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How do I estimate the height of water in an open channel?

How do I estimate the height of water in an open channel?

How do I estimate the height of water in an open channel?

(OP)
Currently I am designing a open flow channel flowing through a screen which is installed at an angle of 70 degrees in the open channel. I have my discharge rate, and the width of the channel. Is there any possible ways that I can estimate the height/depth of the water without knowing the velocity?

RE: How do I estimate the height of water in an open channel?

Most users install an ultrasonic type level transmitter for this application. When the height of the water gets too high, then a signal is sent to the screen to clean itself.

RE: How do I estimate the height of water in an open channel?

Is the question really about calculating depth based on flow or depth based on water flowing over the top of a screen of known dimension positioned at 70 degrees?  If you know your screen dimension, you know the useful cross-sectional area.  Otherwise, I would say, "No, you need to know velocity, differential pressure or some other measurement to cover that 2nd unkown."

Aaron A. Spearin
ASQ CSSBB
www.Engineering6ss.com

"The only constant in life is change." -Bruce Lee

RE: How do I estimate the height of water in an open channel?

(OP)
yes i do know the screen dimension except the height of the screen. But the design is intended to screen water with depth less than the height of the screen and therefore I don't have the height of the water which is my unknown. I tried the approach of giving it a variable H to calculate but I don't seem to get any results from it.

RE: How do I estimate the height of water in an open channel?

Do you have enough information to solve for the area of a hole in the screen?  This could allow you to determine a local velocity.  You would need to know roughly the number of holes in the screen to divide your flow rate.  My appologies, this is the best I can come up with without a picture.  Just some extra food for thought.

Aaron A. Spearin
ASQ CSSBB
www.Engineering6ss.com

"The only constant in life is change." -Bruce Lee

RE: How do I estimate the height of water in an open channel?

Headloss through a screen =

(1/C)((VV-vv)/2g)

where C= headloss coefficient for clean screen = 0.7

V= velocity through clean screen in m/s

v= approach velocity through clean screen in m/s

C= headloss coefficient for clogged screen = 0.6

Assume that a clogged screen has 50% blockage or twice the velocity.

See Metcalf and Eddy Wastewater Engineering

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