Canal Hydraulics Design

VS CONSULTING ( PVT) LTD.

VS CONSULTING ( PVT ) LTD

Calculation of Flow , and velocity with Manning's Coefficient for concrete canal

PROJECT : Gura Small Hydro Power Project 22/ 01/2013

Head race canal - Typical section fro Q= 4.5 m3/s


DESCRIPTION OP -1 OP-2 OP-3 OP-4

Concrete Concrete Concrete Concrete

Notations Lined Lined Lined Lined

DATA INPUT Length of the canal section (m) L 1.00 1.00 1.00 1.00

Depth of flow in the channel (m) d 0.960 1.100 0.550 0.650

Bed width (m) B 2.40 2.40 1.10 1.20

Side slope(left) -(deg) - - - -

Side slope(right)-(deg) - - - -

Bed Slope (m/m) S 0.0030 0.0021 0.0010 0.0030

Roughness coefficient - (Manning's 'n' - See table below) n 0.015 0.015 0.015 0.015

Suggested Minimum freeboard - ( mm) F 300.000 300.000 300.000 300.000

Selected Freeboard - (mm) F 300.00 300.00 300.00 300.00

CANAL Wall height of the canal ( m) H 1.260 1.400 0.850 0.950

DIMENSIONS Depth of flow in the channel (m) d 0.960 1.100 0.550 0.650

Bed width (m) B 2.400 2.400 1.100 1.200

Top width (m) T 2.400 2.400 1.100 1.200

Wetted perimeter (m) P 4.320 4.600 2.200 2.500

Cross sectional area(m2) A 2.304 2.640 0.605 0.780

Hydraulic mean radius R 0.533 0.574 0.275 0.312

VELOCITY Velocity ( m/s)(Manning's equation) V 2.40 2.11 0.89 1.68

FLOW Flow -Q - m3/s Q 5.53 5.57 0.54 1.31

HEAD LOSS Frictional Head loss (m) FHL 0.003 0.002 0.001 0.003

Velocity head loss-(V^2/2xg) VHL 0.29 0.23 0.04 0.14

Transition Head Loss Tr. HL

Total Head Loss THL 0.30 0.23 0.04 0.15

Reynold's Number -Re Re= r/RV/m 1.12E+06 1.06E+06 2.15E+05 4.60E+05

If Re is very high and the flow is rough turbulent zone. So

manning's equation can be applied to the flow.

CRITICAL Normal depth of flow -dn 0.96 1.10 0.55 0.65

DEPTH Critical depth , yc (q2/g)^1/3 0.82 0.82 0.29 0.50

Critical velocity, vc (gyc)^1/2 2.83 2.83 1.69 2.20

Frude number , Fr V/(gd)^1/2 0.78 0.64 0.38 0.66

Velocity of small Waves (gd)^0.5 3.07 3.28 2.32 2.53

Flow condition sub critical sub critical sub critical sub critical

T

B

F

dH


Wall height of the canal ( m) H 1.260 1.400 0.850 0.950

Minimum wall thickness t 1 0.13 0.14 0.09 0.10

Selected wall thickness 0.175 0.180 0.190 0.210

Base thickness 0.175 0.180 0.190 0.210

Concrete volume / m 0.92 1.00 0.60 0.74

Values of n Max. Vel.

Description of channel Maximum Minimum Average

Earth channels, straight and uniform 0.017 0.025 0.0225

Dredged earth channels 0.025 0.033 0.0275

Rock channels,Straight and Uniform 0.025 0.035 0.0330

Rock channels,jagged and irregular 0.035 0.045 0.0450

Concrete lined 0.012 0.018 0.0140

Neat cement lined 0.010 0.013 -----------

Grouted rubble paving 0.017 0.030 -----------

Corrugated metal 0.023 0.025 0.0240

Maximum Velocities to avoid erosion (m/s)


Lined

1.00

1.800

3.60

-

- (0.28) (7,000.00)

0.0030

0.015

300.000

300.00

2.100

1.800

3.600

3.600

7.200

6.480

0.900

3.404

22.06

0.003

0.590

0.593

2.69E+06

1.80

1.56

3.92

0.81

sub critical

T

B

F

dH


2.100

0.21

0.210

0.210

1.73





Weir Hydraulics Badulu oya

h

h

Po

SHARP CRESTED BROAD CRESTED

Coefficient = 1.72 Coefficient = 1.86

Under critical flow condition

Q = C. L. h^(3/2) Q = C. L. h^(3/2)

