"Wave" forming on simulation startup
 

I am very new to Flow 3D and currently working on modeling flow over an ogee overflow weir as part of my capstone project. I have topography and bathymetry for my chosen site but first I modeled the geometry in a rectangular channel to see how things went. After some playing around I was able to get successful results and decided I would now work to import my contour data.

All my modeling has been done in AutoCAD or Civil 3D. I first took my contours (2D lines) and made a surface in Civil 3D which I then exported point data into a NEZ format and used the Topo2Stl addon in Flow 3D to create the STL file. Since I took the contours from Civil 3D but made my 3D solids of the dam/weir in AutoCAD, I ended up having to do some translations in Flow 3D to properly position the weir in the topography. This was a minor inconvenience and since it isn't for an actual project, I wasn't worried about any discrepancies in not positioning the structures in the exact location. I am only saying all this because I suspect the process I used might have something to do with my problem.

When I ran the simulation in the "box", I had no issues and the headwater/tailwater came in at the correct elevation and everything looked good, but for some reason, when I do the exact same simulation with the topo inserted, a huge wall of water comes flowing in from both the headpond and tailrace. I have looked through all my settings and can't for the life of me figure out what is going on. The especially odd thing is that if I switch the headwater and tailwater boundary conditions, the correct headwater level comes in at the tailwater and same thing with the tailwater level coming into the headpond.

I understand that to troubleshoot this issue you might need some log data or specific files but being new this software, I am not sure what those are so please just ask if there are additional files I should post.

Thank you
Bill

Any advice would be appreciated

It is hard to tell what the problem might be without looking at the input files and running the actual simulation. Can you please privately send me all the input files and I will try to take a look at them?

Did you procure the license through Flow Science's academic program? If yes, you know where to email directly. If not send it over on cfdonline itself.