PHYSICAL MODELING INVESTIGATION OF · PDF fileFigure (6.9) Relationship between α and...

Physical Modeling Investigation of Performance of Sediment

Vanes at Intakes

BY

Abdel Azim Mohamed Ali

Fahmy Salah Abdelhaleem

Coordinated by

Dr. Yonas Michael

Addis Ababa University

Scientific Advisor

Prof. Petru Boeriu

UNESCO-IHE

2010

Produced by the

Nile Basin Capacity Building Network

(NBCBN-SEC) office

Disclaimer

The designations employed and presentation of material and findings through the publication don’t imply the expression of any opinion

whatsoever on the part of NBCBN concerning the legal status of any country, territory, city, or its authorities, or concerning the delimitation

of its frontiers or boundaries.

Copies of NBCBN publications can be requested from:

NBCBN-SEC Office

Hydraulics Research Institute

13621, Delta Barrages, Cairo, Egypt

Email: [email protected]

Website: www.nbcbn.com

Images on the cover page are property of the publisher

© NBCBN 2010

mailto:[email protected]

http://www.nbcbn.com/

Project Title

Knowledge Networks for the Nile Basin

Using the innovative potential of Knowledge Networks and CoP’s in strengthening human and

institutional research capacity in the Nile region.

Implementing Leading Institute

UNESCO-IHE Institute for Water Education, Delft, The Netherlands (UNESCO-IHE)

Partner Institutes

Ten selected Universities and Ministries of Water Resources from Nile Basin Countries.

Project Secretariat Office

Hydraulics Research Institute – Cairo - Egypt

Beneficiaries

Water Sector Professionals and Institutions in the Nile Basin Countries

Short Description

The idea of establishing a Knowledge Network in the Nile region emerged after encouraging

experiences with the first Regional Training Centre on River Engineering in Cairo since 1996. In

January 2002 more than 50 representatives from all ten Nile basin countries signed the Cairo

Declaration at the end of a kick-off workshop was held in Cairo. This declaration in which the main

principles of the network were laid down marked the official start of the Nile Basin Capacity

Building Network in River Engineering (NBCBN-RE) as an open network of national and regional

capacity building institutions and professional sector organizations.

NBCBN is represented in the Nile basin countries through its nine nodes existing in Egypt, Sudan,

Ethiopia, Tanzania, Uganda, Kenya, Rwanda, Burundi and D. R. Congo. The network includes six

research clusters working on different research themes namely: Hydropower, Environmental

Aspects, GIS and Modelling, River Morphology, flood Management, and River structures.

The remarkable contribution and impact of the network on both local and regional levels in the basin

countries created the opportunity for the network to continue its mission for a second phase. The

second phase was launched in Cairo in 2007 under the initiative of; Knowledge Networks for the

Nile Basin. New capacity building activities including knowledge sharing and dissemination tools

specialised training courses and new collaborative research activities were initiated. The different

new research modalities adopted by the network in its second phase include; (i) regional cluster

research, (ii) integrated research, (iii) local action research and (iv) Multidisciplinary research.

By involving professionals, knowledge institutes and sector organisations from all Nile Basin

countries, the network succeeded to create a solid passage from potential conflict to co-operation

potential and confidence building between riparian states. More than 500 water professionals

representing different disciplines of the water sector and coming from various governmental and

private sector institutions selected to join NBCBN to enhance and build their capacities in order to

be linked to the available career opportunities. In the last ten years the network succeeded to have

both regional and international recognition, and to be the most successful and sustainable capacity

building provider in the Nile Basin.

1. BACKGROUND………………... .............................................................................................. 1

2. INTRODUCTION………………... ............................................................................................ 1

3. PREVIOUS RESEARCHES………………... ............................................................................ 2

3.1 Separation Zone………………... ................................................................................................ 2

3.2 Diverted Sediment………………... ............................................................................................ 5

3.3 Theory of Vanes………………... ............................................................................................... 6

4. LABORATORY EXPRIMRNTS………………... .................................................................... 9

5. EXPERIMENTAL PROCEDURE………………... ................................................................. 11

6. ANALYSIS OF EXPERIMENTAL RESULTS………………... ............................................ 15

6.1 Single Row of Vanes………………... ...................................................................................... 16

6.2 Triple Rows of Vanes………………... ..................................................................................... 28

6.2.1 Case of Using Triple Rows of Vanes at Different Angles………………... ..................... 28

6.2.2Case of Using Triple Rows of Vanes at Different Heights………………... .................... 32

6.3 Double Rows of Vanes………………... ................................................................................... 36

6.3.1 Case of Using Double Vane Rows at Different Positions .................................................. 36

6.4 Comparison Between The Considered Cases………………... ................................................. 39

7. CONCLUSIONS AND RECOMMENDATIONS………………... ......................................... 43

7.1 Recommendations………………... .......................................................................................... 44

8. BIBLIOGRAPHY………………... .......................................................................................... 44 List of Research Group Members

APPENDIX (A)

LIST OF FIGURES

Figure (3.1) Layout of the intake, [2] .................................................................................................................. 3

Figure (3.2) Layout of junction edge types (Sharp, chamfer, circular), [8]........................................................ 4

Figure (3. 3) Sediment rejection, [9] ................................................................................................................... 5

Figure (3.4) Sediment extraction, [9] .................................................................................................................. 6

Figure (3.5) Sediment ejection (vortex tube), [9] ................................................................................................ 6

Figure (3.6) Design variables of vane system, [13] ............................................................................................. 7

Figure (4.1) Flume layout .................................................................................................................................. 10

Figure (5.1) Layout of the tests Program ........................................................................................................... 12

Figure (5.2) Velocity measurements locations .................................................................................................. 14

Figure (6.1) Submerged vanes at the intake ...................................................................................................... 15

Figure (6.2) Relationship between bv/bd, and SV/SVw, for different Qr and λ-1 for single row of vanes ..... 17

Figure (6.2) Continue ........................................................................................................................................ 18

Figure (6.3) Relationship between bv/bd and ds/dsw for different Qr and λ-1 for single row of vanes ........... 19

Figure (6.3) Continue ........................................................................................................................................ 20

Figure (6.4) Relationship between α and SV/SVw, for different Qr and λ-1 for single row of vanes .............. 21

Figure (6.4) Continue ........................................................................................................................................ 22

Figure (6.5) Relationship between α and ds/dsw for different Qr and λ-1 for single row of vanes .................. 23

Figure (6.5) Continue ........................................................................................................................................ 24

Figure (6.6) Relationship between Hv/Yt, and SV/SVw, for different Qr and λ-1 for single row of vanes ..... 25

Figure (6.6) Continue ........................................................................................................................................ 26

Figure (6.7) Relationship between Hv/Yt and ds/dsw for different Qr and λ-1 for single row of vanes .......... 27

Figure (6.7) Continue ........................................................................................................................................ 28

Figure (6.8) Relationship between α and SV/SVw, for different Qr and λ-1 for triple rows of vanes .............. 29

Figure (6.8) Continue ........................................................................................................................................ 30

Figure (6.9) Relationship between α and ds/dsw, for different Qr and values of λ-1 for triple rows of vanes . 31

Figure (6.9) Continue ........................................................................................................................................ 32

Figure (6.10) Relationship between Hv/Yt and SV/SVw, for different Qr and λ-1 for triple rows of vanes .... 33

Figure (6.10) Continue ...................................................................................................................................... 34

Figure (6.11) Relationship between Hv/Yt and ds/dsw, for different Qr and λ-1 for triple rows of vanes ....... 34

Figure (6.11) Continue ...................................................................................................................................... 35

Figure (6.12) Relationship between bv/bd, and SV/SVw, for different Qr and λ-1 for double vane rows ....... 37

Figure (6.12) Continue ...................................................................................................................................... 37

Figure (6.13) Relationship between bv/bd and ds/dsw for different Qr and λ-1 for double vane rows ............ 38

Figure (6.13) Continue ...................................................................................................................................... 39

Figure (6.14) Relationship between Qr , and ds/dsw, for different cases of vane rows and λ-1 ....................... 40

Figure (6.15) Relationship between Qr, and Sv/SVw, for different cases of vanes and λ-1 ............................. 41

Figure (6.16) Continue ...................................................................................................................................... 42

Figure (6.17) Relationship between Qr, and vr/vL, ........................................................................................... 42

LIST OF PHOTOS

Photo (4.1) Flume during construction .............................................................................................................. 11

Photo (5.1) Submerged vanes ............................................................................................................................ 12

Photo (5.2) The groups of the experimental tests .............................................................................................. 13

Photo (5.3) The used measuring devices ........................................................................................................... 14

Photo (5.4) The used measuring devices ........................................................................................................... 15

This report is one of the final outputs of the research activities under the second phase of the Nile Basin Capacity Building

Network (NBCBN). The network was established with a main objective to build and strengthen the capacities of the Nile basin

water professionals in the field of River Engineering. The first phase was officially launched in 2002. After this launch the

network has become one of the most active groupings in generating and disseminating water related knowledge within the Nile

region. At the moment it involves more than 500 water professionals who have teamed up in nine national networks (In-country

network nodes) under the theme of “Knowledge Networks for the Nile Basin”. The main platform for capacity building adopted

by NBCBN is “Collaborative Research” on both regional and local levels. The main aim of collaborative research is to strengthen

the individual research capabilities of water professionals through collaboration at cluster/group level on a well-defined

specialized research theme within the field of River and Hydraulic Engineering.

