Experimental Verification of Direct Numerical Simulation (DNS) of Turbulent Natural Convection in a Horizontal Annulus

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1. Direct numerical simulation using the three-dimensional and time-dependent finite difference scheme is performed for turbulent matural convection in a horizontal concentric annulus. Numerical results are obtained for the Rayleigh number based on the gap width from 1.0x10^6 to 1.72x10^7. To verify the validity of the present scheme, numerical results dealt with statistically are compared with experimental data using air or liquid metal and numerical solutions, and the effect of grid size on spatial resolution capability is investigated. It is shown that time averaged quantities deduced from appropriate spatial resolution are in good agreement with experimental results, whereas turbulence quantities are excessively estimated when spatial resolution is insufficient.2. LES (Large Eddy Simulation) is carried out for turbulent natural convection in a horizontal concentric annulus. Numerical results are obtained for the Rayleigh numbers based on the gap width for 2.51x10^6 to 1.18x10^9. To verify the validity of the simulation, numerical results are compared with other experimental data. LES proved to be valid for the prediction to turbulent natural convention.