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Abstract High-pressure transcritical wall-bounded flows exhibit strong coupling between hydrodynamic and thermodynamic fluctuations, particularly near the pseudoboiling region where large density gradients arise. Understanding the coherent motions that emerge in this regime remains essential for advancing reduced-order modeling strategies at high pressures. In this work, first observations of coherent structures in a transcritical turbulent channel flow using data-driven analysis tools are presented. Using a low-Mach-number DNS database, preliminary modal investigations show streamwise-elongated fluctuations interacting with near-wall pseudo-boiling layers. Spectral analysis using Fast Fourier Transform reveals energetic low-frequency dynamics associated with density–temperature coupling. In addition, percolation-based segmentation is employed to detect spatial intermittency, uncovering localized thermodynamic activity clusters that align with regions of amplified response. Initial data-driven reconstructions highlight limitations in modal collapse, suggesting that real-fluid effects introduce strong spatial–temporal variability that challenges classical low-order descriptions. These findings provide early structural insight into energy-containing motions in transcritical wall turbulence and lay the groundwork for future integration with resolvent analysis and hybrid reduced-order modeling.
Bernades et al. (Fri,) studied this question.