We present recent results from large eddy simulations (LES) of bounded, turbulent, double-diffusive convection in seawater, focusing on small-aspect-ratio domains (2:2:1) across an extensive parameter range. We focus on presenting the main instantaneous and time-averaged features of flow, heat, and concentration fields. In addition to analyzing the power spectral density (PSD) and probability density function (PDF) at characteristic locations within the simulated domain, special attention is devoted to a detailed analysis of the budgets of the governing second-order correlations for different strengths of the imposed stable thermal stratification gradient.

The present study addresses numerical simulations of the double-diffusive convection in a turbulent regime. The characteristic concentration and temperature Prandtl numbers (PrC = 700 and PrT = 7) correspond to the typical seawater properties. Here, we applied the Large-Eddy Simulation (LES) approach, with relatively simple subgrid turbulence closures of momentum, concentration, and temperature for the unresolved scales. The wall-resolved LES approach proved to work well on significantly coarser numerical mesh than used in recent Direct Numerical Simulation (DNS) studies of Yang et al. (2016) in the intermediate range of working parameters, 107 ≤ RaC ≤ 109, 0 ≤ RaT ≤ 106, which covers the quasi-Rayleigh-Bénard, fingering, and damping flow regimes. A good agreement between concentration and temperature Nusselt numbers is obtained. The instantaneous Nusselt numbers distribution revealed a significant impact of the imposed strong thermal stratification (RaT = 106) in comparison to the neutral case (RaT = 0).