A New Scalar Reynolds Stress Model For Non-Isothermal Wall Bounded Turbulent Flows

The present investigation concerns the development of advanced scalar turbulence modeling approaches and their application to the calculation of non-isothermal wall-bounded flow phenomena. A new scalar modeling technique based on scalar turbulent scales is proposed and implemented at a second-order modeling approach. Instead of the classical analogy concept between the mechanical and the scalar transport mechanisms, a scalar time scale, defined as the ratio of the temperature variance and its rate of dissipation or scalar dissipation rate, is used to tackle the scalar turbulence closure problem. A simple scalar Reynolds stress model, capable of predicting various heat transport problems, is developed and tested by comparing its results for a thermal boundary layer with its standard mechanical counterpart as well as first-order models like the k-ε model and the g-χ model, a scalar version of the standard k-ε model. Validation against experimental data is performed and shows clearly the benefits of adopting the right scales for the right phenomenon: mechanical scales for momentum transport and specific scalar scales for scalar transport. Key-Words: Turbulence Scales, Turbulence Models, Thermal Boundary Layer, Turbulent Prandtl Number.