Heat Transfer in Wall-bounded Flows at Transcritical Conditions

Despite the prevalence of fluids at transcritical conditions in engineering applications, the structure of the thermo-viscous boundary layer and heat transfer in wall-bounded flows are only incompletely understood. To address this, DNS of a channel flow at transcritical conditions is performed, in which a temperature differential at the bottom and top walls is prescribed so that the thermodynamic state of the fluid crosses the Widom line and the density varies by a factor of 18. The DNS is analyzed with the specific focus on examining the thermo-viscous boundary layer structure and testing the scaling relations. It is found that the canonical van Driest transformation performs well in describing the logarithmic wall layer region, and the observed scaling behavior of the streamwise energy spectrum provides support of the attached-eddy model at transcritical conditions.