Q = 8 m/s Q = 363.68 m/s

L = 6 m L = 24 m

h = 0.84 m h = 4.049 m

Ho 1.5 m 1

X Y 2

0.1 0.005 3

0.2 0.017 4

0.3 0.037 5

0.4 0.063 6

0.5 0.096 7

0.6 0.135

0.7 0.180

0.8 0.231

0.9 0.289

1 0.351

1.1 0.420

1.2 0.494

1.3 0.574

1.4 0.659

1.5 0.750

1.6 0.846

1.7 0.948

1.8 1.055

1.9 1.167

2 1.284

2.1 1.407

2.2 1.535

2.3 1.668

2.4 1.806

2.6 2.098

2.8 2.410

3 2.741

3.2 3.093

3.4 3.464

3.6 3.855

3.8 4.265 2.619048

4 4.695

4.2 5.143

4.4 5.611

4.6 6.097

4.8 6.602

5 7.126

5.2 7.668

5.4 8.229

V1^2/2g+H1=V2^2/2g+h2

Dc = 7.208127

Velocity at the top= 8.41

H1= 1 2 3 4 5

V2 = 9.5 10.5 11.4 12.2 13.0

d1 6.4 5.8 5.3 5.0 4.7

Fr No. 1.2 1.4 1.6 1.8 1.9

4.37

OGEE BROAD CRESTED

Coefficient = 2.20 Coefficient = 1.86

q = C. h^(3/2)

q = 60.61

Q = C. L. h^(3/2) Q = C. L. h^(3/2)

Q = 363.68 m/s Q = 2.85 m/s

L = 6 m L = 3 m

h = 9.12 m h = 0.639 m

Curve data po 2

.284Ho 0.426 m Cd = h 1.1

.147Ho 0.221 m h/po 0.55

.235Ho 0.353 m cd 0.522093

.53Ho 0.795 m

.127Ho 0.191 m Q 0.890113

.247Ho 0.371 m

.082Ho 0.123 m

dc= 7.208127 m

6 10

13.7 16.3

4.4 3.7

2.1 2.7

Gravity Weir Design

x2

slope slope

hori 1 hori 0.85

ver 10 ver 1

F 2 3

1

4 5 h2

X

Height of wall (water side) - h1 = 1.5 m

Height of wall (external side) - h2 = 0.35 m

Height of water above the wier (h3) = 1.7 m

Height of water up to wier = 1.5 m

Width of weir top - x2 = 0.6 m

Width of base - X =x1+x2+x3 1.7275 m

Width of the sections at the base level Weight of wall/m

x1 = 0.15 m Section 1 3 kn/m run




Section 5 3 kn/m run

Hydro static pressure at the top of weir = 16.7 kn/m2

Hydro static pressure bottem of the weir = 31.4 kn/m2

Water Force ( F) = 36.05 kn/m run

Pore water pressure= 31.39 kn/m2

Pore Water Force ( F1) = 27.11

Max.sheer force at base = 36.05 kn/m run Max. SF = 36.05 kn/m run

Moments about the toe of F = 24.28 knm/m

Moments about the toe of F1 = 31.23 knm/m

Moments about the toe of W = 67.48 knm/m

Factor of safty =(Moments about the toe of W ) / (Moments about the toe of F+Moments about the toe of F1 ) > 2.0

Factor of safty = 1.2 Over turning satisfied

Sliding = 9.426375 Sliding satisfied

(Moments about the toe of F+Moments about the toe of F1 ) > 2.0

PIPE INTAKE SUBMERGENCE

REFERENCE : GUIDELINES GIVEN BY Gordon, J. L., "Vortices at Intakes," Water Power, April, 1970.

