"A supercritical to subcritical transition is occurring during this time-step."

Hello Ahmed, 

Could you please confirm which solver are you using, is it dynamic solver - implicit / explicit within SewerGEMS / CivilStorm? 

The user notification implies that  a hydraulic jump may be occurring, which you might want to be aware of and conduits might be operating under pressure. It is information message at the moment unless you see any red flags in the model. 

If you could create a profile of that area and observe the flows through conduits that will help you to analyze the problem area and see if conduits are really flowing full i.e. operating under pressure. Check if you see flooding in the model elements at any time step. 

Hello Sushma,

It is  implicit within SewerGEMS, i want know why it is happened and how to avoid it.

Thanks,

Ahmed, this is an informational message that does not necessarily indicate a problem in the system. It is telling you that a hydraulic jump is occurring in the pipe. This may be a desirable condition in some cases, or it may be something you want to avoid based on your engineering judgement. 

You can read more about hydraulic jumps in the Help documentation, in our Stormwater book (starting on page 260), and an illustration can be seen in the following article (see the pipe between points "X" and "Y" in the profile screenshot, and see the section called "Rapidly Varied Flow (Hydraulic jumps)" - Hydraulic grade discontinuity at steep pipes or across nodes (frontwater analysis)

If you do not want t hydraulic jump in your pipe, you could attempt to make the slope of the pipe in question less steep if possible, to avoid an abrupt change from steep to flat.

Ahmed, this is an informational message that does not necessarily indicate a problem in the system. It is telling you that a hydraulic jump is occurring in the pipe. This may be a desirable condition in some cases, or it may be something you want to avoid based on your engineering judgement. 

You can read more about hydraulic jumps in the Help documentation, in our Stormwater book (starting on page 260), and an illustration can be seen in the following article (see the pipe between points "X" and "Y" in the profile screenshot, and see the section called "Rapidly Varied Flow (Hydraulic jumps)" - Hydraulic grade discontinuity at steep pipes or across nodes (frontwater analysis)

If you do not want t hydraulic jump in your pipe, you could attempt to make the slope of the pipe in question less steep if possible, to avoid an abrupt change from steep to flat.