This research project was developed under the “Cluster Research Modality”. This research modality is activated through

implementation of research proposals and topics under the NBCBN research clusters: Hydropower Development, Environmental

Aspects of River Engineering, GIS and Modelling Applications in River Engineering, River Morphology, flood Management, and

River structures.

This report is considered a joint achievement through collaboration and sincere commitment of all the research teams involved

with participation of water professionals from all the Nile Basin countries, the Research Coordinators and the Scientific Advisors.

Consequently the NBCBN Network Secretariat and Management Team would like to thank all members who contributed to the

implementation of these research projects and the development of these valuable outputs.

Special thanks are due to UNESCO-IHE Project Team and NBCBN-Secretariat office staff for their contribution and effort done

in the follow up and development of the different research projects activities.

This report is based on the studies made at HRI. The main authors are Dr. Abdelazim Mohamed Ali

and Eng. Fahmy Salah Abdelhaleem, both researchers, at Hydraulics Research Institute, Egypt.

However, the material has been discussed by using the collaborative platform of the NBCBN

network and the suggestions and the contribution of the members of the research team are

acknowledged. Moreover, the study was used as an effective tool to introduce the use of the scale

studies for clarifying complex flow problems in and around the hydraulic structures. A special role in

this activity has been played by Dr. Abdel Azim by disseminating his experience and knowledge to

all members of the research team.

Symbol Definition

A Cross sectional area [L2]

bm Main channel width [L]

bd Intake channel width [L]

bv Distance from the centreline of the intake to the centreline of vane's row [L]

d50 Median grain size of sediment [L]

ds Maximum scour depth in the front of the intake [L]

dsw Maximum scour depth in the front of the intake without submerged vanes [L]

Fr Froude number of the main channel [ - ]

g Acceleration due to Gravity [L/T2]

Hv Vane height above the bed [L]

Lv Vanes length [L]

N Number of vanes in each row [ - ]

Qm Discharge passing through the main channel [L3/T]

Qd Discharge passing through the intake channel [L3/T]

Qr Discharge ratio = Qd/Qm [ - ]

SV Volume of sediment entering the intake channel [L3]

SVw Volume of sediment entering the intake channel in case of no vanes [L3]

vr Flow velocity beside the right wall of the intake channel [L/T]

vL Flow velocity beside the left wall of the intake channel [L/T]

δv Distance between two vanes in the normal direction of flow [L]

δs Distance between two rows s in the direction of flow [L]

River Structure Research Cluster 2010

Nile Basin Capacity Building Network ( NBCBN ) 1

1. BACKGROUND

Sediment deposition at the entrance of river intake structures is an important problem. In case of power-plants

that use river-cooling water, sediment deposition reduces the withdrawn capacity, causes damages to the

pumping system and causes partial or full blockage of the intake. Sediment blockage may cause stopping of

the plant. Submerged vanes are simple structures that can be used to control the sediment and redistribute the

flow and the sediment in open channels. An experimental study to minimize the sediment that enters the

intake channel using submerged vanes is investigated. Three hundred experimental runs were carried out

considering various heights, angles, and positions of the submerged vanes with different flow conditions. The

case of flat floor without vanes is included to estimate the influence of using the submerged vanes on

sediment control. Submerged vanes technique proved to have a good influence in diverting the sediment

away. The design parameters for submerged vanes were determined in order to be applicable in actual

projects.

2. INTRODUCTION

The control of sediment movement and the need for clear sediment water at the water intake is one of the most

difficult problems encountered by river engineers. Many techniques were tested over the years to mitigate the

sedimentation problems, (i.e. wing dams, jetties, dikes, and dredging). Most of these techniques are

comprehensive and expensive, while periodic dredging is still the most common solution. Cleaning the intake

entrance by dredging is not always a desirable solution not only because of cost but also because of the

difficulty in finding the suitable disposal sites or adequate mechanical tools.

Submerged vanes were defined by Odgaard, as a low aspect ratio (height-length ratio) flow-training structure

mounted vertically on the riverbed at small angles to the prevailing flow. The vanes aim to generate a

secondary circulation in the main flow, and are designed to modify the near bed flow pattern and to distribute

the flow and sediment transport within the channel cross-section. When the approach flow attacks the vane, a

high-pressure zone forms at the upstream face and a low-pressure zone forms at the downstream face. The

pressure difference across the vane induces a current over the top of the vane, which is carried downstream as

a helicoidal vortex. The helicoidal vortex is responsible for the changes in the near-bed velocity, shear stress,

and the bed topography in the vicinity of the vanes. The resulting vortices (vortex sheet), at the trailing edge

of the vane, roll up from a large vortex (springing from apposition near the top of the vane). This vortex (tip

vortex), is carried with the flow downstream, where it rises to a secondary or helical motion of the flow and is

associated with changes in the bed shear stress and the bed topography. As a result, the riverbed aggrades at

one portion of the channel cross section and degrades at another place.

The main applications of submerged vanes are erosion control, channel cross section maintenance, adjusting

the stream direction and creating new bed morphology. The most important application of submerged vanes is

in water intakes that adjust the flow and sediment patterns in the entrance of the intake. When a number of

vanes are set in each row regularly; the created vortex is due to current. This current creates some changes in

the bed shear stress and in the topography of the streambed.

This study was initiated in order to minimize the sedimentation problems at the intake channels, using the

submerged vanes technique. Many researchers had performed studies to investigate the sedimentation

phenomena and submerged vanes. However, the available literature is not enough to give an exact relation

between the intake dimensions and the vanes characteristics.

The effective parameters that are considered are:-

Positions of vanes with respect to the intake channel,

Vanes height,



Angle of vanes with the main flow direction,

Number of vane rows,

Main flow and the diverted flow discharges, and

Tail water depth of the main channel.

3. PREVIOUS RESEARCHES

The literature review of the previously published materials relevant to the research topic discussed highlighted

the following problems:

3.1- Separation Zone,

3.2- Diverted Sediment, and

3.3- Theory of vanes.

A brief discussion of these issues will be presented subsequently.

3.1 Separation Zone

Ashok S. and K Keshava, [5], developed a two dimensional numerical model for the prediction of flow

in open channel diversion. The model employed the depth average form of momentum and continuity

equations. The model performed well in predicting the discharge distributions and computed water surface

profiles, depth- average velocity distribution in the main channel, and size of separation zone that matched

fairly with the experimental observations. Their model showed that, the energy losses in open channel

diversion were similar to those observed in close conduits, when the submerged flow condition in branch

channel prevails. Their model appears to be adequate for analysing the flow in open channel diversions for

engineering design purposes.

Rashwan, I. and Tarek, A. [15], developed a theoretical model for division of flow through 90o open

channel junction over a horizontal bed for subcritical steady flow through main, extension and branch

channels of equal widths. The developed model was derived with the aid of momentum, energy and continuity

equations. The model was verified with experimental data from the previous studies and was in good

accordance with them. It was also found that a linear relationship between the experimental data of the inflow

water depth and the branch water depth existed. The specific heads upstream and downstream the junction,

were found to be practically equal.

The Uttar Pradesh Irrigation Research Institute, (UPIRI), Arved J., [4], found in practice a significant

decrease in sediment diversion if the diversion angle is more than 90o. An optimum angle for minimum

sediment diversion was found to be between 105 o -110 o.

Amin, A., [2], investigated experimentally the velocities distribution at diversions using a fixed-bed

model. He defined the effect of the diversion angles on minimizing sediment deposition in intake channels,

figure (3.1). The experimental results showed that:-

The recommended range of the diversion angles of the channel intake needed to enhance the flow pattern

inside the channel intake is in the range of 100o to 112 o.

