Discharge of a partial full pipe 1

[GEshel]

Shalom,

I'm trying to calculate the discharge of a short (few meters), partial full concrete pipe that fids/discharge directly from/to open channels (i.e. continuous flow, no free fall).
Measuring the water velocity is not possible because of floating debris that can block the sensor. I think I can use the Manning equation by measuring the head loss between the inlet & outlet of the pipe, but I have few questions about it:
1- Is it the right method?
1- Is it correct to use this method when the head exceeding the pipe radii?
2- Is there an alternative way to calculate the discharge by only measuring one point?

Thanks for the help,
Gonen Eshel

 

[blueoak]

Are you going to want to measure here for awhile with pretty good accuracy? The best reference is the USBR Water Measurement Manual Edition 3 free for download.

There are lots of sensors.
They make good velocity meter that sits above the water that with a bubbler to measure stage give good continuous measurements. Also you can form a flume in the pipeline (see USBR long throated for the best guidance) and measure with a staff gage or bubbler. For long term the Winflume program by USBR can design a nice little sill that can be prefabricated for field installation. It also will print out a staff gage and calculate expected accuracy.

A quick give or take 15% method is to use an orange. drop it in on side time it. Then using USGS guidance multiply the resulting velocity by a flow factor, about 0.8.(open channel flow)This is my favorite though I end up using a tennis ball most of the time, I hate to waste an orange (Crack it and let in a little water to get it to submerge more.)

A method out of Utah includes sticking a stick (graduated) and measuring the rise of water on the front side. If interested I can look for the info.

 

[GEshel]

Blueoak hi,

Thanks for the info about WinFlume, I'm trying to use it.

My task is to calculate the discharge of the mentioned pipe by continuously measure the head in one point (only one device in the field right now) or two points (optionally) with minimal arrangements.
Again, I think I can consider the lower half of the pipe as a channel and use the Manning equation. What I'm not sure is if I can use this method while the water flows in the upper half.
Any suggestions are welcome.

Thanks again,
Gonen Eshel

 

[blueoak]

If you have the budget ISCO meters like the one below are really the easiest and nicest. Weirs are good but have some drawback. I definetely recommend reading the USBR Water Measurement Manual (or skim). It will give you the best options for your situation.

http://www.isco.com/products/products3.asp?PL=2023040