Stage-Storage: Pipe on a slope

[GleasonS]

I found a solution to a similar problem on an old thread but couldn't work the procedure to correctly solve my problem. Any help with the following problem would be greatly appreciated.

I have an underground pipe system that will be used for storage and would like to assemble a stage storage table to check the results of my computer modeled results (Hydraflow Hydrographs 2007). On an old thread, I found the following equation, however it doesn't yield results that one would expect (eg. the calculated full volume isn't what it should be)

http://www.eng-tips.com/viewthread.cfm?qid=12952&page=48

I also found this solution that, again, doesn't give me the results I would expect:

http://www.bossintl.com/forums/epa-swmm/13987-stage-storage-underground-pipe-slope.html

I have also looked up the procedure in HEC-22 with the same result. (This procedure is also duplicated in a number of state DOT hydrology manuals with minor variations)

To give some perspective, I am trying to assemble a stage storage table for an 12' long, 18" diameter pipe at a slope of 1.0%. It would seem that my max stage would be (assuming an starting invert of 100) 101.62. Like I said, I've tried modeling it a number of ways, and the max storage I was able to calculate was around 12cf not the 21cf one would expect.

Thanks

 

[gbam]

Here are results from a simple prog from FHWA (Visual Urban) which can be DL'd for free.
Stage(FT) Storage (CFT)
0 0
.2 1.0
.4 3.6
.6 6.9
.8 10.4
1.0 14.0
1.2 17.3
1.4 20.0
1.6 21.2

You can also set up a spreadsheet to compute the incremental stage-storage using properties of a partially full pipe and the average end area method to compute the vol.

Hope that helps.

 

[sharonporsche]

i second what gbam said; this should be pretty straight-forward to set up in a spreadsheet for a stage-storage calculation..

 

[GleasonS]

Thanks for the feedback, I haven't yet tried the average area method but will give it a shot.

I have my solutions setup in spreadsheets, however I think there was something wrong with how I was interpreting the variables. I was getting some pretty strange results (negative volumes, answers that DNE etc) so if anyone is familiar with the aforementioned methods and can provide some clarification that would also be helpful.

Thanks again.