New subgrid-scale models for large-eddy simulation of Rayleigh-Bénard convection

7th European Thermal-Sciences Conference

Dabbagh, F.^1 ; Trias, F.X.^1 ; Gorobets, A.^1,2 ; Oliva, A.^1

Heat and Mass Transfer Technological Center, Technical University of Catalonia, ETSEIAT, C/Colom 11, Terrassa

08222, Spain^1

Keldysh Institute of Applied Mathematics, 4A Miusskaya Sq., Moscow

125047, Russia^2

关键词: Approximate formulas;    Eddy Diffusivities;    Eddy viscosity model;    Independent values;    Sub-grid scale models;    Taylor series expansions;    Turbulent Prandtl number;    Turbulent Rayleigh-Benard convection;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/745/3/032041/pdf
DOI  :  10.1088/1742-6596/745/3/032041

来源: IOP

【 摘 要 】

At the crossroad between flow topology analysis and the theory of turbulence, a new eddy-viscosity model for Large-eddy simulation has been recently proposed by Trias et al.[PoF, 27, 065103 (2015)]. The S3PQR-model has the proper cubic near-wall behaviour and no intrinsic limitations for statistically inhomogeneous flows. In this work, the new model has been tested for an air turbulent Rayleigh-Benard convection in a rectangular cell of aspect ratio unity and n span-wise open-ended distance. To do so, direct numerical simulation has been carried out at two Rayleigh numbers Ra = 108and 1010, to assess the model performance and investigate a priori the effect of the turbulent Prandtl number. Using an approximate formula based on the Taylor series expansion, the turbulent Prandtl number has been calculated and revealed a constant and Ra-independent value across the bulk region equals to 0.55. It is found that the turbulent components of eddy-viscosity and eddy-diffusivity are positively prevalent to maintain a turbulent wind essentially driven by the mean buoyant force at the sidewalls. On the other hand, the new eddy-viscosity model is preliminary tested for the case of Ra = 108and showed overestimation of heat flux within the boundary layer but fairly good prediction of turbulent kinetics at this moderate turbulent flow.