How can there be more flow in a pipe than its full capacity? #SWMM5 and #InfoSWMM
This post is borrowed from our Innovyze blog and modified for #SWMM5 http://blog.innovyze.com/2017/03/31/surcharge-flow-vs-pipe-full-capacity-in-icm/ You may have noticed, that in some instances, the Pipe full capacity value on a pipe in #SWMM5 is less than the maximum simulation flow in a surcharged pipe. How can there be more flow in a pipe than its full capacity? The Qfull in the link input summary table is calculated from the Manning's equation. Manning's equation is simpler than the full solution St Venant equations used by the SWMM5 simulation engine used to generate the model results. Therefore, there can sometimes be differences between Qfull (based on the slope) and the actual flow that can discharge as calculated using the 1D St Venant Equations. The Qfull value is only intended to be an approximation/reference for the user. It is not used by the engine to determine when a pipe goes into surcharge. Manning's equation assumes that the pipe is infinitely long and th...