Equation: S = 0.54x Vx (D)^0.5 for straight penstock

Symbol Identification: S - Minimum submergence(m)

V - Vel. of water in the pipe

D - Dia. Of the pipes

Q - Flow ( m3/s)

Q (m3/s)= 0.3

D (m) = 1.1

No. of pipes = 1

V ( m/s) = 0.32

S (m) = 0.18

Free Board (m) = 0

Diametre (m) = 1.1

Clearence to bottom (m) = 0

Add 0.5 FOS to S =0.09

Total Depth (m) = 1.4

Laymen's Manual S > 0.7*D

0.7*D 0.77

Nf =V/(gD)^0.5 < 0.50.0960982

AREA CALCULATION OF A TRASH RACK

Layman's Guidbook

The trash rack is designed to the approach velocity ( V0 ) remains between 0.6 m/s to 1.5 m/s.

The total surface area of the screen will be given by the equation

S= (1/K1)x((b+a)/a)x (Q/V0)x(1/sina)

Where S = evaluate m2 Total area of the submerged part of the screen

Q = 58.00 m3/s Rated flow

V0= 1.00 m/s Approach Velovity( 0.6-1.5 m/s)

1 b= 12.00 mm Bar width

a= 25.00 mm Space between bars

K1= 0.85 Coefficient related to the partial clogging of the scrren

No automatic raker 0.2 -0.3

Automatic raker with hourly programmer 0.4-0.6

automatic raker with differential pressure sensor 0.8 -0.85

a= 70.00 deg. Angle of the screen with the horizontal

Depth of flow = 6.00 m

S= (1/K1)x((b+a)/a)x (Q/V0)x(1/sin 1)

s= 107.47 m2

L = 17.91 m Length of trash rack.

Head loss due to Trash rack

S = m2 Total area of the submerged part of the screen

Q = 58.00 m3/s Rated flow

W = 17.91 m Width of canal

H = 6.00 m Height of flow

V0= 1.00 m/s Approach Velovity

b= 12.00 mm Bar width

a= 20.00 mm Space between bars

Refer Laymens Guidbook K1= 2.42 Coefficient for screen shape ,2.42 for rectangular bars

for K of the other shapes T= 75.00 deg. Angle of the screen with the horizontal

Depth of flow = 6.00 m

Hs = Kx(t/a)^(4/3)x(v^2/2g)sin T

Hs = 0.060 m

Gordon, J. L., "Vortices at Intakes," Water Power, April, 1970.

Coefficient related to the partial clogging of the scrren

automatic raker with differential pressure sensor 0.8 -0.85

Coefficient for screen shape ,2.42 for rectangular bars

SURGE DUE TO SUDDEN STOPAGE OF FLOW IN A CANAL + Revised on : 08/07/2004

BADULUOYA AT DESILT TANK TRASH RACK

Design flow = 1.4 m3/s h+y1 = y2

Width of the canal = 1.2 m h+y1 = 1.25 Change Y2 to equal ( h1+y1)

Flow depth = 0.6 m

V1= 1.9 m/s y2= 1.25

h= 0.65 Surge height

y1 = 0.6 m 2.0 ft

y2= 1.3 m 4.1 ft h

g = 9.81 m/s2 32.2

V1= 1.9 m/s 7.4 fps y1= y2=

V2 = 0 m 0.0 fps 0.6 1.25

If water flowing in a channel with a velocity V is checked instantaneously,

a rejection surge will be produce.

The flow velocity down stream, V1= (y2-y1)x((y1+y2)*g/(2y1y2))^(1/2) ( 1)

Height of the surge , h = cxV(2y1/((y1+y2)xg) (2)

The celarity of the wave, c = ((gy2/2y1)*(y1+y2))^(1/2) (3)

The velocity of the surge wave, Vw = c - V1 ( 4 )

V1= 7.4 fps

(y2-y1)x((y1+y2)*g/(2y1y2))^(1/2)= 7.4 fps

C = 14.3 fps 4.3 m/s

h = 2.1 ft 0.6 m

Rejection wave velocity, Vw= 6.9 fps 2.1 m/s

Length from forbay to the spill, L = 557.8 ft 170.0 m Enter red

Time taken to reach spill, t = 81.3 s .

