78th Annual Meeting of the APS Division of Fluid Dynamics (Nov 23 — 25, 2025)
P042: Sunrise over sCO2
Supercritical carbon dioxide (sCO2) undergoes large changes in density for small corresponding changes in temperature near the critical point. It is thus used as an alternative working fluid to make power cycles more compact and efficient. This visualization sheds light on two simulations of external flows utilizing the Peng-Robinson equation of state (EOS) to capture the thermodynamic complexities of sCO2. The bottom image is a DNS of a compressible turbulent boundary layer (CTBL) with Reτ = 250-400, and the top image is an LES of flow over a cylinder at Re = 3900. The former is run with a cooled wall and hot freestream straddling the critical point while the latter is run under ideal gas conditions at a supercritical temperature with the same EOS models. The CTBL visualization is taken in the streamwise-spanwise plane at a y+-value of approximately 25. The cylinder visualization is taken in a plane orthogonal to the spanwise direction. The light and dark contours represent regions of high and low density respectively for both visualizations, and for the CTBL, differ by more than a factor of three for corresponding temperature ratios close to one. With this setup, we now wonder: what would density contours in a fully transcritical cylinder flow look like, and how would these conditions impact heat transfer?
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