The effect of the diversion angle of the intake channel was found to be fine in the discharge ratio range of

0.15 to 0.4, and width ratio, Br of 0.13.

The effect of the diversion angle was found to be limited in the discharge ratios range of 0.08 to 0.36 and

width ratio, Br ≥ 0.29.



Figure 3.1: Layout of the intake, [2]

In addition, he developed two empirical formulae to help the designers of intakes. His formulae were

verified in the predictions of sedimentation problems at two locations along the Nile River, and were in

accordance with the measured quantities.

Amin, recommended that, the influence of the sediment exclusion measures (such as bottom vanes

upstream the entrance of the channel intake), should be further investigated.

Helal, E. Y., [8], investigated numerically and experimentally how to minimize the effect of the

separation zone at open channel junction. This could be achieved by changing the downstream edge of the

junction from sharp to chamfer to circular edge, figure (3.2). Experimental runs were categorized according to

the junction and bed types. He measured the water depths, velocity along the profile, maximum scour depths,

and scour-hole lengths.

In the numerical study, the finite element technique was implemented in order to determine the

velocity distribution downstream the junction with different dimensions, using ANSYS software program.

The main factors, that were considered, were the main and branch channel velocities and radius of circular

edge. The numerical runs were categorized into two groups, the first one was a sharp edged junction, and the

others were circular edge radius. It was concluded that:

The circular edge radius reduced the scour depths and the separation zone width with a reduction

factor of 85% and 47%, respectively compared to the case of a sharp edged junction.

No separation zones downstream the junction occurred when a circular edge radius of 1.33 of the

main channel bed width was used.

Qm Bm

Bd

Qd θ

Main Channel

Intake

channel Inner wall

Outer wall



Figure 3.2: Layout of junction edge types (Sharp, chamfer, circular), [8]

a- Case of sharp edge with fixed bed

downstream cornerUpstream Corner

Main ChannelBmu

tB

Tirbtary Channel

Main ChannelBmd

b- Case of chamfer edge with fixed bed

mu

Upstream Corner

Main ChannelB

mL

tBLt

mdBMain Channel

Tirbtary Channel

c- Case of circular edge with fixed bed

mu

Tirbtary Channel

Main ChannelB

Upstream Corner tB

BmdMain Channel

R



3.2 Diverted Sediment

The separation of bed-load sediment from the water is somehow easier to handle than excluding of

sediment in suspension. There are numerous methods and techniques to do this. These are all based on a

single principle, namely the application of a horizontal division separating the upper layers containing mostly

pure water from the lower layers that carry sediment. Many techniques were studied over the years to mitigate

the problem, Helmut, S., and Felix M., [9], among them are to:

Reject the sediment by means of sills and bars using spur dykes or training walls, Extract the sediment by

means of sediment tunnels and flushing devices, and

Eject the sediment by means of vortex tube sediment ejectors.

Principle of sediment rejection: The upper layers of the flow are allowed to enter the intake; the lower layers

are prevented from entering the intake and conveyed towards downstream with the remaining river flow.

Submerged sills, bars, and submerged vanes can use for this purpose. The sediment rejection technique can

allow diverting up to 50% of the total river flow without bed load problems at the intake. For optimum

efficiency of the sediment rejection technique, the design should be supported by hydraulic model tests, figure

(3.3).

Principle of sediment extraction: The separation of water and sediment is achieved by dividing the flow in

an upper and in a lower part by means of a horizontal apron. The upper part containing pure water is diverted

according to the purpose of the scheme; the lower part containing the sediment is conveyed downstream by

means of sediment tunnels and permanently operated flushing gates. For the application of this method the

existence of a diversion dam is compulsory in order to provide the necessary pressure difference for flushing.

Under favourable conditions (optimum design and correct operation) the sediment extraction technique can

reach great efficiency, figure (3.4).

.

Figure 3. 3: Sediment rejection, [9]



Figure 3.4: Sediment extraction, [9]

Principle of sediment ejection (vortex tube): Due to gravity and the momentum of the water entering the tube

underneath the slot, the sediment moving in the lower layers enters the tube. The tube consists of a pipe with a

slit on its crown laid at an angle between 45° to 90° relative to the flow direction. The top of the pipe is laid

flat with the canal bottom. The action of changing direction following the pipe wall curvature as soon as the

water enters the pipe creates a vortex effect which keeps the entering particles longer in suspension. The

hydraulic energy slope between the canal water level and the pipe outlet axis causes water to flow out of the

tube laterally stretching the swirl flow down the pipe, figure (3.5).

Figure 3.5: Sediment ejection (vortex tube), [9]

The most famous example of the sediment rejection technique was the submerged vanes. The

submerged vanes technique is used for solving the sediment problems at a number of water intakes. One

example is the intake of El-Kurimat power station. Kurimat power station is located on the east side of the

Nile River, 811Km downstream Aswan High Dam, Egypt.

3.3 Theory of Vanes

Odgaard, A.J., and Wang Y., [13], developed the design basis of the vane technique. Briefly vane

parameters are given on figure (3.6), (i.e. initial vane height, Ho, ratio of vane height to vane length, Ho/L,

angle of incidence, vane submergence, T, longitudinal and transverse vane spacing, δs, and δn, and distance

between outermost vane and bank, δb).



The flow and sediment parameters represented are:

Pre-vane cross-section averaged flow depth, do [L]

Flow velocity, uo [L/T ]

Resistance parameter, m = fk /8 , where; [-]

f = the Darcy-Weisbach friction factor, and k = Karman constant [-]

Ratio of channel width to depth b/ do [-]

Ratio of channel width to radius of curvature b/ r [-]

Sediment Froude number FrD = gDuo

/ [-]

where; D = median grain diameter [L]

Figure 3.6: Design variables of vane system, [13]

In general, theory of Odgaard, solved the equations of motion of water and sediment (using appropriate

boundary conditions), to obtain flow and depth distributions in the channel. The equations include terms that

accounted for the vane-induced bed-shear stress using the airfoil theory. The vane-induced bed shear stresses

are functions of the above mentioned vane characteristics and an increase of any of these vane parameters

causes the changes in the bed channel elevation to increase. For fully developed flow at the equilibrium state

Sadjedi Sabegh M., et al, [16], investigated experimentally the mechanism of sedimentation in the

entrance of delivery channel and studied the role of submerged vanes in preventing sedimentation in the



delivery channel of flood distribution system. The used physical model was based on the practical problem of

sedimentation in the intake of Bishe-zard River (one of the Iranian rivers in Fars province). The model was

made in a laboratory flume 2.5 m wide and 30 m long and with a diversion channel 1.3 m wide and Sediment

diameter of 3.4 mm. The main investigated parameters were discharge and submerged vanes array, the

longitudinal distance between two successive row of vanes, the across distance of vanes, number of vanes in

each row, total number of vanes and height of vanes.

They concluded that, in the three vanes orientation the best result was obtained when the distance of

inner vanes from the channel wall was 3h (h is the vane height), and the distance between the other two vanes

in each row was 2h. For vanes with zigzag form, when the inner distance was 1h and the across distance

between vanes was 3h, the best solution was obtained. Also they mentioned that, with using three vanes in

each row, the sedimentation in the intake and delivery channel was decreased by 55%. However with applying

vanes in zigzag orientation the depth and shape of groove became more suitable and the sediment deposition

decreased by 75%.

M.M. Hossain, et al., [10], studied experimentally the scour around and downstream the bottom

vanes. They developed empirical formulae for predicating the maximum scour depth to serve the

determination of a safe depth for bottom vanes.

They used a 45.6 m long and 2.45 m wide straight flume. The model bed was sand of a median

diameter of 0.18 mm. Mobile-bed tests were executed for a constant discharge of 200 l/s. They tested vanes

that installed at four initial vane heights (0.06 m, 0.09 m, 0.12 m and 0.18 m) and five angles of attack (10°,

15°, 20°, 30° and 40°). For all experiments, the vane length was 0.40 m. At the location of the vane, the water

level was kept, 0.30 m above the initial bed level.