Surge height , When the canal length is short

Length(m) width(m) Area(m2)

Forebay tank Dimensions5 3 15

5 3 15

Canal ( I ) dimensions170.0 1.2 204

Canal (II) dimensions0 0 0

Total area up to spill 234

Flow enters from the spill to forebay side = 113.88 m3

The surge height = 0.49 m

Weir Hydraulics for side spillway

h

h

SHARP CRESTED BROAD CRESTED

Coeffi = 1.72 Coeffic= 1.75

Under critical flow condition

Q = C. L. h^(3/2) Q = C. L. h^(3/2)

Q = 1.3 m/s Q = 1.3 m/s

L = 10 m L = 10 m

.

h = 0.18 m h = 0.18 m

Assuming all

filamental

velocities in

the bend are

equal to the

mean

velocity Vz

and that all

streamlines

have a radius

of

curvature,rc ,

and a simple

formula for

superelevatio

n is given by

,

h = Vz^2*b/(g*rc) Minimum radius r min = ( 3*b ) m

Vz = 1.9 m/s r min = 3.6 m

b= 1.2 m

g = 9.81

rc= 15.55556 m

h = 0.030 m

Radius Velocity super Elev.

10 2.5 0.09 m

15 2.5 0.06 m

20 2.5 0.045 m

25 2.5 0.036 m

Calculation of surges in sloping canal

Length of the canal section = 300 ft

Slope = 0.003

No of sections = 2

F = 0.45 ft F= 0.45

At the step, the surge travelling upstream is given by,

(V1-V2)^2 = (y1-y2)^2 (y1+y2)*g/(2y1y2) ( 1 )

At the step, the surge travelling downstream is given by,

(V ' 1-V ' 2)^2 = (y ' 1-y ' 2)^2 (y ' 1+y ' 2)*g/(2y'1y'2) ( 2 )

At the step, hydraulic continuity,

V2y2 =V ' 2y' 2 ( 3 )

V1= 7.4

Assumed values = V2 = 0.38

(V1-V2)^2 = 49.40

y1 = 2.0

y2 = 5.3

(y1-y2)^2 (y1+y2)*g/(2y1y2) = 121.03

y'1 = 4.1

y2 = 5.25

F = 0.45

(y ' 1-y ' 2)^2 (y ' 1+y ' 2)*g/(2y'1y'2) =17.25

V ' 2 = 17.25

V 2xy2 = 2.0

V ' 2 x(y2+F) = 98.3

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Revised on : 08/07/2004

Change Y2 to equal ( h1+y1)

Surge height

m

0.51

OGEE

Coeffit = 2.20

Q = C. L. h^(3/2)

Q = 1.3 m/s

L = 10 m

h = 0.15 m

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RESULTS CHEKED Calculation of Flow , and velocity with Manning's Coefficient.

THERE ARE HIDDEN CELLS !!!

Chainage From

Box canal hydraulics


Length of the section (m) l

Height of the channel with free board (m) H

Bed width (m) B

Side slope(left) -(deg)

Side slope(right)-(deg)

s

s

Bed Slope (m/m) S

Roughness coefficient - (Manning's 'n' - See table below) n

Freeboard (mm) F

Depth of flow in the channel (m) d

Bed width (m) B

Top width (m) T

Wetted perimeter (m) P

Cross sectional area(m2) A

Hydraulic mean radius R

Frictional Head loss (m) FHL

Velocity head loss-(V^2/2xg) VHL

Transition Head Loss Tr. HL

Total Head Loss THL

Velocity ( m/s)(Manning's equation) v

Flow -Q - m3/s Q =

Reynold's Number -Re Re= r/RV/m

If Re is very high and the flow is rough turbulent zone. So manning equation can be applied to the

flow.

Normal depth of flow -dn-(m)

Critical depth , yc (q2/g)^1/3

Critical velocity, vc (gyc)^1/2

Frude number , Fr V/(gd)^1/2

Velocity of small Waves (gd)^0.5

Flow condition

Minimum freeboard = mm

Head loss due to transitions

No.

1

2

3

Type of transition 1

Factor 0.05

Velocity before the transition

Velocity after the transition

Tr. Head Loss-m

Description of channel

Earth channels, straight and uniform

Dredged earth channels

Rock channels,Straight and Uniform

Rock channels,jagged and irregular

Concrete lined

Neat cement lined

Grouted rubble paving

Corrugated metal

Calculation of Flow , and velocity with Manning's Coefficient.

