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High Turbulent channel (duct) flow - a lot of problems

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Old   August 5, 2022, 13:04
Default High Turbulent channel (duct) flow - a lot of problems
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pao
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Hi guys! 1st post for me here at CFD-Online.
Great community , great people, thanks!


I'm currently trying to stabilize a simulation that doesn't want to "stay calm" -------- > EXPLOSION



I've a channel duct flow:
  • One inlet, air at 55 [m/s] (massflow = 1.5 [kg/s])
  • Reynolds at the inlet -> Re = 4.5e5
  • Two outlet where I'm imposing just the static pressure
  • Expected Reynolds at 1 of the 2 outlet -> Re= 8e5
  • At the inlet Ma<0.3 but in some inner regions of the domain it is reached and exceeded
  • So I'm using rhoSimpleFoam
  • kEpsilon with wall function
Are there some special BCs to impose to nut, T, p, U, etc. related to internal channel flow (compressible, very high turbulent) that I should use for this kind of problem?


Thanks
Pao
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Old   August 7, 2022, 04:39
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Santiago Lopez Castano
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Quote:
Originally Posted by pao View Post
[*]Expected Reynolds at 1 of the 2 outlet -> Re= 8e5
If you know the velocity at one of the two outlets, Why do you impose Neumann BC for velocity?
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Old   August 8, 2022, 03:08
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Hi,

Without additional information it's hard to say why your simulation crashes, so I can suggest some general things to check that might be the cause:

- Does it crash at the first few iterations or at a certain time?
- You could examine the log file, or monitor the residuals (https://doc.cfd.direct/openfoam/user...phs-monitoring) to find out which variable causes the problem (p,T,U etc.).
- Is your mesh fine? Are there any bad cells (use checkMesh)
- How did you calculate the BC for the turbulence model? You can estimate appropriate values e.g. at https://cfd-training.com/turbulent-b...ns-calculator/

Hope that helps, good luck!
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