A critical evaluation of twoequation models for near wall turbulence
Abstract
A variety of twoequation turbulence models,including several versions of the Kepsilon model as well as the Komega model, are analyzed critically for near wall turbulent flows from a theoretical and computational standpoint. It is shown that the Kepsilon model has two major problems associated with it: the lack of natural boundary conditions for the dissipation rate and the appearance of higherorder correlations in the balance of terms for the dissipation rate at the wall. In so far as the former problem is concerned, either physically inconsistent boundary conditions have been used or the boundary conditions for the dissipation rate have been tied to higherorder derivatives of the turbulent kinetic energy which leads to numerical stiffness. The Komega model can alleviate these problems since the asymptotic behavior of omega is known in more detail and since its near wall balance involves only exact viscous terms. However, the modeled form of the omega equation that is used in the literature is incompletean exact viscous term is missing which causes the model to behave in an asymptotically inconsistent manner. By including this viscous term and by introducing new wall damping functions with improved asymptotic behavior, a new Ktau model (where tau is identical with 1/omega is turbulent time scale) is developed. It is demonstrated that this new model is computationally robust and yields improved predictions for turbulent boundary layers.
 Publication:

Final Report Institute for Computer Applications in Science and Engineering
 Pub Date:
 June 1990
 Bibcode:
 1990icas.reptU....S
 Keywords:

 Asymptotic Methods;
 Boundaries;
 Damping;
 KEpsilon Turbulence Model;
 Turbulence;
 Turbulent Boundary Layer;
 Wall Flow;
 Walls;
 Boundary Value Problems;
 Dissipation;
 Kinetic Energy;
 Stiffness;
 Turbulent Flow;
 Fluid Mechanics and Heat Transfer