Lined Lined Lined Lined Lined Lined

2136.3237

1000.0 1000.0 1,000.00

115.00 115.00 115.00 1,000.00 1,000.00 1.00 1.00 1.00 1.00

1.200 1.200 0.600 0.650 4.000 0.750 0.800 0.850 0.900

1.60 1.60 1.20 1.30 15.00 1.50 1.60 1.70 1.80

- - - - - - - - -

- - - - - - - - -

0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

1.200 1.200 0.600 0.650 4.000 0.750 0.800 0.850 0.900

0.0035 0.0035 0.0040 0.0027 0.0010 0.0022 0.0020 0.0018 0.0017

0.015 0.015 0.015 0.015 0.035 0.015 0.015 0.015 0.015

200.00 200.00 200.00 200.00 200.00 200.00 200.00 200.00 200.00

196.24500

1.00 1.00 1.31 0.45 3.80 0.55 0.60 0.65 0.70

1.60 1.60 1.76 1.30 15.0 1.5 1.6 1.7 1.8

1.60 1.6 1.8 1.3 15.0 1.5 1.6 1.7 1.8

5.200 3.6 4.4 2.2 22.6 2.6 2.8 3.0 3.2

1.600 1.600 2.297 0.585 57.000 0.825 0.960 1.105 1.260

0.308 0.4 0.5 0.3 2.5 0.3 0.3 0.4 0.4

0.403 0.403 0.46 2.74 1.00 0.00 0.00 0.00 0.00

0.16 0.27 0.38 0.11 0.14 0.11 0.11 0.11 0.11

0.01 0.01

0.58 0.67 0.84 2.85 1.14 0.11 0.11 0.11 0.11

1.80 2.30 2.75 1.44 1.67 1.46 1.46 1.46 1.46

2.87 3.67 6.31 0.84 95.45 1.20 1.40 1.61 1.85

0.80 0.85 0.90

4.85E+05 8.95E+05 1.27E+06 3.37E+05 3.70E+06 4.05E+05 4.38E+05 4.71E+05 5.06E+05

1.00 1.00 1.31 0.45 3.80 0.55 0.60 0.65 0.70

0.69 0.81 1.09 0.35 1.60 0.40 0.43 0.45 0.47

2.60 2.82 3.28 1.85 3.97 1.99 2.05 2.10 2.16

0.57 0.73 0.77 0.69 0.27 0.63 0.60 0.58 0.56

3.13 3.13 3.58

sub critical sub critical sub critical sub critical sub critical sub critical sub critical sub critical sub critical

