Heat transfer scaling regimes and associated transport mechanisms in vertical convection

This Letter revisits heat transfer scaling (Nu∼Ram) and the associated transport mechanism in vertical convection over a wide Rayleigh number 106≤Ra≤3×1012. Three regimes emerge in the Nu∼Ram scaling (Nu is the Nusselt number): laminar (106≤Ra≤109;m=0.251); weak-turbulent (109≤Ra<1011;m=0.28); and turbulent (1011≤Ra<3×1012;m=0.325). The transition to turbulence occurs at lower Ra(≈109) than in Wang et al. [“Regime transitions in thermally driven high-Rayleigh number vertical convection,” J. Fluid Mech. 917, A6 (2021)], due to enhanced plume ejection from extended plates. Heat transport shifts from sidewall-driven stratification to chaotic plume mixing, with vertical velocity scaling changing from Ra−0.5 to Ra0.25 in the three regimes, which is confirmed from −5/3 scaling-law in Energy spectrum.