the weir at a different
(3) summarizes the average values of the primary Froude Number (Fr
Y) that were obtained at the applied discharge range.
horizontal (b) Arrangement of blocks with vertical
cut angle
Flow along dissipation blocks for compound weir having half circle lower notch
(a) Arrangement of blocks with triangular (b) Arrangement of blocks with vertical
cut angle
Flow along dissipation blocks for compound weir having stepped lower notch
) show the flow through the compound weir models and along the various
configurations of energy dissipation blocks, and the hydraulic jump formation during the
ed at the downstream of the weir at a different
(3) summarizes the average values of the primary Froude Number (Fr1), and
Y) that were obtained at the applied discharge range.
blocks with vertical
angle
Flow along dissipation blocks for compound weir having half circle lower notch
nt of blocks with vertical
Flow along dissipation blocks for compound weir having stepped lower notch

(a) Arrangement of blocks with horizontal
cut angle
Figure (22): Flow along dissipation blocks for compound weir having lower V
Table (3): Summary of obtained average values of (Fr
configurations used in this study
Type of Dissipation Blocks
Blocks of triangular cut angle:
Configuration(A):
θ=45°
Configuration(B):
θ=60°
Rectangle with lower
half circle notch
Rectangle with lower V
notch
trapezoidal notch
Rectangle with stepped
lower notch
Blocks of horizontal cut
angle:
Configuration(A): θ=60°
Configuration(B): θ=110°
half circle notch
notch
Rectangle wi
trapezoidal notch
lower notch
Blocks of vertical cut angle:
Configuration(A): θ=60°
Configuration(B): θ=110°
half circle notch
notch
trapezoidal notch
lower notch
(a) Arrangement of blocks with horizontal (b) Arrangement of blocks with vertical
cut angle
Flow along dissipation blocks for compound weir having lower V
Summary of obtained average values of (Fr1), and roller length (Lr/∆Y) for all blocks and
configurations used in this study
Weir Model
(θw= Weir angle)
Discharge
Range
( )
(Fr1
(A)
half circle notch
R=5,10cm
3.1-11.9 0.80 0.78
3.1-11.9 1.17 1.08
Rectangle with lower V-
θθθθw=60°°°°
, 90°°°° 3.1-11.1 0.82 0.84
3.3-11.1 0.46 0.50
ezoidal notch θθθθw=30°°°°
, 90°°°° 3.1-11.1 0.67 0.74
3.2-11.6 0.67 0.74
lower notch
2,3 steps
3.3-10.5 0.79 0.83
2.9-11.6 0.85 0.87
half circle notch
R=5,10cm
3.1-11.9 1.32 1.14
3.1-11.9 1.13 1.08
, 90°°°° 3.1-11.1 1.07 1.15
3.3-11.1 0.50 0.49
trapezoidal notch θθθθw=30°°°°
, 90°°°° 3.1-11.1 0.66 0.68
3.2-11.6 0.75 0.67
lower notch
2,3 steps
3.3-10.5 0.82 0.87
2.9-11.6 0.94 0.93
half circle notch
R=5,10cm
3.1-11.9 1.42 1.16
3.1-11.9 1.24 1.09
, 90°°°° 3.1-11.1 0.86 0.92
3.3-11.1 0.46 0.44
trapezoidal notch θθθθw=30°°°°
, 90°°°° 3.1-11.1 0.69 0.78
3.2-11.6 0.58 0.71
lower notch
2,3 steps
3.3-10.5 0.82 0.84
2.9-11.6 0.94 0.93
nt of blocks with vertical
Flow along dissipation blocks for compound weir having lower V- notch
Y) for all blocks and
1) (Lr/∆∆∆∆Y)
(B) (A) (B)
0.78 5.26 5.02
1.08 8.60 6.52
0.84 2.01 1.98
0.50 3.21 3.03
0.74 2.78 3.32
0.74 5.95 5.94
0.83 7.24 10.47
0.87 5.18 5.70
1.14 8.63 8.80
1.08 8.63 9.16
1.15 2.22 2.19
0.49 3.40 3.67
0.68 3.40 3.73
0.67 7.50 7.96
0.87 7.31 9.04
0.93 5.78 6.59
1.16 11.62 10.01
1.09 13.02 10.29
0.92 2.58 2.57
0.44 4.03 3.39
0.78 3.38 3.67
0.71 6.18 7.72
0.84 8.26 8.43
0.93 6.27 6.84

