Parshall Flume

It is really hard to answer without particular data.

But, be advised that even with some distance, you could have what we call a completely developed flow, and it still be turbulent. Turbulency itself is not a problem in a wide range of applications... Actually you'll rarely see a linear flow.

Tell us what's your practical problem.

Typical upstream distance is around 6 times the throat width.The sensor (ultrasonic, bubble tube, etc.) should be placed 2/3 of the distance of the throat width upstream from the beginning of the throat.

The formula for calculating flow rate for Parschall Flume is :take the square root of the cube of the height, in percent., to obtain percent of full flow.The full flow should be specified in the design of the Flume.A flow data chart should have been included if this is a manufactured flume, rather than a field fabricated unit.

Is this for influent, or effluent flow? If so, be aware that foam can sometimes create errors with certain ultrasonic sensors.

Does this help?

HiTekRedNek

Since R. L. Parshall invented his flume, he do it for a critical regime flowmeter, this mean that the flume works in this kind of flow conditions, any way in order to answer your question we need to know the size of the throat and if the flume is in submergence.

Regards

If you are looking for a flow rate, in gallons, liters,etc, and do not know what to expect,we do need to know dimensions in order to help you.Regardless, the instructions regarding upstream distance and placement of the measurment device are the same, regardless of the flume size.

There are other flume designs besides parschall...are you sure of the type that you have? It will have a dramatic effect on flow, because some flumes use a 5/3 power to determine flow, and there are even more uncommon ones that are proprietary.

How we can design Parshall flume for 10 MLD - 125 MLD flow?

It is very tediuos and complicated to actually field-make a flume with the accuracy of a factory-made fiberglass form.Check out the link below for information.There are also specificatiions included if you insist on making the flume yourself.

http://www.tracomfrp.com/parshall.htm

Hope this helps.

HTRN

An additional reference I forgot to mention before is:

http://www.usbr.gov/pmts/hydraulics_lab/pubs/wmm/

Good luck!

HTRN

thnks for all your efforts ,we have taken 6 times the throat width in upstream.

regards

Vishal

According several reliable references, the straight channel upstream distance should be at least 10 times the Parshall throt width, but if there is some turbulence strong contributor (like a restrictive or adjustable gate), then this distance must be increased in consequence; for instance, until not "white" water alike is present (it means water with bubles). I hope I could help or make broader your doubts. E-mail me and I can send you more information about Parshall's. Regards. Cassiano H. Conzatti, Instrumentation Engineer cassianohc@pcd.com.mx