Direct Numerical Simulation of Turbulent Thermal Diffusivity

The influence of the Reynolds and Prandtl numbers on the turbulent thermal diffusivity in a flat channel was studied. The data obtained by various research groups by direct numerical simulation were used. It was shown that the ratio of the turbulent thermal diffusivity to the molecular thermal diffusivity and to the Reynolds number calculated from the dynamic velocity is not a universal function of the dimensionless distance to the wall, as follows from the logarithmic formula for the temperature profile and the temperature defect law, but depends on the Reynolds and Prandtl numbers. Relationships were obtained that allow one to estimate this value at relatively large values of these parameters.