The formulae developed related the flow depth and the projected area of the vane. They did not

consider other parameters because the equilibrium live-bed scour did not vary with increasing the velocity or

the grain size. The resulting formulae were:

92.0

sin55.1

h

LHd

vv

s

…………………..……………...……………….................................. (3.1)

sin0768.0 vm Ld ………………………………………………..…………....................................... (3.2)

sin836.7 vS LA ………………………….…………………...……..………...................................... (3.3)

where;

ds : Maximum scour depths [L]

Hv : Vane height above the bed level [L]

Lv : Vane length [L]

: Vanes angle with respect the main flow direction [o]

h : Flow depth [L]

Where, the correlation coefficient was 0.82, 0.89, and 0.61 for three formulae, respectively.

The scour area and mean depth were found to be related to the projected vane length. It did not

increase appreciably with increasing the vane height.



4. LABORATORY EXPRIMRNTS

To study the efficiency of the bottom vanes and verify the data from the literature a laboratory

equipment has been designed and constructed at the HRI. Figure (4.1), shows the apparatus used in the

present study. The main flume is 60 cm wide, 60 cm deep and 20 m long. The lateral-intake channel is 20 cm

wide, 60 cm deep, and 3.0 m long and is fitted at a 90º to the main flume. The flume is constructed of bricks

sealed with smooth cement mortar. The flume consists of head and tail tanks and main, lateral and by-pass

channels. Two centrifugal pumps are used; the first is to supply water to the head tank from the ground sump,

and the other is submerged in the intake channel to deliver water to the bypass-channel. Water is controlled

using a control valve installed on the pipe connected to the feeding pump. The head tank has a weir, which is

calibrated to measure the flow that feed the flume, and a gravel box, which is used to provide an even flow

distribution across the flume. The flow enters the flume through an inlet screen to absorb any water eddies.

The model bed is made of smooth cement-sand mortar, overlaid on a 0.5-m layer of sand. To

represent the movable bed, a 5-m reach of the flume in front of the intake is filled with a 0.15 m deep layer of

a uniform PVC material with d50 = 2.5 mm, and a specific gravity of 1080 kg/m3. Precise point gauge is

installed to measure the bed level and the water depth. The gauge is mounted on carriage can move in the flow

and the perpendicular directions. Downstream water depth is controlled using a hinged gate. The intake

channel is located 8.0 m downstream the flume inlet. The fixed-floor elevation of the intake was levelled with

the movable bed in the flume. The intake channel has a sediment-collection trap followed by a screen to

collect the bed material; Photo (4.1) shows the flume during construction.



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13-

Tra

p f

or

sedim

ent

9-

Ste

el

scre

en1

5pla

n

11

- B

ed

mate

rial

10-

Soli

d f

loor

17

- T

ail

gate

18

- T

ail

tank

19

- D

rain

age p

ipe

16

- N

on

retu

rn v

alv

e1

2-

Inta

ke c

hannel

20-

By-p

ass

chann

el

Figure 4.1: Flume layout



Photo 4.1: Flume during construction

5. EXPERIMENTAL PROCEDURE

To study the influence of submerged vanes, flume flow was kept constant at 25 Lit/sec. The intake

discharge is varied to investigate four discharge ratios (Qr) with respect to the flow in the main channel (Qr =

0.10, 0.15, 0.20, and 0.30). For each discharge ratio three tail water depths are used. The tail water depth is

varied (Yt = 0.105, 0.12, and 0.135). Four vanes are installed in each row. The centreline of the row is

perpendicular to the main flow direction. The vanes are made of a steel plate of 2 mm thick and 12 cm long.

The row of vanes is fixed on a 2 mm thick steel plate. The distance between each two vanes is 10 cm, and the

distance between the vane and the flume wall is 7 cm, Photo (5.1) shows the submerged vanes.

Main Channel

Intake Channel

Inlet Tank



Photo 5.1: Submerged vanes

The experimental tests are divided into 4 sets; the sets are shown in figure (5.1), and photo (5.2).

Figure 5.1: Layout of the tests Program

THE FIRST SET: the experiments were carried out on a flat floor and no submerged vanes were used, this

set included 12 runs.

The second set: the experiments were carried out using a single row of vanes. Five positions of vanes were

tested, (bv/bd = 0.0, 0.5, 1.0, 1.5, and 2.0). After analyzing the measurements, the optimum position was

chosen to test 5 angles of vanes, ( = 10º, 20º, 30º, 40º, and 50º). The optimum orientation was chosen to test

4 heights of vanes with respect to tail water depth of the main channel, (Hv/Yt = 0.2, 0.3, 0.4, and 0.5). This

set included 168 runs.

12 No-Vanes 72 Triple Rows 168 Single Row 48 Double

Rows

Total Tests 300

60 Positions

60 Angles

48 Heights 60 Positions

36 Angles

36 Heights



Flat floor with no vanes

Single row of vanes

Triple rows of vanes

Double rows of vanes

Photo 5.2: The groups of the experimental tests

THE THIRD SET: the experiments were carried out for the case of triple rows of vanes. Three angles with

the flow direction were used ( = 20º, 30º, and 40º). After analyzing the measurements, the optimum

orientation was chosen to test three heights of vanes with respect to tail water depth, (Hv/Yt = 0.2, 0.3, and

0.4). This set included 72 runs.

THE FOURTH SET: the experiments were carried out for the case of double rows of vanes. Based on the

third set, the optimum relative height of vanes and the optimum angle was used to test four positions of vanes,

(bv/bd = 0.0, 0.5, 1.0, and 1.5). This set included 48 runs.

These different experimental arrangements are used to determine the best position, angle, and height of

vanes that lead to the minimum sediment that entered the intake channel

For each run, the backwater feeding is started first until its depth reaches higher than the required

downstream depth, Yt. Then the upstream feeding is started to adjust the tail water depth and the tail gate is

screwed gradually until the required depth is reached. After several trials, a two-hour period was selected as a

Flow

Flow

Flow

Flow

Intak

e

Intak

e

Intak

e

Intak

e



constant time for all runs. Flow velocity was measured using an electromagnetic current-meter. The velocity

measurements were carried out at three cross sections (Cs1, Cs2, and Cs3), figure (5.2).

After the running time, the run was stopped and the flume was drained and the volume of sediment

that entered the intake channel was measured, (the sediment displacement method), a squared beaker of (16.8

cm x 16.8 cm x 150 cm) was used to measure the volume of the sediment.

The expecting scouring area was recorded with a precision point gauge to monitor the bed topography

on a grid 20 cm x 10 cm. To estimate the maximum scour, a finer grid (5 cm x 10 cm) was sometimes used

depending on the shape of bed topography. Photo (5.3) and photo (5.4) are shown the used measuring devices

and the measurements.

V0.8Y

0.20m

4.0 m

1.0

m

Y

1.0 m

0.60 m

V0.6Y

V0.4Y

V0.2Y

Cs 1 Cs 2

Cs 3

Figure 5.2: Velocity measurements locations

Photo 5.3: The used measuring devices

Ultra-sonic flowmeter

Electro-magnetic currentmeter

Point gauge



Photo 5.4: The used measuring devices

A sample of the scour hole profiles and iso-scour lines is given to illustrate the scour holes in front of

the intake channel, appendix A. It is to be noted that, the zero coordinates, was taken at the intersection of the

center lines of the main and the intake channel. Also, a sample of the longitudinal sections along the center of

the main channel and along the right, and the left third of the channel width were given. Figure (A.1) shows

layout of the scale. It was concluded that, using vanes increases the scour depths in front of the intake channel,

but the position of scour changed from one run to another according to the submerged vane properties.

6. ANALYSIS OF EXPERIMENTAL RESULTS

The main aim of the present study is to estimate the influence of using the submerged vanes with the

proposed alignment, and to define the optimum parameters of vanes as sediment controller at water intakes.

Therefore, the following dimensionless parameters were used (SV/SVw, ds/dsw, bv/bd, α, Hv/Yt, vr/vl, Qr, and λ).

Figure 6.1: Submerged vanes at the intake

The relationships were divided into three sets, considered single, triple, and double rows of vanes in

front of intake channel. Consequently, graphs were constructed to illustrate the effect of the submerged vanes

on:

The sediment volume that entered the intake channel,

Scour hole depth in front of the intake channel, and

bv

bd

Qd

Main Channel

Intake

channel

Submerged Vanes

Up-stream Edge

Qm

Right wall Left wall

bm α

bv/bd =0



Velocity distribution in the intake channel.

6.1 Single Row of Vanes

Based on the experimental measurements, the effect of using a single row of vanes on the volume of

sediment entering the intake channel (SV), maximum scour depth in front of the intake (ds), and velocity

distribution in the intake channel (vr/vL), under different values of discharge ratios (Qr), and values of (λ-1), are

presented by means of graphs.

