In this study, a series of scale-resolving numerical simulations of mixed convection at a Richardson number of $\text{Ri}=1$ for heavy liquid metals is conducted to investigate the flow organization. The large-scale longitudinal rollers produced by the combination of shear and buoyancy effects are observed in mixed convection, and they occupy the whole channel height. Turbulence coherence and transportation are enhanced by longitudinal rollers, which are quantitatively supported by two-point spatial autocorrelations and quadrant analysis. Thermal stripes are captured, revealing the footprints of longitudinal rollers at wall vicinity. The multiscale characteristic of flow structures at wall vicinity is resolved. The velocity patches and streaks inside patches correspond to large- and small-scale motions, respectively, which are quantitatively identified by the typical separation wavelength ${\lambda }_z^{+}\approx 1000$. Mean velocity and temperature profiles are well predicted by the Businger-Dyer relationship with exponent $-1$ based on Monin-Obukhov similarity theory. As well, the phenomenological logarithmic behavior with slope modulation of mean velocity is observed. We utilize the linear coherence spectrum and an improved wall-attached eddy model to give an intuitive physical interpretation of this phenomenon. The equivalence between slope modulation coefficient and fraction of space occupied by wall-attached eddy structures is established, and it has been further scrutinized under several extended operating conditions.

Close

PrevNext

View figure in article

• Shear layer turbulence
• Stratified turbulence
• Turbulence modeling
• Turbulence simulations
• Turbulent mixing