canal outlets

7/21/2019 Canal Outlets

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Canal Outlets


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Introduction

An outlet is a small structure which admits water from the

distributing channel to a water course or field channel.

An outlet is a sort of head regulator for the field channel

delivering water to the irrigation fields.

The responsibility of maintenance of the distributing channel

and the whole canal network lies with Government, while

that of the field channel lies with the farmer. The outlet is the

connecting medium for the two.


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A canal outlet should fulfil the following requirements

1. The outlet should be strong, with no moving parts liable to bedamaged or requiring periodic attention and maintenance.

2. It should be so designed that the farmer cannot temper with its

functioning and any interference from him should be easilydetectable.

3. Since a large number of outlets are fied on a distributing

channel, the most essential requirement is that it should be cheap.


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!. The design should be simple so that it can be constructed orfabricated by local masons or technicians.

". It should be possible for the outlet to wor# efficiently with a

small wor#ing head.

$. The outlet should draw its fair share of silt carried by the

distributing channel.

%. &rom the farmer's point of view, the outlet should give a fairly

constant discharge. (owever, from the canal regulation point of

view, the outlet should draw proportionately more or less

discharge with the varying supply in the distribution channel.

A canal outlet should fulfil the following requirements


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Types of Outlets

)utlets may be classified under the following three

heads *

1. +onmodular )utlet.

2. Semimodule or &leible -odule.

3. igid -odule.


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on!modular Outlet

/ nonmodular outlet is the one in which the discharge dependsupon the difference in level between the water levels in the

distributing channel and the water course.

The discharge through such an outlet varies in wide limits withthe fluctuations of the water levels in the distributing and the field

channels.

The common eamples under this category are * submerged pipeoutlet, masonry sluice and orifices, and wooden shoots.


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The pipe, varies from 10 to 30 cm in diameter, and are frequently

laid on a light concrete foundation to prevent uneven settlement

and consequent lea#age.

They are generally fied horiontally at right angles to the flow

direction


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"emi!module or #le$ible Outlet

A fle$ible outlet or semi!module is the one in which the discharge is

affected by the fluctuations in the water level of the distributing

channel while the fluctuations in the water levels of the field

channel do not have any effect on its discharge.

The various outlets in common use that fall under this category arepipe

outlet, ennedys gauge outlet, 4rumps open flume outlet and pipecum open flume outlet.

Common types of flexible outlets-

Pipe Semi Module

%ennedy&s gauge outlet Open Flume Outlet (OFMs) -

Crumps Adjustable proportionate Module(Crumps APM)

Adjustable Orifce Semi module (AOSM)


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'ipe Outlets (ischarging #reely in the Atmosphere

The discharge through such an outlet will depend only upon the

water level of the distributary, and will be independent of thewater level of the water!course so long as the pipe is discharging

freely.

Silt conduction for such an outlet is quite good 5 efficiency is high.

6ut a freely falling 7et outlet can be provided only at a few placeswhere sufficient level difference between the distributary and water

course is available.

The discharge can be easily computed by using the equation


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%ennedy&s gauge outlet8 It is made of cast iron and consist of three main parts

1. /n orifice with bellmouth entry

2. /long epanding delivery pipe3. /n intervening vertical air column above the throat

. The discharge through this semimodule is given by


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The suitabilit o! the tpe o! the semi module

outlet is determined based on the ratio o! parentcanal dischar"e (#) to the dischar"e o! the outlet ($) and the throat %idth (&t) as detailed

belo%'

i) !or (#$ ) or * +, and &t . cm Open

Flume Module( OFM)

ii) !or (#$ ) or * +, and &t . cmAdjustable Proportional module ( APM )

!or (#$ ) / +,

1! the abo2e re$uirements do not suit the site

Open #lume Outlets


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The abo2e conditions are !urther e6plained as belo%

Arri2e at the ratio o! parent channel out let channel'

1! it is or * +,3 select OFM' Calculate the &t ( throat

%idth )3 usin" %eir !ormula'1! &t is / . cm it is o7'

Other%ise select A'P'M'

8or7 out the &t usin" the sluice !ormula settin" thecrest o! outlet at less than ,'9, : !rom FS; o! Parent

Channel and adjustin" the hei"ht o! outlet openin"'1! &t * or / . it is o7

Other%ise "o !or pipe semi module (PSM)3 i! it ispossible to do so'

Chec7 !or proportionall

Open #lume Outlets


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Open #lume Outlets

It is a weir type outlet with a constricted throat and an e$panding

flume on the downstream. (ue to the constriction a super!criticalvelocity is ensured in the throat and thereby allowing the

formation of a )ump in the e$panding flume.