300.000

Head loss due to transitions

Type of Tran. Factor

Bell mouth 0.050

enter No. here

1.00

2.00

0.008

Values of n Max. Vel. Material Less than .3 m deepLess than 1.0 m deep

Maximum Minimum Average

0.017 0.025 0.0225 Sandy /loam 0.40 0.50

0.025 0.033 0.0275 Loam 0.50 0.60

0.025 0.035 0.0330 Clay Loam 0.60 0.70

0.035 0.045 0.0450 Clay 0.80 1.80

0.012 0.018 0.0140 Masonry 1.50 2.00

0.010 0.013 ----------- Concrete 1.50 2.00

0.017 0.030 -----------

0.023 0.025 0.0240


10.00 11.00 12.00 13.00 14.00 15.00 16.00 17.00

1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00

0.950 1.000 1.100 1.200 1.300 1.400 1.500 1.600 1.700

1.90 2.00 2.20 2.40 2.60 2.80 3.00 3.20 3.40

- - - - - - - - -

- - - - - - - - -

0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

0.950 1.000 1.100 1.200 1.300 1.400 1.500 1.600 1.700

0.0016 0.0015 0.0012 0.0012 0.0011 0.0010 0.0009 0.0008 0.0008

0.015 0.015 0.015 0.015 0.015 0.015 0.015 0.015 0.015

200.00 200.00 - - - - - - -

0.75 0.80 1.10 1.20 1.30 1.40 1.50 1.60 1.70

1.9 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4

1.9 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4

3.4 3.6 4.4 4.8 5.2 5.6 6.0 6.4 6.8

1.425 1.600 2.420 2.880 3.380 3.920 4.500 5.120 5.780

0.4 0.4 0.6 0.6 0.7 0.7 0.8 0.8 0.9

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

0.11 0.12 0.12 0.14 0.14 0.14 0.14 0.13 0.15

0.11 0.12 0.12 0.14 0.14 0.14 0.14 0.14 0.15

1.48 1.50 1.55 1.64 1.66 1.66 1.65 1.62 1.69

2.11 2.41 3.75 4.73 5.61 6.51 7.43 8.32 9.78

0.95 1.00 1.10 1.20 1.30 1.40 1.50 1.60 1.70

5.43E+05 5.86E+05 7.48E+05 8.65E+05 9.46E+05 1.02E+06 1.09E+06 1.14E+06 1.26E+06

0.75 0.80 1.10 1.20 1.30 1.40 1.50 1.60 1.70

0.50 0.53 0.67 0.73 0.78 0.82 0.86 0.88 0.94

2.22 2.28 2.56 2.68 2.77 2.84 2.90 2.94 3.04

0.54 0.54 0.47 0.48 0.46 0.45 0.43 0.41 0.41

sub critical sub critical sub critical sub critical sub critical sub critical sub critical sub critical sub critical

0.0 0

1,520.0 1520

18.00

1.00

1.800

3.60

-

-

0.000

0.000

1.800

0.0007

0.015

-

1.80

3.6

3.6

7.2

6.480

0.9

0.00

0.14

0.14

1.64

10.65

1.80

1.30E+06

1.80

0.96

3.07

0.39

sub critical

FLOW VELOCITIES


Material < .3 m deep < 1.0 m deep

Sandy /loam 0.40 0.50

Loam 0.50 0.60

Clay Loam 0.60 0.70

Clay 0.80 1.80

Masonry 1.50 2.00

Concrete 1.50 2.00

0.0003 0.00065

1000 350

0.3 0.2275

996.55

994.95

994.2

0.75

1153.84615

Calculation of orifice size

At the sluice the flow velocity is given by

Dh = V2^2/(2g) ------- ( 1)

V = (Dhx 2g)^0.5 ------- (2)

D & W Calc. for Design flow. When the width of the sluice opening is -W . 1.40 m

Depth of sluice opening -D1 0.60 m

The flow through the sluice is , Q 2.01 m3/s

Limit the velocity of the flow through the

sluice to , V -m/s 3.00 m/s

Using eqn (1) , the Dh = 0.51 , when V=

The depth of flow under the sluice , D1 = 0.60 m

Q =0.6A(2gh)^0.5 , where h is the depth to the

centre of the orifice. Dh=

h ( m ) = 0.81

Q (m^3) = 2.01

FLOW DEPTH CALC .

C c = 0.60

CcxD1= 0.36

V1= 3.99

The Frude No. F=V1/(gD1)^0.5 at the

D1 = 2.12

h= Dh = 0.5799

D1 = 0.45

m/s

0.6

h=

0.51 h= Dh = 0.5799

D1 = 0.45

m/s

0.6

Broad crested weir The weir formula can be applied to the weir to calculate the discharge , if the flow over the weir is critical

d c = ( q^2/g) ^( 1/3) , q is the flow pe runit width

Vc = ( gdc) ^0.5

The total energy at the weir shall be calculated to check the critical condition.

Drawing is here

Specific energy U/S of the weir E 1

E1 =( V^2/ 2g) + H1 + Po

Specific energy U/S of the weir E 1

EC =( Vc^2/ 2g) + Hc + Po

For known Q , and width of a weir ( W)

d c = ( q^2/g) ^( 1/3) , q is the flow per unit width

Vc = ( gdc) ^0.5

Q 1.3 m3

W 3 m

q 0.43 m3/m

dc = 0.27 m

vc = 1.62 m/s

( Vc^2/ 2g) + dc = 0.40 m

EC =( Vc^2/ 2g) + Hc + Po

Assume E1 =( V^2/ 2g) + H1 + Po = 1

P0 = 0.60 m

The floor has to be raised by 2.00 m to flow go under critical

FOR BROAD CRESTED WEIR THE DISCHARGE IS GIVEN

Q = C. L. H ^(3/2)

