Stage storage question

[dwitczak]

I need to compute the stage storage of several different ADS pipes which will be laid on a slope. Does anyone have an excel or other program that will generate the stage storage calculations?

 

[gbam]

I am not sure what a ADS pipe is but as to your question about a spreadsheet, I would code your own to be sure that it correctly calculates the storage.

There is a program that will route the hydrograph for you from FHWA - Urban Drainage Design, HY-22

 

[LHA]

I would post this on the "AMS: HydroCAD Stormwater Modeling System" Forum. I'll bet Peter Smart has a quick, free solution...

 

[darth051]

Stage-storage in sloped pipes is not the easiest calculation to do. Luckily for me I use MIDUSS for my stormwater designs and analysis and it includes pipe storage as an option and calculates it for me. (As well as parking lot storage and normal storage in ponds.)

That said, while MIDUSS does the calculations it runs for about $800US or $900US.

 

[gbam]

The Program I mentioned will also calculate the stage storage of sloped pipes.

 

[JasonG]

Check the technical section of their website. If I remember correctly, they have a spreadsheet and/or info on these calculations.

http://www.ads-pipe.com/us/en/index.shtml

If not, there are tables and graphs in the literature for computing the cross sectional area of a partially filled pipe. They would work if the slope is small enough that any change in the volume could be neglected. Otherwise you could average the cross sectional areas between the two ends of the sloping pipe.

 

[bltseattle]

I have a spreadsheet tool to do this. The answer is more accurate if you break the pipe length into segments because average end area is not totally mathematically correct unless the pipe is totally full, it can be off as much as 5% at low stages.

I could send you the tool but don't have much time to explain it. Alternatively, attached below is a VBA code for a custom Excel function you can use to develop your own tool. Another approach is to construct a partially full pipe lookup table (such as the one found in the Civil Engineering Reference Manual (Lindebergh) 6th Edition Chapter 3 Appendix E), if you are willing to type in the 100 values.

User Defined Function for Partially Full Tank:
Depth = depth of water measured from invert to water surface
Diam = diamter of tank
Units must be the same for depth and diam.


Public Function part_full_circ_area(depth, Diam) As Double
' This function will determine the area occupied when a circular section is partially filled.
' Prepared by Brian Taylor, April 2004
'
Dim arg1, eval_asin As Double
'
Const pi = 3.14159265
' Screen out very low values. Precision is limited to input depths greater than 1E-16
If depth <= 0.000000000000001 Then
part_full_circ_area = 0
Else
If depth >= Diam Then
part_full_circ_area = pi * Diam ^ 2 / 4
Else
' The following code computes the arcsin(1-2d/D).
' Note that Visual Basic does not have a function for arcsin.
' The following derived function is used: Arcsin(X) = Atn(X / Sqr(-X * X + 1))
arg1 = 1 - 2 * depth / Diam
eval_asin = Atn(arg1 / Sqr(-arg1 * arg1 + 1))
'
' Now apply the area formula:
' A = pi*D^2/8 - D^2/4*arcsin(1-2d/D)-(D/2-d)*sqr(d(D-d))
'
part_full_circ_area = pi * Diam ^ 2 / 8 - Diam ^ 2 / 4 * eval_asin - (Diam / 2 - depth) * Sqr(depth * (Diam - depth))
End If
End If
End Function


Reference:

http://mathforum.org/library/drmath/view/55223.html