6.1.1. Case of Using Single Row of Vanes at Different Positions

Four vanes were used per row, and the angle of vanes with the direction of flow, α, was taken 25º, and

vanes height Hv, was considered 0.3 Yt, (tail water depth). These are based on the previous published material.

The effect of the relative positions of vanes in order to define the best position of the single row of vanes with

respect to the intake channel width, are illustrated, under the different values of discharge ratios and tail

Froude numbers.

Relationship between bv/bd, and SV/SVw

The effect of bv/bd, on SV/SVw, for using a single row of vanes, is given in figure (6.2), at different

values of discharge ratios, Qr, and values of λ-1. Form this figure, it is observed that;

The value of bv/bd = 0.5, gave the minimum SV/SVw, values. This means that, the best position of

the single row of vanes is at the upstream edge of intake channel.

For all the tested values of Qr, and bv/bd > 0.5 the value of SV/SVw, increases as bv/bd, increased,

while at bv/bd < 0.5, the value of SV/SVw, increases as bv/bd, decreased.

For most of the tested values of λ-1, and Qr = 0.15, the values of SV/SVw were less.

For most of the tested values of Qr, the value of bv/bd = 2.0, gave the higher SV/SVw, values.



Submerged Vane

Lvbv

Intake

bd

Hv

Qm

VanesLv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r

Figure 6.2: Relationship between bv/bd, and SV/SVw, for different Qr and λ-1 for single row of vanes

0.0

0.2

0.4

0.6

0.8

1.0

1.2

-0.50 0.00 0.50 1.00 1.50 2.00 2.50

bv /bd

SV

/ S

Vw

λ-1

= 6.54

0.0

0.2

0.4

0.6

0.8

1.0

1.2

-0.50 0.00 0.50 1.00 1.50 2.00 2.50

bv /bd

SV

/ S

Vw

λ-1

= 9.76



Submerged Vane

Lvbv

Intake

bd

Hv

Qm

VanesLv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r

Figure 6.2: Continue

Relationship between bv/bd, and ds/dsw

The effect of bv/bd, on ds/dsw, using a single row of vanes is given in figure (6.3), at different values of

discharge ratios, Qr, and values of λ-1. Form this figure, it is clear that;

For most of the tested values of λ-1, the values of ds/dsw, were more than one. This means that,

using of the submerged vanes led to increase the scour depth in front of the intake channel.

For all the tested values of Qr, and most of the tested values of λ-1, the value of ds/dsw, decreased

as the value of bv/bd, increased.

For most of the tested values of Qr, the value of bv/bd = 0.0, gave the higher ds/dsw, values, while at

the value of bv/bd =2.0, gave the lower ds/dsw, values.

For most of the tested values of λ-1, and all of the tested values of bv/bd, the value of ds/dsw,

increased as the value of Qr, decreased.

0.0

0.2

0.4

0.6

0.8

1.0

1.2

-0.50 0.00 0.50 1.00 1.50 2.00 2.50

bv /bd

SV

/ S

Vw

λ-1

= 13.90



Submerged Vane

Lvbv

Intake

bd

Hv

Qm

VanesLv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r

Figure 6.3: Relationship between bv/bd and ds/dsw for different Qr and λ-1 for single row of vanes

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

-0.50 0.00 0.50 1.00 1.50 2.00 2.50

bv /bd

ds /

dsw

λ-1

= 6.54

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

-0.50 0.00 0.50 1.00 1.50 2.00 2.50

bv /bd

ds /

dsw

λ-1

= 9.76



Submerged Vane

Lvbv

Intake

bd

Hv

Qm

VanesLv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r


6.1.2. Case of Using Single Row of Vanes at Different Angles

The value of bv/bd =0.5, gave the minimum SV/SVw, values, from the previous point, so that, the value

of bv/bd was taken 0.5. And vanes height, Hv, was considered 0.3 Yt, based on the pervious studies. Vane

angles are tested under the different values of discharge ratios and tail Froude numbers, in order to define the

optimum orientation of the single row of vanes.

Relationship between α, and SV/SVw

The effect of α, on SV/SVw, using a single row of vanes is given in figure (6.4), at different values of

discharge ratios, Qr, and values of λ-1. Form this figure, it is observed that;

The value of α = 35º- 40º, gave the lower SV/SVw, values. This means that, the optimum

orientation of the single row of vanes with the the direction of flow are 35º- 40º.

For most of the tested values of λ-1, and at Qr = 0.15, the values of SV/SVw, were less.

For all the tested values of Qr, and all values of α, the values of SV/SVw, increased as the values of

λ-1, increased.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

-0.50 0.00 0.50 1.00 1.50 2.00 2.50

bv /bd

ds /

dsw

λ-1

= 13.90



Submerged Vane

Lvbv

Intake

bd

Hv

Qm

VanesLv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r

Figure 6.4: Relationship between α and SV/SVw, for different Qr and λ-1 for single row of vanes

Submerged Vane

Lvbv

Intake

bd

Hv

Qm

VanesLv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 10 20 30 40 50 60

α

SV

/ S

Vw

λ-1

= 6.54

bv/bd = 0.5

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 10 20 30 40 50 60

α

SV

/ S

Vw

λ-1

= 9.76 bv/bd = 0.5




Relationship between α, and ds/dsw

The effect of α, on ds/dsw, using a single row of vanes is given in figure (6.5), at different values of

discharge ratios, Qr, and values of λ-1. Form this figure, it is observed that;

The values of ds/dsw, were more than one.

For all the tested values of Qr, and at all the tested values of λ-1, the value of ds/dsw, increased as

the value of α, increased.

For most the tested values of λ-1, and at all values of α, the value of ds/dsw, decreased as values of

Qr, increased.

For most of the tested values of Qr, the value of α =50º, gave the higher ds/dsw, values, while the

value of α =10º, gave the lower values.

For most of the tested values of Qr, the value of ds/dsw, increased as values of λ-1, increased.

For all the tested values of Qr, and at the lower values of λ-1, The value of α, had smaller effect on

the value of ds/dsw.

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 10 20 30 40 50 60

α

SV

/ S

Vw

λ-1

= 13.90 bv/bd = 0.5



Submerged Vane

Lvbv

Intake

bd

Hv

Qm

VanesLv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r

Figure 6.5: Relationship between α and ds/dsw for different Qr and λ-1 for single row of vanes

Submerged Vane

Lvbv

Intake

bd

Hv

Qm

VanesLv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 10 20 30 40 50 60

α

ds /

dsw

λ-1

= 6.54

bv/bd = 0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 10 20 30 40 50 60

α

ds /

dsw

λ-1

= 9.76

bv/bd = 0.5




Case of Using Single Row of Vanes at Different Heights

The value of bv/bd =0.5, and at the value of α= 35º - 40º, gave the minimum SV/SVw, values, these are

concluded from the previous analysis, so that, the value of bv/bd =0.5, and the value of α = 40º, were used.

Vanes heights are tested under the different values of discharge ratios and tail Froude numbers, in order to

define the best height of the single row of vanes.

Relationship between Hv/Yt, and SV/SVw

The effect of Hv/Yt, on SV/SVw, using a single row of vanes is given in figure (6.6), at different values

of discharge ratios, Qr, and values of λ-1. Form this figure, it is observed that;

Generally, values of SV/SVw, were lower than one.

For all the tested values of Qr, and all the tested values of λ-1, the value of Hv/Yt = 0.4, gave the

minimum SV/SVw, values. This means that, the best height of the single row of vanes is 0.4 Yt (tail

water depth).

For all the tested values of Hv/Yt, the value of SV/SVw, increased as the value of Qr, increased.

For the value of λ-1= 6.54, the value of Qr= 0.1, gave the minimum SV/SVw, values, while at λ-

1>6.54, the value of Qr= 0.15, gave the minimum SV/SVw, values.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 10 20 30 40 50 60

α

ds /

dsw

λ-1

= 13.90

bv/bd = 0.5



Submerged Vane

Lvbv

Intake

bd

Hv

Qm

VanesLv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r

Figure 6.6: Relationship between Hv/Yt, and SV/SVw, for different Qr and λ-1 for single row of vanes

Submerged Vane

Lvbv

Intake

bd

Hv

Qm

VanesLv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.1 0.2 0.3 0.4 0.5 0.6

HV/Yt

SV /

SV

w

λ-1

= 6.54

bv/bd = 0.5

α = 40°

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.1 0.2 0.3 0.4 0.5 0.6

HV/Yt

SV /

SV

w

λ-1

= 9.76

bv/bd = 0.5

α = 40°




Relationship between Hv/Yt , and ds/dsw

The effect of Hv/Yt, on ds/dsw, using a single row of vanes is given in figure (6.7), at different values

of discharge ratios, Qr, and values of λ-1. Form this figure, it is observed that;

The values of ds/dsw, were more than one. This means that, the using of the submerged vanes led

to increase the scour depth in front of intake channel.

