| Product(s): |
SewerGEMS, SewerCAD, CivilStorm, StormCAD |
| Version(s): |
08.11.XX.XX, 10.XX.XX.XX |
| Area: |
Calculations |
Problem
How is the effective shape or flow area calculated when using the Catenary conduit section shape? The related help topic indicates that a cosine function is used but does not explain how the a and b coefficients are determined.
Solution
A rating table is used in place of cosine coefficients, to determine the cross section area of a partially filled catenary arch pipe. This rating table is shown below. This follows the same calculation procedure as EPA-SWMM. For example, with the tabular data below, the width of flow is derived in the pipe given the depth in the pipe.
With the ratio points below, the cosine coefficients can be back-calculated if needed.
Note that the Width of the catenary pipe is equal to 2/5 of the height.
|
Depth/FullDepth
|
Width/MaxWidth
|
|
0.00
|
0.0000
|
|
0.05
|
0.6667
|
|
0.10
|
0.8222
|
|
0.15
|
0.9111
|
|
0.20
|
0.9778
|
|
0.25
|
1.0000
|
|
0.30
|
1.0000
|
|
0.35
|
0.9889
|
|
0.40
|
0.9778
|
|
0.45
|
0.9556
|
|
0.50
|
0.9333
|
|
0.55
|
0.8889
|
|
0.60
|
0.8444
|
|
0.65
|
0.8000
|
|
0.70
|
0.7556
|
|
0.75
|
0.7000
|
|
0.80
|
0.6333
|
|
0.85
|
0.5560
|
|
0.90
|
0.4444
|
|
0.95
|
0.3333
|
|
1.00
|
0.0000
|
See Also