HEC RAS warning msg: subcritical analysis, while trying to calculate culvert and weir flow

[gsharif]

Hi Guys,

I am new to HEC RAS and modelling a small stream about 7 km in length, but at one of the culvert section it is giving me this warning msg and I can see from the culvert output the weir flow and flow inside the culvert is not matching up with the flow. The flow should be 9.15 m3/s but weir flow itself showing more than 400 m3/s. I have attached the profile output and up/down stream cross section. For information, I was using a long cross section at the upstream as there is a huge farmers field and I was trying to see how long the water will go. Should I use the water level and ignore this warning msg? Or need to fix this problem? any suggestion? Thanks.

GS

 

[gsharif]

I just realize the picture didnt get uploaded! The warnings are:

1. During subcritical analysis, while trying to calculate culvert and weir flow, the program could not get a balance of energy within the specified tolerance and number of trials. The program used the solution with the minimum error.
2. During the culvert inlet control computations, the program could not balance the culvert/weir flow. The reported inlet energy grade answer may not be valid.

 

[cvg]

perhaps mixed flow analysis would work better

 

[SMIAH]

What are your downstream/upstream boundary conditions.
What are your steady/unsteady flow condition.

 

[gsharif]

Hi, I am using steady flow of 9.15 m3/s for both upstream and downstream cross section. The boundary condition is - critical depth (downstream) but I have used normal depth (downstream) and both are giving me same problem!

 

[SMIAH]

You can upload your file?