The formation of hydraulic )ump makes the outlet discharge

independent of the water level in the water!course* thus makingit a semi!module.

There are two types of open flume outlets*

+. 'an)ab open flumes outlet

. Crump&s Ad)ustable open flume outlet


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A smooth %eir %ith a throat constricted su o! depth o! %aterabo2e the crest o! out let'

Formation o! hdraulic jump ma7es the out letindependent o! %ater le2el in the out let channel

Open FlumeModule(OFM)


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# in Cumecs * ? &t@+

Where K = a constant depending upon the width of theume Bt= throat width of the weir (minimum 6 cm)

For Bt , 6 cm to cm K=!"6 cm to !# cm K= !"6$

% !#cm K= !"66& = head o'er crest in m"

1t is most suited to tail cluster and proportionatedistribution'

;en"th o! throat (crest) * +@

Settin" @ * ,'B :3 %here : is FS dept o! Parent canal Minimum modular %or7in" head * ,'+ @ Crest le2el * S FS; D ,'B : S approach to throat ----- one cur2ed and di2er"in"

and another strai"ht

:S e6pansion------- splaed to 4 in 4, to meet thebed %idth o! the out let channel

Open Flume Module


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Open Flume Module


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O* F+M Module-


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'an)ab Open #lumes Outlet

In 9un7ab open flume outlet, the upstream approach is made

curved and the downstream approach is made straight.

The length of the throat is #ept 2(. The width of the flume at

the downstream end is #ept 0.3 m wider than the throat width

:;0 to ?0@. The minimum modular loss

involved in such an outlet is about 0.2(.


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Crump&s Ad)ustable Open #lume Outlet

In 4rump's outlet the upstream face is set bac# by a distance

AB' equal to the width of the opening of the module.

It enables the outlet to ta#e a fare share of silt. The throat is

constricted to ensure hypercritical velocity. The length of the

throat is #ept equal to 2."(.

The discharge is given by

where * C throat width:m< 4 C4oefficient of discharge C1.%1

q C discharge through outlet

( C head over the crest:m? >1.$$2

10&S m >2.31? >1.?%2


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.esign of OFM


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Canal Out lets

Open Flume Module (OFM)9

@draulic :esi"nN

atio of ?> = C"E C"CD

= !!"/ED L #C

&ence O"F"M" is roposed"

F7. in the parent channel, . = C"/EC m

:epth o! =o% in the parent channel at +rddischar"eN

:n*,'5BEm (assumed)

For #Erd

.ischarge in arent 2anal ?n= #E J ? = C"6#6 cumecs+et .n= C"$ m , 4rea = !"#$# m

#

erimeter = E"E$# m, = C"E/#, and #E= C"!/

elocit: = C"C$ msec

.ischarge = C"6#6 cumecs

&ence .n i"e", depth of ow of C"$ m in the parent channel assumed

Canal Out lets & Modular


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Outlets Open Flume Module (OFM)N

The dischar"e o! the outlet $ (in cumecs) is "i2en b the !ormulaN

$ * ? 6 &t6 @+

8here ? * Constant dependin" upon the %idth o! =ume

&t* Throat %idth o! %eir

@ * @ead o2er crest in meters

@n * @ead o2er crest at + # * ( @ D 6 )

For !ull dischar"e $ * ? 6 &t6 @+ - ( 4 )

For + dischar"e $ * ? 6 &t6 (@n)+* ? 6 &t6 (@-6)

+ - ( + )

& di2idin" e$uation (4) b e$uation (+)

$ + $ * ? 6 &t6 @+ + ($) ? 6 &t6 (@ - 6)

+

+ * (@+(@ - 6)+)+

(+)+* (@+(@ - 6)+)+

4'4, * @ (@ - 6)

,'4 ' @ * 4'4 ' 6

@ * E'++5 6

6 * ,'4. m



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Outlets Open Flume Module (OFM)9Minimum Head required (modular) = 0.2 x H = 0.2 x 0.575 = 0.115 m

Available Working Head = Dieren!e o "#$%& in 'aren anal and * + ,ake anal= -2.1/ + -1./72 = 0.7 m *

q = x x H32

4alue o a& 6er #8 121+1/-- = 1.9

= q 3 ( . H32)

= 0.0-0 3 1.9 x (0.575)32= 0.112 m

q = x

x H32

=1.9 x 0.112 x 0.57532

=0.0-0 !ume!& *

"or 23rdq8

qn=(23 x 0.0-0) = 0.05 !ume!&

Hn=H + x =0.575 + 0.19 =0./ m

= x x Hn32

=1.9 x 0.112 x 0./32= 0.05 !ume!& *n order o mainain :e modulari; o :e oule< :e olloing 6arameer& are

ado6ed.

