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Spalart-Allmaras model in Ansys Fluent 12.0 theory guide

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Old   February 7, 2010, 18:03
Default Spalart-Allmaras model in Ansys Fluent 12.0 theory guide
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François Grégoire
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From Theory guide, chapter 4:

4.3.7 Wall Boundary Conditions

When the mesh is fine enough to resolve the viscosity-dominated sublayer, the wall shear stress is obtained from the laminar stress-strain relationship: (4.3-16)

If the mesh is too coarse to resolve the viscous sublayer, then it is assumed that the centroid of the wall-adjacent cell falls within the logarithmic region of the boundary layer, and the law-of-the-wall is employed: (4.3-17)

At what y+ Fluent does the switch??? It's not clear here. Is it at y+>11.225 as explained for Standard Wall Functions in section 4.12.2 of Theory guide?

Thanks in advance,
Cheers.



From Theory guide, chapter 12:

12.13.8 Low-Re Damping
If either of the Spalart-Allmaras or the Spalart-Allmaras Detached Eddy Simulation models are used, you may enable a low-Reynolds damping to the turbulent viscosity by enabling the Low-Re Damping option under Spalart-Allmaras Options in the Viscous Model dialog box.

This only tells me that I can activate Low-Re damping by activating Low-Re damping... Does anyone know what consequence has this Low-Re damping?
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