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# Depths Of Flow In Pipe

## Depths Of Flow In Pipe

(OP)

Please excuse lack of knowledge but I am still learning.

If I know a flow in a pipe, plus all the pipe characteristics eg. Grade diameter "n" value how do I establish the depth of flow the get my wetted perimeter.

Where this is leading is I have to prove that I have slime stripping flow and velocity in a sewer pipe. Problem is I know the pipe is not flowing full and I am unclear on how to establish the depth of flow to calculate the wetted perimeter to proceed with my mannings calculation.

Any help would be appreciated.

### RE: Depths Of Flow In Pipe

Calc the HGL through the system.  Assume a reasonable tailwater on the last pipe, work up with loses through the structures.  The HGL approximates the depth of flow.

But if you are just looking for v/vfull relationships, use Q/Qfull to get d/D.  Go to pages 111-113 in this Manual:

Engineering is the practice of the art of science - Steve

### RE: Depths Of Flow In Pipe

Ok, Sounds like you need to establish normal depth in a circular cross section.  This can be done the way lha adresses with v/vfull and nomographs or using math and the properties of circles.  Rather than crunch out the equations now, I will look for the appropiate equations and post them later.

### RE: Depths Of Flow In Pipe

Sorry RjMelbourne for taking so long to get back but here are the eqs i mentioned:

z=D/2-y
A=cos^-1  (Z/r)
P=DA
R=A/P

Y= depth from invert
A=angle from vert to radius matching water surface
Z=center of pipe to water surface (r-y)

Hope this helps I tried to bring in a sketch but could not.

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