For all the tested values of Qr, and most of the tested values of λ-1, the value of ds/dsw, increased as

the value of Hv/Yt, increased.

For the most values of Qr, the value of Hv/Yt = 0.5, gave the higher ds/dsw, values, while the value

of Hv/Yt = 0.2, gave the lower ds/dsw, values.

For all the tested values of λ-1, and all values of Qr, increasing the value of Qr, led to decease the

value ds/dsw.

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.1 0.2 0.3 0.4 0.5 0.6

HV/Yt

SV /

SV

w

λ-1

= 13.90

bv/bd = 0.5

α = 40°



Submerged Vane

Lvbv

Intake

bd

Hv

Qm

VanesLv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r

Figure 6.7: Relationship between Hv/Yt and ds/dsw for different Qr and λ-1 for single row of vanes

Submerged Vane

Lvbv

Intake

bd

Hv

Qm

VanesLv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0.1 0.2 0.3 0.4 0.5 0.6

Hv / Yt

ds

/ d

sw

λ-1

= 6.54

bv/bd = 0.5

α = 40°

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0.1 0.2 0.3 0.4 0.5 0.6

Hv / Yt

ds

/ d

sw

λ-1

= 9.76

bv/bd = 0.5

α = 40°




6.2 Triple Rows of Vanes

The effect of using the triple vane rows is illustrated. Under the used values of (Qr) and (λ-1), the

experimental results included vane angles (α), and vane height (Hv) are presented by means of graphs.

6.2.1 Case of Using Triple Rows of Vanes at Different Angles

Four vanes were used per row, and vanes height, Hv, is taken as 0.3 Yt, (tail water depth) based on the

pervious studies. The effect of the vane angles is studied to define the best orientation of the case of triple

rows of vanes in front of the intake channel under different values of discharge ratios and tail Froude numbers.

Relationship between α, and SV/SVw

The effect of α, on SV/SVw, using triple rows of vanes is given in figure (6.8), at different values of

discharge ratio, Qr, and values of λ-1. Form this figure, it is observed that;

For all the tested values of Qr, and values of λ-1, the value of α = 30º, gave the minimum SV/SVw,

values. This means that the optimum orientation of the case of triple rows vanes is 30º.

The effect of α, on the values of SV/SVw was more significant for the lower values of λ-1 than those

of the higher ones, where increasing the values of α, the values of SV/SVw, was increased.

For most of the tested values of λ-1, the value of Qr = 0.15, gave the smaller value of SV/SVw.

For all the tested values of α, and at the higher values of Qr, the value of SV/SVw, was increased, as

Qr, increased.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0.1 0.2 0.3 0.4 0.5 0.6

Hv / Yt

ds

/ d

sw

λ-1

= 13.90

bv/bd = 0.5

α = 40°



Submerged Vane

Lv

Intakebd

Qm Lv

Vanes

Hv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r

Figure 6.8: Relationship between α and SV/SVw, for different Qr and λ-1 for triple rows of vanes

0.0

0.2

0.4

0.6

0.8

10 20 30 40 50

α

SV

/ S

Vw

λ-1

= 6.54

0.0

0.2

0.4

0.6

0.8

10 20 30 40 50

α

SV

/ S

Vw

λ-1

= 9.76



Submerged Vane

Lv

Intakebd

Qm Lv

Vanes

Hv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r


Relationship between α, and ds/dsw

The effect of α, on ds/dsw, using triple rows of vanes at different values of discharge ratio, Qr, and

values of λ-1 is given in figure (6.9). Form this figure, it is observed that;

For the used flow conditions, most of the measured values of ds/dsw, are more than one.

For all the tested values of Qr, and most of the tested values of λ-1, the values of ds/dsw, increased

as the values of α, increased.

For all the tested values of λ-1, and α, the values of ds/dsw, decreased as the values of Qr, increased.

For all the tested values of Qr, and at λ-1, the value of α = 40º, gave the maximum ds/dsw values.

For all the tested values of Qr, the value of ds/dsw, increased as the value of λ-1, increased.

0.0

0.2

0.4

0.6

0.8

10 20 30 40 50

α

SV

/ S

Vw

λ-1

= 13.90



Submerged Vane

Lv

Intakebd

Qm Lv

Vanes

Hv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r

Figure 6.9: Relationship between α and ds/dsw, for different Qr and values of λ-1 for triple rows of vanes

1.0

1.5

2.0

2.5

3.0

3.5

4.0

10 20 30 40 50

α

ds /

dsw

λ-1

= 6.54

1.0

1.5

2.0

2.5

3.0

3.5

4.0

10 20 30 40 50

α

ds /

dsw

λ-1

= 9.76



Submerged Vane

Lv

Intakebd

Qm Lv

Vanes

Hv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r


6.2.2 Case of Using Triple Rows of Vanes at Different Heights

The value of α =30º, gave the minimum SV/SVw, values, under different flow conditions, and at the

vanes angle is 30º, the effect of relative vane heights, Hv/Yt, is illustrated to estimate the best one. The results

are presented by means of graphs.

Relationship between Hv/Yt, and SV/SVw

The effect of Hv/Yt, on SV/SVw, using triple vane rows at different values of discharge ratios, Qr, and


Generally, the values of SV/SVw, were lower than one.

For all the tested values of Qr, and λ-1, the value of Hv/Yt = 0.32, gave the minimum values of

SV/SVw. This means that, for the case of the triple vane rows, the sediment that entered the intake

channel were the minimum, at the height of vanes is 0.32 of the tail water depth,

For λ-1 >6.54, the value of Qr =0.15, gave the minimum SV/SVw values, while for λ-1 =6.54, the

value of Qr =0.10, gave the minimum SV/SVw values.

For most of the tested values of Qr, and at all values of Hv/Yt, the values of SV/SVw, increased as

the value of λ-1, increased.

1.0

1.5

2.0

2.5

3.0

3.5

4.0

10 20 30 40 50

α

ds

/ d

sw

λ-1

= 13.90



Submerged Vane

Lv

Intakebd

Qm Lv

Vanes

Hv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r

Figure 6.10: Relationship between Hv/Yt and SV/SVw, for different Qr and λ-1 for triple rows of vanes

Submerged Vane

Lv

Intakebd

Qm Lv

Vanes

Hv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r

0.0

0.2

0.4

0.6

0.8

1.0

0.1 0.2 0.3 0.4 0.5

HV/Yt

SV /

SV

w

λ-1

= 6.54

α = 30°

0.0

0.2

0.4

0.6

0.8

1.0

0.1 0.2 0.3 0.4 0.5

HV/Yt

SV /

SV

w

λ-1

= 9.76

α = 30°




Relationship between Hv/Yt, and ds/dsw

The effect of Hv/Yt, on ds/dsw, using triple rows of vanes for different values of discharge ratios, Qr,

and values of λ-1 is given in figure (6.11). Form this figure, it is observed that;

For the tested values of λ-1, and Hv/Yt, the values of ds/dsw, decreased as the values of Qr,

increased.

The values of ds/dsw, were more than one. This means that using triple rows vanes at the different

heights led to increase the scour depth in front of intake channel.

For all the tested values of Qr, and at all values of λ-1, the values of ds/dsw, increased as the values

of Hv/Yt, increased.

For all the tested values of Qr, the values of ds/dsw, increased as the values of λ-1, increased.

Submerged Vane

Lv

Intakebd

Qm Lv

Vanes

Hv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r

Figure 6.11: Relationship between Hv/Yt and ds/dsw, for different Qr and λ-1 for triple rows of vanes

0.0

0.2

0.4

0.6

0.8

1.0

0.1 0.2 0.3 0.4 0.5

HV/Yt

SV /

SV

w

λ-1

= 13.90

α = 30°

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0.1 0.2 0.3 0.4 0.5

HV/Yt

ds

/ d

sw

λ-1

= 6.54

α = 30°



Submerged Vane

Lv

Intakebd

Qm Lv

Vanes

Hv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r


1.0

1.5

2.0

2.5

3.0

3.5

4.0

0.1 0.2 0.3 0.4 0.5

HV/Yt

ds

/ d

sw

λ-1

= 9.76

α = 30°

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0.1 0.2 0.3 0.4 0.5

HV/Yt

ds

/ d

sw

λ-1

= 13.90

α = 30°



6.3 Double Rows of Vanes

The effect of using the double vane rows is illustrated. Under the used values of (Qr) and (λ-1), the

experimental results included double vane rows positions (bv) are presented by means of graphs.

