Bug in steady flow boundary conditions?

Hec-Users,

I have run into a problem with the HEC-RAS v.2.2 steady flow boundary conditions.

I am running 4 profiles and have set the same known water surface at the downstream end of my river system for each proifile. The model runs successfully. BUT, instead of the water surface elevations converging to the same elevation, the water surface elevations remain different at the downstream end of the river.

Any ideas on what might be causing this problem?
Thanks,
Matthew P. Fischer
Taylor Engineering, Inc.

Check Fr # at downstream section. If known downstream water level is lower
than critical depth, Critical depth is reported (M2 profile).

Guillermo A. Regalado S.
G. Morris & Associates.
San Juan, PR

Matthew,

Perhaps the "known" water surface elevation you are setting at the downstream end is not realistic and the critical depth for each profile is calculated by the model instead. Try starting with normal or critical depth, depending on your downstream conditions.

Assuming you are modelling subcritical flow conditions, your model is not supposed to converge at the downstream end. It should converge somewhere upstream of your starting point if you have the same flow rate for each of the four profiles but a different starting elevation.

I hope this helps.
Frank Fisl
WaterCom Engineering