= 0.112 m

H = 0.575 m

,:roa $eng: = 1.150 m

re& $evel = -1.7 m


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.esign of OFM


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Open Flume Module


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O* F+M Module-


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&G&.4+;2 .7;* OF 4M


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2anal outlets P Modules

Adjustable Orifce Semi Module (A'O'S'M) orAdjustable Proportional Module (APM)

:ischar"e throu"h outlet in cumecs

# * E', &t @s4+

G =&eight of opening in meters"Bt =-hroat width (minimum C"C6 m )

& =.epth of water in parent canal o'er the crest in meters

&s= .epth to under side of the roof 0loc< 0elow F7+ of parent canal"

&s= & H G , &sI C"DC .

: % (#E ) &7etting of crest, & = C"/C J . , where . = Full suppl: depth in the parentcanal

7etting of crest shall not 0e 0elow .7 B"+"


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2anal outlets P Modules

7etting of crest shall not 0e 0elow .7 B"+"Minimum modular head &m = C"/ &s for modularit: 0etween fullsuppl: and an: fraction of full suppl:"

2rest le'el Q 7 F7+8 C"/ .

+ength of throat = width of roof 0loc< A &

7 slope of glacis = cur'e with radius #&"s approach wings =one cur'ed and the other straight, top at F7+ AC"! m

.7 eJpansion =! in !C to meet 0ed width of outlet channel


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.esign of 4M

@draulic ParticularsN

S'o' :etails ?uppam Major :P 4G-J ?uppam major :P 4G-J

At FS :ischar"e Condition At + FS :ischar"e Condition

4' :ischar"e in Cumecs ,'.. ,',49 ,'E+E ,',4+

+' &ed %idth in m 4'4,, ,',, 4'4,, ,',,

' FS: in m,'.4, ,'45, ,'EB5 ,'4+,E' &ed !all 4 in +5,, +,,, +5,, +,,,

5' alue o! n ,',+, ,',+, ,',+, ,',+,

.' elocit in ms ,'549 ,'+4 ,'E.E ,'49

G' Side slopes 4'5 N 4 4'5 N 4 4'5 N 4 4'5 N 4

9' Free board in m ,'.4, ,'E5, ,'.4, ,'E5,

B' C&; m 9,'+.B 9,'E++ 9,'+.B 9,'E++

4,'FS; m 9,'9GB 9,'5G+ 9,'G.E 9,'5E+

44'T&; m 94'E9B 94',++

4+'L; m 94'E9B 94'E9B

Propose APM i! # $ +,3 or # $ / +,3 and &t ., mm

Jatio o! # $ * ,'.. ,',49 * 5' / +,

@ence APM is proposed'


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.esign of 4M


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.esign of 4M

&:draulic .esign of 4M

ropose 4M if ?> L #C and Bt L 6 or ?> %#C

atio of ?> = C"6E6 C"C!D = E"EEE % #C @ence A P M isproposed

$*E', 6 &t6 6 @s4+

Where G = &eight of opening in meters

Bt = -hroat width

& =.epth of water in parent canal o'er the crest in meters"

&s= .epth of under side of the roof 0loc< 0elow F7+ of parent

canal

For + !ull suppl arent canal ON ta"m C"CD s>" m

perimeter = #"DD/ m C"/EE m

= C"E!6 m C"C/ m

i f


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.esign of 4M

:ischar"e throu"h the outlet in cumecs'

$ * E', 6 &t6 6 ( @s ) Q(Pa"e 443 Clause .''4 o! 1S N GB9.-4BG.)

