I am trying to troubleshoot some steady state bridge models that may have bad geometry and need some finetuning with parameter adjustments. I read the blog post on troubleshooting culverts/bridges and interested if anyone had any additional information on using the internal boundary at the bridge with the Htab curves.
I know from the help menu documentation it says that it uses these curves to facilitate unsteady flow simulations. I was interested in using these to rapidly assess sensitivity of my bridge models to adjustments of parameters such as roughness, effective flow, changes in Q, ect, and look for situations where the model is having problems. However, I guess I am looking for more documentation on how exactly HEC is calculating these curves so I can better apply it to my steady state problems.
Specifically,
1. What exactly is the free flow curve… is it just the steady state solution?
2. What XS are specifically the headwater and tailwater?
3. Do I need to rerun the geometric processor every time I make any adjustment to model geometry/parameters?
4. Any other considerations that I should take into account for this type of application?