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HHOS July 30, 2013 10:41

HelyxOS Boundary Conditions

I am using OpenFOAM v2.2.0 since a couple of weeks ago, and I am using HelyxOS to do the setting up of the case. The workflow is:
  1. Import a Fluent mesh into OpenFOAM
  2. Put some required dummy files in the case folder (maybe not so dummy, but yes as far as I know...)
  3. Load the case with HelyxOS.
  4. Set the whole case up.
  5. Change what I need to in files such as ControlDict.
  6. Run the case with OpenFoam from the terminal.

The problem is that I don't really understand all the Boundary Conditions options. I have been trying to find a document or so where they are explained, but I didn't find any...

Regarding the Velocity:
  • Fixed Value
  • Cylindrical Inlet Velocity
  • Surface normal Fixed value (why can't I put possitive values?)
  • Flow Rate Inlet
  • Pressure inlet Velocity
  • Pressure directed Inlet Velocity
  • Pressure inlet outlet Velocity
  • Pressure Directed Inlet Outlet Velocity
  • Freestream
  • Inlet Outlet Velocity
  • Zero gradient

I can roughly understand some, but all which I wrote in Bold letters, I have no idea. And what is the difference between Fixed Value and Freestream? The Zero gradient is not completely clear either.

Regarding the Pressure:
  • Fixed Value
  • Total Pressure
  • Freestream Pressure
  • Buoyant Pressure
  • Zero Gradient

Here I don't understand most of them... And if I want to set the atmospheric pressure in the boundaries, how can I do? Because I have to write a m^2/s^2 value...

It is a long and hard question, I guess... THANK YOU VERY MUCH FOR THE LITTLE HELP YOU MAY GIVE HERE :D

chegdan July 30, 2013 15:00

Hey There and welcome to the forum!

The best thing to do is look through the source code (especially the top of the .H files) for each BC and read the descriptions. If you have OpenFOAM correctly installed, you can go to


You might want to look over some slides I gave at the 8th OpenFOAM workshop located here. it is a basic training presentation on HELYX-OS. I am traveling today so I don't have time to answer your question in more depth.

Disclaimer: I work for the company that produces HELYX-OS

HHOS July 31, 2013 03:45

Thank you very much for the advice!

I have checked the .H files and, even if not in every case, they helped me to understand the boundary conditions a bit. I have also seen the PPT presentation; quite interesting. Anyway it would be nice to have some example where the BC can be usually applied; some seem very similar, but I know that the BC thing is very tricky... and I don't know if the results would change much; I guess that it may be so.

Again, thank you

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