SimScale CAE Forum

Correct boundary condition settings for a turbulent wall resolved mesh


#1

Hello community,

i need some knowledge for a turbulent incompressible case.

turbulence modells:

  • kEpsilon
  • kOmega

Could any body write down the correct boundary condition for a turbulent wall resolved mesh.

patch wall:

  • U: noSlip
  • p: zeroGradient
  • k: zeroGradient or fixedValue 0 ?
  • omega?
  • epsilon?
  • nut = calculated?

#2

Hi @e0625598!

Please refer to this post: Defining Turbulent Boundary Conditions

Also the names you states for the “wall patch” you have to make a difference between the patch and the actual wall boundary condition:

  • Patch: Generic type containing no geometric or topological information about the mesh (inlet, outlet, etc.)
  • Wall: Rigid Wall (patch that coincides with a solid wall \rightarrow using wall functions)

The names are identical on the platform. What case are you trying to simulate? Did you already have a look at the Public Project section to look for a template?

Cheers,

Jousef


#3

Hello @jousefm,
thanks you for your link, but i could not find the required information.

What setting the solver is using when Full resolution on wall boundary condition is selected.

what setting are set on the backend for:

  • U
  • p
  • k
  • nut
  • omega (if kOmegaSST turbulence model is used)
  • epsilon (if kEpsilon turbulence model is used)

Thank you in advance


#4

Hi @e0625598!

This post might help you out about yplus and wall functions in general: What is y+ (yplus)?


  1. “Full boundary layer Resolution”
  • yPlus around 1 (in the viscous sublayer)

  • current setup: k = 0

  • omega = omegaWallFunction

  • nut = nutkWallFunction*


  1. “Wall function approach”
  • 30 < yPlus < 300 (in the logarithmic sublayer)

  • Current setup: k = kqRWallFunction

  • omega = omegaWallFunction

  • epsilon = epsilonWallFunction

  • nut = nutkWallFunction


Does that help? For further information I would need to delve a bit deeper into it and see what I can find out.

Cheers,

Jousef


#5

@e0625598 you can find the backend definitions by downloading the solved case file and reading the patch definitions for each variable in time 0.

Best,
Darren