Coefficient = 1.70

Q = 1.30 m/s

W= 3.00 m

H = 0.40 m

dc * 1.5 = 0.40 m

Cd discharge correction factor ( for short weirs) ( by Chow 1988)

Cd = ( 0.65/ ( 1 + H/ P0)^0.5 )

H/ Po = 0.20

( 1 + H/ P0)^0.5 ) = 1.10

cd= 0.59

H = 0.62 m

The weir formula can be applied to the weir to calculate the discharge , if the flow over the weir is critical

Hina Rabbani KharDesign of Forebay and quantities

Designed flow = m3/s 1.5

Velocity through the pipe ( Vp) = m/s 2.36

Width of the entrance Canel (W1) = m 1.20

Height of the entrance Canel (H1) = m 0.60

Diametre of the pipe ( d)= m 0.90

Rock excavation percentage = 0.3

Depth of water above the penstock pipe (df) = m 2.70

Free board( F) = m 1

Total depth of the tank = m 4.90

sectio

n 1

sectio

n 2

Flow through the trash rack Length 3

Thickness of the trash rack members= mm 12

Spacing of the members= mm 20 Free board= 1.10

Velocity through the trash rack = m/s 0.75 Canal depth = 1.00

Covered width = m 1.3125

Width of the tank = m 3.5 Section 2 depth = 2.66

Clear width at the t. rack= m 2.1875 Section 4 depth = 3.21

Ht. of the trash rack below water = m 0.9

Separation wall height = m 1.2 Section 5 depth = 4.90

QUANTITY CALCULATION

Concrete

Wall top depth = m 0.2

Wall slope = deg 4

Wall sec 1 ht. = m 2.10


Thickness at sec-2= m 0.40

Length = m 3

Wall concrete volume = m3 4.26

Length of base = m 3.05

Base concrete = m3 2.85


Wall slope = deg 4




Length = m 3





Wall slope = deg 4




Length = m 6





Wall slope = deg 4




Length = m 6


Area of base = m 21.00



Wall slope = deg 4




Length = m 3.5


Walk way depth = m 0.2

Walk way length = m 39.5

Width of walk way = m 0.80

Walk way Wall concrete volume = m3 6.32 6.32

Trash rack beam length = m 3.50

Width of beam = m 0.40

Depth of beam = m 0.60

Concrete volume = m 0.84

Anchor block next to forebay



Concrete volume = m 3.00 3.00

Beam right round section 4



Length = m 16.80 5.67

Total wall concrete = m3 97.89

FORMWORK



Length = m 3

Wall formwork area = m2 28.54



Length = m 3




Length = m 6




Length = m 15.5



Length = m 3.5


Walk way depth = m 0.2

Walk way length = m 39.5

Width of walk way = m 0.80


Trash rack beam length = m 3.50



Concrete volume = m 5.60

Anchor block next to forebay



Concrete volume = m 3.00 9.00

Beam right round section 4



Length = m 13.30 15.96

Total form work quantity = m2 366.24

Reinforcement = kg 9,789.18

Excavation m3 315

Rock excavation m3 0.945

screed concrete m2 75.6

Capacity of Forbay

Flow - Q(m3/s) =

Pipe diameter =

Appo. water level (minimum) above penstock pipe =

Time of capacity required turbine operation =

Capacity of FORBAY tank =

Dimention of Forbay (Effective Area)

sectio

n 3

sectio

n 4

sectio

n 5 Length =

3 6 6 Height above the water =

Width =

Volume =

Sedimantation tank

OPTION

Width - (m )

Length - (m)

Height -(m)

Sedimentation tank capacity

1.69

Canal capacity

0.275 11 3 9.075

1.5

0.90 m

2.7 m ( to prevent vortex forming)

0.5 min

45 m3

9 m

1 m

4 m

36 m3

2 160 187 212

253

6

12.2

1.2

65.88 m3

101.88 m3

0 m

0.6 m

3.6 m

0 m3

VS Consulting ( Pvt) Ltd.

