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

1.采用三维时变有限差分格式对水平同心环空内的湍流自然对流进行了直接数值模拟。给出了缝隙宽度从1.0×10~(^6)到1.72×10~(^7)的瑞利数的数值结果。为了验证该格式的有效性，将统计处理的数值结果与空气或液态金属的实验数据和数值解进行了比较，并研究了网格尺寸对空间分辨率的影响。结果表明，由适当的空间分辨率推导出的时间平均量与实验结果吻合较好，而当空间分辨率不足时，湍流量被过度估计。对水平同心环空中的湍流自然对流进行了大涡模拟。给出了宽度为2.51×10~(^6)~1.18×10~(^9)的瑞利数的数值结果。为了验证数值模拟的有效性，数值结果与其他实验数据进行了比较。结果表明，LES对湍流自然习性的预测是有效的。

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.