6.3.1 Case of Using Double Vane Rows at Different Positions

Four vanes were used per row, the angle of vanes with main flow direction, α, is taken as 30º, and the

vanes height, Hv, is taken as 0.3 Yt, (tail water depth), these are based on the analysis of the case of the triple

vane rows. Under different flow conditions, the effect of relative vane positions, bv/bd, is illustrated to estimate

the best one.

Relationship between bv/bd, and SV/SVw

The effect of bv/bd, on SV/SVw, using double vane rows for different values of discharge ratios, Qr, and


The value of bv/bd = 0.75, gave the minimum SV/SVw, values. This means that, at bv/bd = 0.75, the

sediment volume that entered the intake channel were the minimum.

For most of the tested values of λ-1, the values of SV/SVw, increased as the values of Qr, increased.

For all the tested values of Qr, and λ-1, the value of bv/bd =0.0, gave the maximum SV/SVw, values.

For most of the tested values of Qr, the values of SV/SVw, decreased as the value of λ-1, decreased,

For λ-1 >6.54, the value of Qr =0.15, gave the minimum SV/SVw values, while for λ-1 =6.54, the

value of Qr =0.10, gave the minimum SV/SVw values.

The effect of the bv/bd, on the value SV/SVw, was more significant for the lower values of λ-1, than

those of the higher ones.

Hv

Submerged Vane

Lvbv

Intakebd

Qm

VanesLv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r

0.0

0.2

0.4

0.6

0.8

1.0

-0.5 0.0 0.5 1.0 1.5 2.0

bv /bd

SV /

SV

w

λ-1

= 6.54



Figure 6.12: Relationship between bv/bd, and SV/SVw, for different Qr and λ-1 for double vane rows

Hv

Submerged Vane

Lvbv

Intakebd

Qm

VanesLv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r


Relationship between bv/bd, and ds/dsw

The effect of bv/bd, on ds/dsw, using double vane rows for different values of discharge ratios, Qr, and


For most of the tested values of λ-1, and at all values of bv/bd, the values of ds/dsw, were more than

one. This means that, the using of submerged vanes led to increase the scour depth in front of

intake channel.

0.0

0.2

0.4

0.6

0.8

1.0

-0.5 0.0 0.5 1.0 1.5 2.0

bv /bd

SV /

SV

w

λ-1

= 9.76

0.0

0.2

0.4

0.6

0.8

1.0

-0.5 0.0 0.5 1.0 1.5 2.0

bv /bd

SV

/ S

Vw

λ-1

= 13.90



For the tested values of Qr, and λ-1, the value of ds/dsw, decreased as the value of bv/bd, increased,

except for bv/bd = 0.5 to1.0.

For most values of λ-1, and at all the tested values of bv/bd, the value of ds/dsw, decreased as Qr,

increased.

For all the tested values of Qr, and at all values of λ-1, the value of bv/bd =1.5, gave the lower

ds/dsw, values.

Hv

Submerged Vane

Lvbv

Intakebd

Qm

VanesLv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r

Figure 6.13: Relationship between bv/bd and ds/dsw for different Qr and λ-1 for double vane rows

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

-0.5 0.0 0.5 1.0 1.5 2.0

bv /bd

ds

/ d

sw

λ-1

= 6.54

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

-0.5 0.0 0.5 1.0 1.5 2.0

bv /bd

ds /

dsw

λ-1

= 9.76



Hv

Submerged Vane

Lvbv

Intakebd

Qm

VanesLv

bm

Q = 0.30

Q = 0.15

Q = 0.20r

Q = 0.10r

r

r


6.4 Comparison Between The Considered Cases

The comparison between the different considered cases, the single, double, and the triple vane rows,

are illustrated in order to define the effect of the number of vane rows on the volume of sediment that entered

the intake channel, SV, maximum scour depth in front of the intake, ds, and velocity distribution in the intake

channel, vr/vL, this comparison is presented by means of graphs.

Relationship between Qr, and ds/dsw

At optimum vane angles, heights, and positions for the cases of the single, double, and triple vane

rows. Figure (6.14) gave the effect of Qr, on ds/dsw, for different values of λ-1. Form this figure, it is observed

that;

For all the tested values of λ-1, and at different cases of vane rows, the values of ds/dsw, increased

as the values of Qr, decreased.

The case of triple vane rows gave the higher scour depth values in front of intake channel, while

the case of the single row of vanes gave the lower values.

For the tested values of Qr, and at different cases of vane rows, the value of ds/dsw, increased as

values of λ-1

, increased.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

-0.5 0.0 0.5 1.0 1.5 2.0

bv /bd

ds

/ d

sw

λ-1

= 13.90



Single Row Triple RowsDouble Rows

Figure 6.14: Relationship between Qr , and ds/dsw, for different cases of vane rows and λ-1

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0.05 0.10 0.15 0.20 0.25 0.30 0.35

Qr

ds /

dsw

λ-1

= 6.54

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0.05 0.10 0.15 0.20 0.25 0.30 0.35

Qr

ds /

dsw

λ-1

= 9.76

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0.05 0.10 0.15 0.20 0.25 0.30 0.35

Qr

ds /

dsw

λ-1

= 13.90



Relationship between Qr, and SV/SVw

At optimum vane angles, heights, and positions for the cases of the single, double, and triple vane rows.

Figure (6.15) gave the effect of Qr, on SV/SVw, for different values of λ-1. Form this figure, it is observed that;

For the tested values of λ-1, and at different cases of vane rows, the value of SV/SVw, increased as

the value of Qr, increased.

For the considered conditions, the triple vane rows gave the maximum % Reduction of the

volume of sediment that entered the intake channel; the minimum % Reduction is occurred at the

case of the single row of vanes.

The difference in % Reduction of the volume of sediment that entered the intake channel between

double and triple vane rows of vanes is small.

Single Row Double Rows Triple Rows

Figure 6.15: Relationship between Qr, and Sv/SVw, for different cases of vanes and λ-1

Single Row Double Rows Triple Rows

0.0

0.2

0.4

0.6

0.8

1.0

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35

Qr

SV/S

Vw

λ-1

= 6.54

0.0

0.2

0.4

0.6

0.8

1.0

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35

Qr

SV/S

Vw

λ-1

= 9.76




Relationship between Qr, and vr/vL

At optimum vane angles, heights, and positions for the cases of the single, double, and triple vane rows.

Figure (6.17) gave the effect of Qr, on vr/vL, for the value of λ-1 = 6.54, Form this Figure, it was observed that;

Generally, using of vanes decreased values of vr/vL. This means that using of vanes led to non-

uniform distribute of the velocity in the intake channel.

The values of vr/vL, had the higher values for the case of flat floor (no vanes), while had the

minimum values for case of double rows of vanes.

For the tested cases, the value of vr/vL, increased as values of Qr, increased. This means that

maximum separation zone is occurred at the lower value of Qr.

Figure 6.17: Relationship between Qr, and vr/vL, for different cases of vanes and at λ-1 = 6.54

0.0

0.2

0.4

0.6

0.8

1.0

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35

Qr

SV/S

Vw

λ-1

= 13.90

0.0

0.2

0.4

0.6

0.8

1.0

0.05 0.10 0.15 0.20 0.25 0.30 0.35

Qr

Vr/

VL

No Vanes Single Row Triple Rows Double Rows



7. CONCLUSIONS AND RECOMMENDATIONS

The present experimental study was conducted to investigate the possibility of minimizing the

sedimentation problems in a diverted channel intake, by using submerged vanes in front of intake channel.

The following conclusions were drawn:

a. Using a single row of vanes

The best tested position of single row of vanes was at a half way of the intake channel width; this is

because the volume of the sediment that entered the intake channel was less compared with other

tested cases.

For all considered values of the relative discharge, and Froude criteria, the value of relative scour

depth, decreased as the value of relative position, increased.

From the sediment point of view, the optimum angle which minimizes the diverted sediment is 35º -

40º, with the main flow direction.

Scour in front of the intake channel increased as the angle of vanes with the main flow direction

increased.

