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ISMA proposes two kinds of Venturi Flumes

 

ISMA Venturi flumes - exponential cross section
ISMA Venturi flumes - rectangular cross section
 


 

ISMA Venturi flumes with exponential cross section

The originality of ISMA Venturi flumes is to hold the classical Venturi flumes advantages and to be able to adapt to important flow variations. In fact, the contracted form is a parabolic cross section, the col opens out from the basis to the top.
This particularity allows the low flow to measure with accuracy, as the reduced flowing forwards through a tight section, basis of the parabolic form.
When the flow grows up, the section broaden until the top, releasing progressively an important wet section.

For that reason, this Venturi type is the only one to allow the accurate measure of variable flow in an extreme proportion from 1 up to 100. For example, for the V size: the continuous measuring possibility spreads from 3,6 m3/h up to 360 m3/h. This proportion is generally only from 1 up to 30 for the classical Venturi flumes. This faculty answers to the request of ideas men and industrialists, even if there is an erroneous or uncertain estimation of the volumes to measure. Its interests are to allow the measure of throws subjected to large flow variations, either for instantaneous flow (fast draining of spillways stock) without any prejudicial overflowing to the industrial activity, or in unitary mains for the community at the time of flow peak (storm rain). There are 7 different types of ISMA Venturi flumes exponential cross section, allowing to measure by staged ranges from 0, 22 m3/h up to 1400 m3/h. Manufactured in polyester and reinforced in fiberglass, they present a very low roughness coefficient, a resistance to aggressive and charged effluents, its strength ensured by crossing wire stretchers, for a direct implantation in concrete formwork.

ISMA proposes a range of 7 Venturi flumes :
Made in polyester and fiberglass and with SHORT flumes
Colour: RAL 5015

Water height column graphics

Flume type 1.
Flume type 2.
Flume type 3.
Flume type 4.
Flume type 5.

Flume type 6.

Flume type 7.
 


 

Description
Type    I
Type II
Type III
Type IV
Type V
Type VI
Type VII
A Right lenght upstream to respect
900
1300
1900
2800
4200
5500
7300
B Inner width 
90
130
190
280
420
550
730
C Cross bars width
25
30
40
50
80
100
140
D Right length in channel
455
575
725
880
1080
1100
1460
E Thickness
4
4
5
5
7
8
10
F Measuring point
486
627
798
1014
1260
1800
2400
M Overall width
150
190
260
360
520
720
910
H Inner height
200
250
310
380
460
600
800
L Overall length
750
1000
1350
1800
2500
3150
4200
P Width of long reinforcements
30
35
40
50
50
55
60
   
l/s
m3/h
l/s
m3/h
l/s
m3/h
l/s
m3/h
l/s
m3/h
l/s
m3/h
l/s
m3/h
Q Minimum flow
0,06
0,22
0,12
0,43
0,25
0,90
0,5
1,80
1
3,60
2
7,20
4
14,4
Q Maximum flow
6
22
12
43
25
90
50
180
100
360
200
720
400
1440

 

  Calming approach flumes for exponential LONG Venturi flumes

Type
Length 
in mm
Inner width 
in mm
Inner height 
in mm
I
900
90
200
II
1300
130
250
III
1900
190
310
IV
2800
280
380

 

 


 

ISMA Venturi flume with rectangular cross section


Measuring method principle for Venturi flume.

A symmetric contracted form of the flume bed drives the measured liquids back and increases the flowing speed in the restricted section.

The difference between the upstream and downstream levels at the right of the minimal section is a flow measure.

In practice, the flow only depends on the upstream level h1.

On the hypothesis that the measuring section frame is horizontal and if the disturbances due to the downstream level are insignificant (flowing back, superficial waves), the Bernoulli theorem and the continuity equation give, for the Venturi flumes with measure and narrow part rectangular section, the following relation :
 

Q = c.h1^1,5

 with :

Q= flow
c= constant flow coefficient

h1= upstream level

 
Type
Q max (m3/h)
Width B (mm)
Contraction B2 (mm)
150/75
28
150
75
200/100
56
200
100
250/125
100
250
125
300/150
156
300
150
400/200
322
400
200
500/250
560
500
250
600/300
890
600
300
700/350
1300
700
350
700/420
1600
700
420
800/400
1800
800
400
900/450
2400
900
450
1000/500
3200
1000
500
1500/750
8000
1500
750
2000/1200
10000
2000
1200

 

For other water height column graphics and other dimensions, please contact us.

 


 
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