Recent advances in numerical simulation of 3D unsteady convection controlled by buoyancy and rotation
Various approaches to generate 3D unsteady numerical solutions for non-isothermal turbulent flows under action of buoyancy and/or rotation are discussed. Well-known techniques are Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES). With reference to applications of the LES technique in problems of engineering interest, a special attention is paid to near-wall-layer models dealing with coarse or moderate grids. A recently developed technique based on a hybridisation of Reynolds-Averaged Navier-Stokes models with LES (RANS/LES) is described. Results of examination of LES and RANS/LES capabilities as compared with known high-accuracy DNS data for turbulent Rayleigh-Benard convection in a rotating horizontal layer are discussed. A promising experience of application of RANS/LES technique to strongly turbulent thermal convection of mercury in a cylindrical cell is presented. Recent achievements in LES and RANS/LES of molten silicon turbulent convection in real-geometry rotating crucibles of Czochralski (CZ) systems for single-crystal growth are reviewed. Attention is paid to capabilities of these numerical techniques to predict baroclinic instabilities at the melt periphery and high-intensity fluctuations in the under-crystal region, playing a primary role in formation of macroscopic inhomogeneities of the growing crystal. Results of DNS studies of 3D unsteady mixed convection developing in a rapidly rotating annular cavity are described in comparison with known experimental data for a simplified model of configurations typical for axial compressors of high-temperature gas turbines.