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9.3. Advice on use of low-Re models

Since low-Reynolds-number modelling requires that the equations be integrated right down to the wall, care must be taken to ensure good numerical resolution in the near-wall region. For advice and information on selecting a suitable grid size and distribution, the user is referred to: -

(a) the documentation provided under Section 3.4.4 above for the LAM-Bremhorst KE-EP turbulence model; and

(b) the Q1 examples provided in the Advanced-Turbulence-models library.

The two-layer model is recommended in preference to the Lam- Bremhorst model, mainly on the grounds that it requires less numerical resolution in the near-wall layer, and that it provides a better length scale in these regions. This latter point is particularly important in turbulent heat transfer problems involving separation.

The KE-OMEG model has some advantages in transitional applications and in flows with adverse pressure gradients. The model appears to be very convergent, and might be considered if convergence is proving difficult with other low-Re models. For further information, the reader is referred to Section 3.4.6 above.