Validation of two- and three-equation wall-distance free turbulence models

A comparative study of low-Re wall-distance-free (WDF) turbulence models applied to incompressible flows is presented. The study includes the WDF k-ε and the three-equation WDF k-ε-γ as well as two k-ε models which involve the distance from the wall. Comparison with direct-numerical-simulation data reveals that the WDF models provide more accurate results for the dissipation rate, especially in the near wall region. A grid refinement study also reveals that models which explicitly involve the distance from the wall cannot capture the correct turbulence dissipation rate behaviour in the near-wall region even on the finest grid, where grid-independent solution is achieved. The low-Re WDF models require, however, increased number of iterations. Results are presented for channel and backward-facing step flows.