Parallel Stormwater Branch Modeling

[Evan5]

I need to cut an 18" pipe...have it dump into a concrete box with three 10" pipes for outlets. I'm not sure how to model the flows to see if the 10" pipes will cause headwater problems.
Thanks in advance.

 

[Evan5]

BTW, I have all the flow characteristics of the 18" pipe.

 

[tsgrue]

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SWMM will handle this, but I am not sure if you are asking about a software application for the modeling, the specific methodology to apply, or something else...

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tsgrue: site engineering, stormwater
management, landscape design, ecosystem
rehabilitation, mathematical simulation

http://hhwq.blogspot.com

 

[Evan5]

I used the 18" pipe outflow & checked the max flow of the smaller pipes using Manning's Eq.

Then I divided the 18" design flow by the max small pipe flow....say 10cfs/3cfs = 3.33cfs ....so I'll use four of the small pipes, neglecting minor losses.

Using four pipes gives a max flow of 4 x 3 = 12cfs & 10/12 = 16% increase in flow capacity.

Thanks for your input.
~E

 

[gbam]

Your approach is a good starting point, now you need to evaluate the headloss in your junction box. Provided all parameters are the same for your multi-cell outfall pipe, you can use the parameters for one 10" and determine the headloss to the box. Use the resulting HGL to evaluate the impact on the 18". Many of the software programs today will model the 4-10" pipes as outfall as tsgrue mentioned above.