Calculation of Dimensions of a sedimentation tank

PROJECT: Bulath watha

1

Designed flow = m3/s 6.80

Max . Flow Velocity through the tank ( Vh) = m/s 0.3

Width of the entrance Canel (W1) = m 2.0

Width of the exit Canel (W2) = m 2.0

Maximum size of particle to be settled = mm 0.300

Settling velocity of particle in still water ( Vs) = m/s 0.040

SAY, W(idth)of the settling tank= m 5.0

Area of Sedimentation tank = m2 22.7

Height of the approach canal = m 1.13

D settling at mid length = m 4.5

The settling (Detention ) time " t " = Sec. 113.5

Length of settling = m 34.1

Length of transition

L- entrance ( 1v:8h)= m 12.0

L exit (1v: 5h) = m 7.5

Total length of Sedimentation tank ( L) = m 54

Sedimentation Depth = m 4.50

Sediment depth = m 1.5

Freeboard = m 0.4

Total depth = m 6.4

Sedimentation Volume(if rectangular base) =m3 255.75

the effect of turbulence

V1= 0.0185852

l = 0.591561

PARTICLE SIZE (mm) Settling V, vel. (m/s) V2

0.1 0.001 -0.0175852

0.2 0.025 0.006414799

0.3 0.04 0.021414799

0.4 0.054 0.035414799

0.5 0.065 0.046414799

0.7 0.085 0.066414799

CALCULATIONS

APPROXIMATE DIMENSIONS OF THE SEDIMENTATION TANK

Only the settling tank has been considered with a flat land.

Height of excavation is same as the tank height.

Wall thickness at top -t0(m) 0.2

Wall thickness -t1 (m) 0.54

Base thickness-t2 (m) 0.67

Rock as a % of excavation = 30

Extra width for exca. 0.6

Extra width for screed 0.3

Description Rate Qtty.

Excavation m3 500 1,235.15

Trimming of base ext. m2 250 248.25

Rock or hard soil m3 1650 370.54

Screed concrete m2 950 295.78

Concrete in wall m3 11500 229.97

Concrete in base m3 11500 189.37

Form work in wall m2 600 1,117.56

Form work in base m2 600 170.50

R/F -140 kg./m3 of conc. kg 115 58,707.67

Water bars lm 600 12.75

Rubble work to form the sluce channel m3 5000 180.90

smooth Plastering m2 250 265.32

Infill concrete in tank base sqm 333.49

Flusing canal m 10000 40.00

Gate Nos. 1

Contingencies 5%

Total

SPILL = <8000>

60°

SECTION A-A

A

1000.770

EXPANTION JOINT

30

0

30

00

500

FLOW

11

00

16

89

800

36

20

40

00

999.800

12

50

35

00

47

70

EXPANTION JOINT

TRASH RACK

1000x1000 SILT REMOVAL GATE

PLAN

A

.3000

R/F CONCRETE PAVING AT GROUND LEVEL

600

800

75

0

1000

10

00

250

16

00

50

00

998

20

1000

Amount

617,573.11

62,062.00

611,397.38

280,989.10

2,644,641.20

2,177,774.69

670,536.00

102,300.00

6,751,382.24

7,650.00

904,500.00

66,330.00

400,000.00

400,000.00

15,297,135.72

764,856.79

16,061,992.51

Capacity of Forbay

Flow - Q(m3/s) = 8Pipe diameter = 1.53 m

Appo. water level (minimum) above penstock pipe = 2.3 m

Time of capacity required turbine operation = 0.45 min

Capacity of FORBAY tank = 216 m3

Dimention of Forbay (Effective Area)

Length = 20 m

Height above the water = 2.1 m

Width = 4 m

Volume = 168 m3

Sedimantation tank

OPTION 2

Width - (m ) 6

Length - (m) 12.2

Height -(m) 1.2

Sedimentation tank capacity 65.88 m3

233.88 m3

Canal capacity 0 m

0.6 m

3.6 m

0 m3

SPILL = <8000>

60°

SECTION A-A

A

1000.770

EXPANTION JOINT

30

0

30

00

500

FLOW

11

00

16

89

800

36

20

40

00

999.800

12

50

35

00

47

70

EXPANTION JOINT

TRASH RACK

1000x1000 SILT REMOVAL GATE

PLAN

A

.3000

R/F CONCRETE PAVING AT GROUND LEVEL

600

800

75

0

1000

10

00

250

16

00

50

00

998

20

1000

( to prevent vortex forming)

160 187 212

253

Canal Hydraulics Design

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