Session: 05-03: Applied CFD

Paper Number: 131459

131459 - Systematic Development of Modification Functions for Improved Rans Turbulence Model Performance in Free Shear Flows 

This paper presents a methodology for the development of modification functions to Reynolds-Averaged Navier Stokes (RANS) turbulence models. The specific model investigated in this paper is the k-w SST turbulence model. The k-w SST turbulence model has been used widely since its introduction and is today an industry standard for applied CFD. It is therefore considered an ideal model for the demonstration of the methodology proposed here. Modification functions are developed and applied to improve the accuracy of the model in self-similar free shear flows. This initial demonstration focuses on five canonical incompressible free shear flows: plane jet, axisymmetric jet, plane wake, axisymmetric wake, and plane mixing layer. Several previous studies have investigated modifying the k-w model to improve its accuracy. Some of these corrections are applied for specific cases, and as such lose the generality of the k-w model. The goal of this paper is to correct the k-w model for a wide range of flows and cases in order to retain the generality of the underlying k-w model. The approach used here is based on the adoption of specific functional forms for coefficients in specific model terms, followed by optimization of the constants in the modification functions. The independent variables in the modification functions are local dimensionless quantities allowing straightforward implementation into existing RANS-based CFD solvers. Modification functions are initially investigated for the turbulent viscosity, the destruction term in the turbulent kinetic energy (k) equation, and the production and destruction terms in the specific turbulent dissipation rate (w) equation. Results show that the method can successfully yield improved model performance over the entire range of test cases investigated.

This paper presents a methodology for the development of modification functions to Reynolds-Averaged Navier Stokes (RANS) turbulence models. The specific model investigated in this paper is the k-w SST turbulence model. The k-w SST turbulence model has been used widely since its introduction and is today an industry standard for applied CFD. It is therefore considered an ideal model for the demonstration of the methodology proposed here. Modification functions are developed and applied to improve the accuracy of the model in self-similar free shear flows. This initial demonstration focuses on five canonical incompressible free shear flows: plane jet, axisymmetric jet, plane wake, axisymmetric wake, and plane mixing layer. Several previous studies have investigated modifying the k-w model to improve its accuracy. Some of these corrections are applied for specific cases, and as such lose the generality of the k-w model. The goal of this paper is to correct the k-w model for a wide range of flows and cases in order to retain the generality of the underlying k-w model. The approach used here is based on the adoption of specific functional forms for coefficients in specific model terms, followed by optimization of the constants in the modification functions. The independent variables in the modification functions are local dimensionless quantities allowing straightforward implementation into existing RANS-based CFD solvers. Modification functions are initially investigated for the turbulent viscosity, the destruction term in the turbulent kinetic energy (k) equation, and the production and destruction terms in the specific turbulent dissipation rate (w) equation. Results show that the method can successfully yield improved model performance over the entire range of test cases investigated.

Presenting Author: Michael Tullis University of Arkansas