Throat %idth &t * $ (E', 6 (@s)Q6)

;et &t * ,',. m

$ * E', 6 &t 6 6 @s4+ --------------e$uation (4)

+ ($) * * E', 6&t 6 6 (@sn)4+ --------------e$uation (+)

8here @sn* @s- (: - :n) * E', 6 &t 6 6 (@s - (,'.4, - ,'EB5))4+

* E', 6 &t 6 6 (@s - ,'445)4+

:i2idin" e$uation (4) b (+)

$ * + ($) * E', 6 &t 6 6 @s4+ E', 6 &t 6 6 (@s - ,'445)Q

+ * @s4+ (@s- ,'445)4+

* + 6 @s4+* 6 (@s- ,'445)4+

E 6 @s* B6 (@s- ,'445)5 @s* 4',+

@s* ,'+,G m and @s4+* ,'E55

@sn * @s D ( : D :n ) * ,'+,G D ( ,'.4, D ,'EB5 ) * ,',B+m


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.esign of 4M

* $ $',6&t6(@s)4+

= C"C!D E', 6 C"C6 J ,'E55

*,'4.Em sa ,'4.5 m

# * E', &t ( @s ) Q *E', 6 ,',. 6 ,'4.5 6,'E55 * ,',49 cumecs

>n = $"CE Bt G ( &sn ) S *E', 6 ,',. 6 ,'4.5 6,', * ,',4+ cumecs

-he following arameters ma: 0e adopted

Bt = C"C6C m

2rest +e'el = 7 F7+ 8 & = A DC"C/

& = C"E/# m

G = C"!6 m

&s = C"#C/ m

W= 7etting forward of the .7 wing wall of the approach=C"!

-he setting of the Wing wall W = K >? (Bu A .#)


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.esign of 4M

CRUMPS ADJUSTABLE PROPORTIONAL MODULE


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CRUMP S ADJUSTABLE PROPORTIONAL MODULE

O* F+M O-+- W;-& OOF B+O2K


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O* F+M O-+- W;-& OOF B+O2K


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2anal Outlets P Modules

Pipe semi module (PSM)

:esi"n criteria

-he discharge through pipe semi module is gi'en 0:

? = 2d " 4 (#g hc)!#

Where 2d = C"6# for free pipe out let

hc = head on 7 a0o'e the centre of pipe

hcshould 0e more than !" times the dia of the pipe proposed"

-he a0o'e formulae can 0e reduced to

? = C"6# J T (#J "D! ) 4 T (hcnt)

=#"/$6 4 hc!#

For free fall condition set the F"7"+ of O- 2hannel 0elow the pipe sill le'el


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Modular Outlets

:KS1L OF P1PK SKM1 MO:;K (!or :1JKCT OT;KT )

@:JA;1C PAJT1C;AJS

:KSCJ1PT1O 1TU PAJT1C;AJS

PAJKT C@AK; OT;KT C@AK;

! 4:acut 4cres 5BG', G5',,

# .ischarge (e>uired.esigned) 2umecs C"#E/C C"E$6C C"CEC C"CEE

E Bed width m !"!CC C"ECC

$ Full 7uppl: .epth m C"CC C"##C

Free 0oard m C"ECC C"ECC

6 7ide slopes (;nner Outer) 8 !"C # 9 ! !"C # 9 !

/ -op width of 0an


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Modular Outlets

.ischarge through the (ipe Outlet 0: using Ori6ce formula9

? = 24 (#g hcnt)!=#where 2 = #" $/6

? = .ischarge of Out +et

4 = 2ross section 4rea of ipe

h(cnt) = &ead of s water surface o'er the center of pipe

? = 24 (#g hcnt)!=#

Where 2 = #"$/6

ro'ide .ia of ipe = 4.cm

4rea 4 = C"C#C m#

? = C"CEE cumec

hcnt = ? 24 #

= C"CEE #"$/6JC"C#

= C"EC m % !" times dia of pipe

Pro2ide did' o! pipe * +,,mm


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&:draulic .esign of 7M

The Center line o! the Pipe * EGE'455 D ,'5, *EG'9,5m

Pipe sill le2el (1n2ert ;e2el) * EGE'455 - ,'5, - ,',9(pipe radius)

* EG'G+5m

@ei"ht o! pipe abo2e C&; * EG'G+5 D EG5'.55 *,',G,m

Pipe in2ert le2el * EG'G+5m

FS; o! 4G-J * EG'G+,m

@ence the pipe is at !ree !all condition

.esignof7M


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; O-+-


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THANK YOU

canal outlets

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