Lateral culvert between two parallel reaches in HEC RAS
Lateral culvert between two parallel reaches in HEC RAS
(OP)
I am new to lateral structures. That said, I am trying to model a lateral culvert between two minor drainage channels linked by a culvert. The flow in the channels are not inter-related and the channel that is at the downstream end of the culvert has negligible flow (0.3 m3/s) compared to the channel upstream (3.9 m3/s). The culvert has a positive slope of about 4%. I have used steady state subcritical flow in the first run, and since the WS reached critical, tried the mixed flow. Problem is that in both cases I am getting a negative flow through the culvert ('Q leaving Total') for the lateral structure. The Total Q upstream and downstream of the lateral structure is same in the upstream side of the culvert, which is also incorrect. I also cannot find a report in HEC RAS that will throw some light on the culvert hydraulics (flow profile, inlet/outlet control, even if only for theoretical interest), though I have seen such report for inline culverts.
As an aside, what does the HW positioning (L overbank, Next to L bank etc.) of the weir mean in reality? THe HEC-RAS literature has not been much help (probably it's too simple?). My culverts are connected to the trapezoidal channels at the floor level of the channels where the side walls start to rise. I have the lateral weir positioned (HW Position in Lateral Structure Editor) at the Next to Bank. How would it affect the calculations if I were to position it next to overbank? Weir elevation is set to match the top of the side wall of the channel upstream, on the side that is facing the channel downstream.
Thanks!!
As an aside, what does the HW positioning (L overbank, Next to L bank etc.) of the weir mean in reality? THe HEC-RAS literature has not been much help (probably it's too simple?). My culverts are connected to the trapezoidal channels at the floor level of the channels where the side walls start to rise. I have the lateral weir positioned (HW Position in Lateral Structure Editor) at the Next to Bank. How would it affect the calculations if I were to position it next to overbank? Weir elevation is set to match the top of the side wall of the channel upstream, on the side that is facing the channel downstream.
Thanks!!





RE: Lateral culvert between two parallel reaches in HEC RAS
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RE: Lateral culvert between two parallel reaches in HEC RAS
RE: Lateral culvert between two parallel reaches in HEC RAS
RE: Lateral culvert between two parallel reaches in HEC RAS
RE: Lateral culvert between two parallel reaches in HEC RAS
The only other problem now is how to set a specific point on the reach downstream to tie the outlet of the culvert to. In the attached screenshot of the model, the wier seems to be connecting to two stations on the tailwater side of the culvert, but first - the culvert itself is not visible in the schematic. Is that normal?
Also strangely enough HEC-RAS doesn't report the velocity of the water through the culvert in the LAteral Structure Output table.
Attachment:
http://files.engineering.com/getfile.aspx?folder=7...