Anisotropy of Heat Transport and Its Modeling in Homogeneous Turbulent Flow

With modifications of a two-equation heat-transfer model, a new approach to analysis of heat transport in free turbulent shear flows is proposed. The modified model was tested by application to different homogeneous turbulent flows, namely decaying isotropic turbulence, homogeneous nonisotropic turbulence under a return-to-isotropy process, and homogeneous turbulence with a simple shear. To represent the nonisotropic nature of heat transfer in free turbulence, we have modeled the eddy diffusivity for heat by a second rank tensor on the basis of the generalized gradient diffusion hypothesis. At the same time, when treating the time scale which characterizes the transport process of a passive scalar, we have introduced the scalar-field time scale τθ=((θ2)^^-/2)/εθ. The predictions of turbulent heat flux, temperature variance and its dissipation rate are all in satisfactory agreement with the experimental results.