Hydraulic Jump - StormCAD

Question

1- The pipe below (channel) in the model attached is showing Hydraulic Jump, can provide justification why that happened? and is there any enhancement to be done? 
 2- I have noticed that if the backwater analysis change to capacity analysis in the calculation option it will change the profile view, can please elaborate on that?

Regards, 
 Mohamad Azzam 
 Hydraulic Jump.7z

Jesse Dringoli · Accepted Answer

To add to Scott and Karl's responses - if the same hydraulic conditions occur when using the SWMM dynamic solver (ex: flow through the pipe at a particular timestep), I would still expect to see a transition from shallow supercritical flow to the higher tailwater condition, though the exact way that it appears in profile view may be slightly different. StormCAD and SewerCAD (GVF-Rational and GVF-Convex solvers) have a specific way of drawing a small arc to connect between the upstream and downstream water surface. 
 You would need to keep in mind that the SWMM solver is very different from the GVF solvers in other ways (with respect to methodologies and assumptions) and uses different data input for some elements, all of which can cause this to be an apples-to-oranges comparison. See more here . Though generally speaking as mentioned above, you should still see a transition from shallow to deeper depth. 
 Note that with the SWMM solver, results will be shown for the start, middle and stop side of the pipe, whereas with the Implicit solver, you can choose the "detailed" option for the "Output Options" dropdown in the conduit properties, and with a small enough Computation Distance (calculation option), you can see more detailed profile results. Here is an example: 
 Convex solver: 
 
 SWMM solver: 
 
 Implicit solver with detailed results turned on and 10 ft Computation Distance:

Scott Kampa · Answer

Hello Mohamad, 
 Hydraulic jumps are possible with a gradually varied flow calculation. It is most common with steep slopes, but there can be flow discontinuities that can occur in models based on this. The following link has some useful information: Hydraulic grade discontinuity at steep pipes or across nodes (frontwater analysis) . 
 Changing to Capacity Analysis can impact what the profile looks like. This link has more information on this: Backwater Analysis vs Capacity Analysis flow profile methods . 
 Regards, 
 Scott

Hydraulic Jump - StormCAD

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