Turbulent convection driven by surface cooling in shallow water

• Published in: Journal of fluid mechanics Vol. 464; pp. 81 - 111
• Main Authors: ZIKANOV, OLEG, SLINN, DONALD N., DHANAK, MANHAR R.
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 10.08.2002
• Subjects: Convection; Earth, ocean, space; Exact sciences and technology; External geophysics; Fluid mechanics; Other topics; Physics of the oceans; Shallow water; Simulation; Turbulence; Fluid mechanics; Cooling; Similarity; Reynolds number; Turbulent convection; Convective instability; Shallow water; Rayleigh Bénard instability; Numerical simulation; Turbulent fluctuation; Dynamic model; Performance; Richardson number; Heat transfer
• ISSN: 0022-1120; 1469-7645
• DOI: 10.1017/S0022112002001015

We present the results of large-eddy simulations (LES) of turbulent thermal convection generated by surface cooling in a finite-depth stably stratified horizontal layer with an isothermal bottom surface. The flow is a simplified model of turbulent convection occurring in the warm shallow ocean during adverse weather events. Simulations are performed in a 6 × 6 × 1 aspect ratio computational domain using the pseudo-spectral Fourier method in the horizontal plane and finite-difference discretization on a high-resolution clustered grid in the vertical direction. A moderate value of the Reynolds number and two different values of the Richardson number corresponding to a weak initial stratification are considered. A version of the dynamic model is applied as a subgrid-scale (SGS) closure. Its performance is evaluated based on comparison with the results of direct numerical simulations (DNS) and simulations using the Smagorinsky model. Comprehensive study of the spatial structure and statistical properties of the developed turbulent state shows some similarity to Rayleigh–Bénard convection and other types of turbulent thermal convection in horizontal layers, but also reveals distinctive features such as the dominance of a large-scale pattern of descending plumes and strong turbulent fluctuations near the surface.