Open Channel Flow Measurement

S

Thread Starter

SAVAS YILMAZ

Hi All,

We need to measure the water flow in an open channel. We have a level
transmitter. We want to see the flow that changes with height linearly.
Which shape can we make a notch that give the flow, with level. Flow is in
35 m3/hour. Level transmitter is measuring 0-35 cm range.

Do you have an idea how shape of notch must be?


Best Regards,
Savas Yilmaz
Instrumentation Engineer,
Soda Sanayii A.S. Kromsan Plant
Mersin, Turkey.
Tel: +90 324 451 34 34 (internal) 355
 
D

David W. Spitzer

Savas,

You mention a notch, so I assume that you are going to use a weir. Depending
on the shape, weirs have flow characteristics where the flow is proportional
to the 1.5 and/or 2.5 power of the level. Turndown should play a part in
which shape is selected. If there is insufficient head available, consider a
flume. A level transmitter with built-in flow algorithms should be
considered.

For more information, see Industrial Flow Measurement (ISA) and Flow
Measurement (ISA).

Regards,

David W Spitzer, PE
Copperhill and Pointer, Inc.
http://www.icu.com/spitzer845.623.1830 (phone/fax)
 
W
You can use either a rectangular weir, a trapezoidal weir or a v-notch weir.
You should reference the USDA Bureau of Water Reclamation Flow Handbook,
which is entirely available on line at: http://www.usbr.gov/wrrl/fmt/wmm/ or
get a copy of the ISCO Flow Handbook, most current edition, from ISCO Inc.
at www.isco.com.

Walt Boyes
Applications Columnist
Flow Control Magazine
 
W

Wayne Shimanis Vortex Technologies, Inc.

Mr.Yilmaz:

A 22.5 degree V-Notch Weir at a head of 0.265 meters (26.5 cm) will read
35.71 cubic meter\hour. A fabricated V-Notch of 35 cm is within a reasonable
range for your application. At 35 cm the flow meter should read 71.59 cubic
meters/hr.

Wayne Shimanis
Vortex Technologies, Inc.
815-254-9400
 
Hi Savas

We did something along the lines of your situation that should work for you. This is off the subject a bit – but necessary to give you a feel for the project.

Our cottage lake has only one exit stream or drain. Beavers have had dams forever, on the outlet keeping the level too high and stopping the flow. We break the dam they build it, we transfer the beavers – new ones arrive.

So finally we figured out that if we notch the dam, drop in a pipe with a muzzle type screen, put the inlet far enough up stream so they can’t hear the flow – we got em beat. The level of the pipe dictates the water level and they can build the dam as high as they want.

So Savas – your best bet might be to install a e.g. 1 ½” plastic pipe in the dam, wall or side with a tee to insert a flow meter. Set the pipe accordingly and it is adjustable.

We should have a picture on www.brandylake.com of this device early next week. July 17. 01.

Our level and flow page is www.almegcontols.com

Thanks Bob Hogg




> Hi All,
>
> We need to measure the water flow in an open channel. We have a level
> transmitter. We want to see the flow that changes with height linearly.
> Which shape can we make a notch that give the flow, with level. Flow is in
> 35 m3/hour. Level transmitter is measuring 0-35 cm range.
>
> Do you have an idea how shape of notch must be?
>
>
> Best Regards,
> Savas Yilmaz
> Instrumentation Engineer,
> Soda Sanayii A.S. Kromsan Plant
> Mersin, Turkey.
> Tel: +90 324 451 34 34 (internal) 355
 
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