For minimizing the sediment transport that entered the intake, the optimum height of vanes was 0.4,

of the tail water depth, while the vane height should be adjusted with respect to the navigation

constraints.

Scour in front of the intake channel increased as the height of vane increased.

The single row of vanes that were tested under the used conditions reduced the sediment by 40% to 75

%.

b. Using double vane rows

The best position of double rows of vanes was a position that lies at 0.75 times of the intake channel

width from the upstream edge of the intake. This is because the volume of the sediment that entered

the intake channel was smaller if compared with other tested cases.

The value of relative scour depth decreased as the value of a relative position increased. The values of

relative depth of scour, had the least value at a position lies at 2.0 times of the intake width, and had

the highest value at a position that lies at the centreline of the intake channel.

The tested double rows of vanes reduced the sediment by 50% to 85 %.

c. Using triple vane rows

The optimum angle of the triple vane rows is 30º, with main flow direction.

For minimizing the sediment transport that entered the intake, the optimum height of vanes should be

0.32 of the tail water depth, the vane height should be adjusted with respect to the navigation

constraints.

Scour in front of the intake channel increased as the angle and/or height of vanes increased.

The tested triple rows of vanes that reduced the sediment by 55% to 90%.

Final conclusions.

Generally, the submerged vanes technique at water intakes had a good influence on preventing the

sediment to be diverted into the intake channel. The proposed alignment effectively minimized the volume of

sediment that entered the intake channel in case of release a relative discharge higher than 0.2.

- Using the submerged vanes increased the scour depths in front of intake channel, so that the stability

of the riverbed, intake foundations level, and the navigational constraints should be checked.



- Using the submerged vanes increased the separation zone length in the intake channel. This means that

the vanes led to a non-uniform distribution of flow in the intake channel. Maximum separation zone occurred

in the case of triple rows of vanes.

- Although submerged vanes minimized the sediment to be diverted to the intake channel, but it

generated undesirable changes in the sediment distribution downstream the intake channel.

7.1 Recommendations

There are some considerations, which could be recommended for future studies. These are to:-

Test a wider range of the considered conditions.

Study the effect of different channel bed widths, and bed materials.

Investigate the effect of the different dimensions and angles of the intake channel.

Test modified shapes of the vanes.

Study the effect of vane length, and lateral spacing of the vanes.

Study the effect of using sill and skimming wall at the entrance of the intake.

Investigate the effect of different shapes of the upstream edge of the diverted channel.

Study the scour problems due to the use of submerged vanes with the tested specifications.

8. BIBLIOGRAPHY

1. Abdelazim, M. A., (2004). "River Morphological Model Studies at EL-Kurimat Power Station",

Hydraulics Research Institute, NWRC, Egypt. Report No.106/2004

2. Amin, A. M., (2005). "Study of Sedimentation at River Side Intakes", Ph.D. Thesis, Dept. of Civil

Engineering, El-Minufiya University, Egypt.

3. Amin, A. M., and Fahmy, S. Abd El-Haleem., (2007). "Hydrographic Survey at EL-Kurimat Power

Station", Hydraulics Research Institute, NWRC, Egypt. Report Progress (5) No.82/2007.

4. Arved J. Raudkivi (1993). "Exclusion and removal of sediment from diverted water", Hand Book, IAHR

Hydraulic structures design manual No. 6.

5. Ashok S. and K., Keshava (1997). "A Numerical Study of Division of Flow in Open Channels", Journal

of the Hydraulics Division, ASCE, Volume 34 No. 5.

6. Delft Hydraulics and, HRI (1995). "Physical Model Study tests with Bottom Vanes for Fairway

Improvement of the Bovenwall", Hydraulics Research Institute, NWRC, MWRI, Egypt. and Delft Hydraulics,

the Netherlands. Report, January, 1995.

7. Fahmy S. F. AbdelHaleem, (2008). "Sediment Control at Riverside Intakes", M.Sc. Thesis, Dept. of

Civil Engineering, El-Minufiya University, Egypt.



8. Helal, Esam E. Y., (2006). "Improving the Flow Characteristics at Open Channel's Junctions", Ph.D.

Thesis, Dept. of Civil Engineering, El-Minufiya University, Egypt.

9. Helmut, S., and Felix Mtalo, (1991). "Sediment Control at River Intakes", African Journal of science

and technology, series A Technology, Oct.

10. M.M. Hossain, MD. Rashedul Islam, Suman S., and F. Sara, (2004). "Laboratory Tests on Scour

around Bottom Vanes", Report, at BUET, Delft University of technology, Delft, the Netherlands.

11. Odgaard, A.J., (2005). "Iowa Vanes An Inexpensive Sediment Management Strategy", IIHR-

Hydroscience and Engineering, College of Engineering, the University of Iowa.

12. Odgaard, A.J. and Hong-Yuan E. Lee (1984). "Submerged Vanes for Flow Control and Bank

Protection in Streams", Iowa Institute of Hydraulics Research, Iowa City, Report for Project HR-255.

13. Odgaard, A.J., and Wang Y. (1991a). "Sediment Management with Submerged Vanes1: Theory",

Journal of the Hydraulics Division, ASCE, Vol. 117(3), 267-283.

14. Odgaard, A.J., and Wang Y. (1991b). "Sediment Management with Submerged Vanes2: Application",

Journal of the Hydraulics Division, ASCE, Vol. 117(3), 284-302.

15. Rashwan, I. and Tarek, A. (2004). "Dividing Flow at 90oOpen Channel Junction" Mansoura University,

Vol. 29 No. 1

16. Sadjedi Sabegh M., Habibi M., and Rahmanian M. (2004). "An Experimental Investigation on

Sediment Control in Intakes Using Submerged Vanes", Soil Conservation Watershed Management Research

Center, P.O. Box 13445-1136.Tehran, Iran.

17. Wang Y., and Odgaard, A.J., (1993). "Flow Control with Vorticity ", Journal of the Hydraulics

Division, ASCE, Vol. 31, No. 4.

18. Wang Y., Odgaard A.J., Melville, W., and Jain, S. C. (1996). "Sediment Control at Water Intakes",

Journal of the Hydraulics Division, ASCE, vol. 122(6), 353-3



List of Research Group Members

Name Country Organization e-mail

Dr. Abdel Azim Mohamed Ali Egypt Hydraulics Research Institute [email protected]

Dr. Yonas michael Ethiopia Addis Ababa University [email protected]

Eng. Fahmy Salah Abdelhaleem Egypt Hydraulics Research Institute [email protected]

Scientific Advisor:

Prof. Petru Boeriu

Associate Professor of River Engineering

UNESCO-IHE, the Netherlands

Full Profiles of Research Group Members are available on: The Nile Basin Knowledge Map

http://www.NileBasin-Knowledgemap.com



http://www.nilebasin-knowledgemap.com/

APPENDIX (A)

Sample of Experimental Results


Nile Basin Capacity Building Network ( NBCBN ) A-1

Main channel

Qm

0

Intake

bd

Y

X bm

Figure A.1: Layout of the scale



Photo A.1: Scour hole without submerged vanes, (Qr = 0.30, λ-1 = 6.54)

FigureA.2 : Iso-scour lines and scour hole profile without submerged vanes, (Qr =0.30, λ-1= 6.54)

Run 10

Left third

Right third

Center

Flow



Photo A.2: Scour hole with single row of vanes, (bv/bd =0.50 , α = 40º , Hv/Yt =0.4), (Qr =0.30, λ-1= 6.54)

Figure A.3: Iso-scour lines and scour hole profile with single row of vanes, (bv / bd = 0.50 , α = 40º , Hv/Yt

=0.4), (Qr =0.30, λ-1= 6.54 )

Run 166

Flow



Photo A.3: Scour hole with triple rows of vanes, (α = 30º, Hv/Yt =0.3), (Qr =0.30, λ-1= 6.54)

Figure A.4: Iso-scour lines and scour hole profile with triple rows of vanes, (α = 30º, Hv/Yt =0.3), (Qr =0.30,

λ-1= 6.54)

Run 238

Flow



Photo A.4: Scour hole with double rows of vanes, (bv/bd =1.0 , α = 30º , Hv/Yt =0.3), (Qr =0.30, λ-1= 6.54 )

Figure A.5: Iso-scour lines and scour hole profile with double rows of vanes, (bv/bd =1.0 , α = 30º , Hv/Yt

=0.3), (Qr =0.30, λ-1= 6.54 )

Run 286

Flow

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