Evaluation of the Near-Wall k-Epsilon Turbulence Model by Comparison with Direct Simulations of Turbulent Channel Flow.

摘要

Results have been reported for the direct numerical simulation (DNS) of a turbulent channel flow at moderate Reynolds number. These data are used to evaluate the terms in the exact and modeled transport equations for the turbulence kinetic energy, k, and the isotropic dissipation function, epsilon. Both transport equations show significant imbalances in the sums of the modeled terms in the high shear region near the channel walls. The model for the eddy viscosity is found to yield distributions for the modeled shear and production terms which do not agree well with the distributions calculated from the DNS data. The source of the imbalance is attributed to the wall damping function, f sub mu, which is required in eddy viscosity models for turbulent flows near walls. Several models for f sub mu are examined, and it is found that the models do not vary across the channel as does f sub mu when evaluated from the DNS data. The Lam-Bremhorst model is found to give reasonable agreement with the DNS data. The standard van Driest model is found to give better agreement with the DNS data. Modification of the van Driest model to include an effective origin improves agreement and gives very good agreement between the modeled shear and the shear calculated from the DNS data. Keywords: Turbulence modeling; Low reynolds number turbulence; Wall damping; Two equation models; Direct simulation data.