49
4. CONCLUSIONS
Based on the results obtained in this study, the following conclusions were achieved:
1- Arrangement containing the use of compound weir with (60°
) lower V-notch and dissipation
blocks of horizontal cutting angle configurations (60°
,110°
)were produced maximum reduction in
flow energy of (54.7% to 55.4%) respectively for all the applied range of discharge.
2- Configuration included use of compound weir with (60°
) lower V-notch and dissipation blocks of
triangular cutting angle configurations (45°
,60°
) have the smallest value of the relative hydraulic
jump length (Lj/Y2) of (5.36 to6.02) respectively for all the applied range of discharge compared
with configurations in this study.
3- The relative jump roller length (recirculation zone), with above configuration was about (1.94) at
minimum applied discharge of (3.2ℓ‫ݏ݌‬), and was about (2.14) at maximum applied discharge of
(10.3 ℓ‫ݏ݌‬) for blocks of triangular cut angle with (θ=60°
).
4- The obtained results indicate that use the configuration containing compound weir with (60°
, 90°
)
lower V-notch with all dissipation blocks have a high efficiency especially at the high discharges.
5. REFERENCES
• Giglou, A. N., Giglou, T.N., Minaei,A.,2013.” Analytical Analysis of the Hydraulic Jump Roller
Length in Open Channel”, Life Science Journal,10(6s).
• Zhou, Q., Yin, C., 2011.” The Baffle block Effect of Fluctuating pressure in hydraulic Jump with
Low Froude Number”, Multimedia Technology (ICMT), Page(s):1290–1293, IEEE Conference
Publications.
• Abdel-Aal, G. M., Negm, A.M., Owais, T.M., Habib, A.A., 2003.” Theoretical Modeling of
Hydraulic Jumps at Negative Step in Radial Stilling Basins with End Sill”, Seventh International
Water Technology Conference, Egypt.
• Irzooki,R.H., Bakir, Abd-Alsabir, I., Kadhban,I. I.,2005” Dissipation of Hydraulic Energy in
Stilling Basin by Cutting Baffle Blocks”, Tikrit Journal of Engineering Sciences,Vol.12,No.3,
ISSN: 1813162X, (in Arabic).
• Omer, K.A., Irzooki, R. H., Salah, R. A.,2008.” Drag Forces and Flow Types on Unconventional
Types of Stilling Basins Baffle Blocks”, Tikrit Journal of Engineering Sciences, Vol.15, No.3.
• Abbas, M. M., 2009,” Experimental Investigation on Makhool Dam Stilling Basin”, Diyala
Journal of Engineering Sciences, Vol. 02, No. 02, pp. 53-76, ISSN 1999-8716 (Printed in Iraq).
• Kurukji, E. M., 2012.” Experimental Study for Improving the performance of Stepped Spillway
using an Obstructions”, Al-Rafidain Engineering, Vol.20, No.1. pp. 83-93.
• Retsinis, E., Dimitriou, D., Demetriou, J., 2011.” Local Energy Change Around Sluice Gate and
Weir Flows Within Inclined Channels”, Proceedings of the 3rd
International CEMEPE &
SECOTOX Conference, Skiathos, ISBN 978-960-6865-43-5.
• Maatooq, J. S., AL-Adili, A. S., Sameen, S. S., 2013.” Relevant Problems of a Hydraulic Jump at
Diyala Weir and the Proposed Remedy”, Eng. &Tech. Journal, Vol.31, Part (A), No.13.
• United States Department of the Interior, Bureau of Reclamation, Water Resources Research
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• H. L. Tiwari, “Analysis of Baffle Wall Gap In The Design of Stilling Basin Model” International
Journal of Civil Engineering & Technology (IJCIET), Volume 4, Issue 4, 2013, pp. 66 - 71, ISSN
Print: 0976 – 6308, ISSN Online: 0976 – 6316.

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