Simulation and analysis of transcritical turbulent boundary layers with heat transfer

Transcritical CO2 plays an important role in the development of energy technologies. As CO2 transitions between subcritical and supercritical states, it experiences a pseudo phase change in which density and transport properties undergo rapid changes for small corresponding changes in temperature. The location of the pseudo phase change in turbulent, wall-bounded flows imposes an extra length scale that affects the scaling of turbulence statistics. This work uses a set of high-resolution numerical simulations of zero-pressure-gradient turbulent boundary layer flows to study the effects of near-wall pseudo phase changes on the turbulence dynamics. Simulations are conducted using compact finite difference methods, and no solution filtering or artificial numerical dissipation is needed for robustness. The simulations are configured at several supercritical pressures and different wall temperatures. In addition, the freestream and wall temperatures stride the critical condition at which the pseudo phase change occurs. The turbulence statistics are investigated to characterize the effects of abrupt changes in the transport properties and density of the transcritical fluid on the behavior of wall-bounded turbulence. Transformation and scaling analyses proposed in the literature for supersonic boundary layers are also evaluated.