Clipping over dissipation in turbulence models

TL;DR

This paper investigates two phenomenological clipping strategies in turbulence models to prevent over dissipation caused by eddy viscosity, analyzing their effectiveness in shear flow and periodic turbulence scenarios.

Contribution

It introduces and analyzes two clipping methods for turbulence models, demonstrating their effectiveness in reducing over dissipation in different flow conditions.

Findings

Both clipping strategies prevent over dissipation in turbulence models.

Clipping the turbulent viscosity aligns near-wall behavior with true Reynolds stresses.

Clipping the turbulence length scale reduces excessive interior flow dissipation.

Abstract

Clipping refers to adding 1 line of code A=min{A,B} to force the variable A to stay below a present bound B. Phenomenological clipping also occurs in turbulence models to correct for over dissipation caused by the action of eddy viscosity terms in regions of small scales. Herein we analyze eddy viscosity model energy dissipation rates with 2 phenomenological clipping strategies. Since the true Reynolds stresses are O(d^2) (d= wall normal distance) in the near wall region, the first is to force this near wall behavior in the eddy viscosity by clipping the turbulent viscosity. The second is Escudier's early proposal to clip the turbulence length scale, reducing too large values in the interior of the flow. Analyzing respectively shear flow turbulence and turbulence in a box (i.e., periodic boundary conditions), we show that both clipping strategies do prevent aggregate over dissipation of model solutions.