Study on the generation mechanism and the delimitation of occurrence of counter gradient diffusion phenomenon in turbulent heat transfer

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In this study, the counter gradient diffusion phenomenon which often happens in the stably thermally stratified turbulent boundary layer and turbulent boundary layer with separation and reattachment, had been investigated by means of the direct numerical simulation (DNS), in which the rudimentary process of turbulence the counter gradient diffusion phenomenon appeared was observed and studied. Thermally stratified turbulent boundary layers under various weather and various turbulent heat transport phenomena in boundary layer with separation and reattachment were carried out via DNS, and the occurrence of the counter gradient diffusion phenomenon was successfully reproduced. Also, using the results of DNS, turbulence models in the large eddy simulation and Reynolds averaged Navier-Stokes equation simulation is evaluated in order to reconstruct technique of modelling of turbulence toward the establishment of the simulation of turbulent heat transfer in the next generation.