Direct numerical simulation of one-sided forced thermal convection in plane channels
Direct numerical simulation of one-sided forced thermal convection in plane channels
复制标题
平面通道中一侧强制热对流的直接数值模拟
DOI：
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发表时间：
2023
影响因子：
3.7
通讯作者：
D. Modesti
中科院分区：
文献类型：
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作者：
S. Pirozzoli;D. Modesti
本文对压力驱动的平面通道内的湍流流动和换热进行了直接数值模拟，考虑了两面加热和一面不对称加热的情况。摩擦雷诺数在2 0 0 0年左右，普朗特数从${Pr}=0.025$到${Pr}=4$，温度场被视为被动标量。在对称加热的情况下，温度场和流向速度场非常相似，湍流结构仅限于通道的一半，而在单侧加热的情况下，温度场显示出更大的区域，相干涨落延伸到通道中心线以外。证实了平均温度的对数定律的正确性，以及与之相关的von Kármán常数的普适性，我们估计该常数为$k{heta}=0.459$。在单面加热的情况下，与对数行为的偏差要明显得多，其特征是具有抛物线平均温度分布的较宽的外部区域。利用dns数据建立了换热系数随雷诺数和普朗特数变化的预测公式。我们发现，在单边情况下，在单位普朗特数下，热效率降低约为20美元，而在低普朗特数时，热效率的降低更为显著。
Abstract We carry out direct numerical simulations (DNS) of turbulent flow and heat transfer in pressure-driven plane channels, by considering cases with heating on both walls, as well as asymmetric heating limited to one of the channel walls. Friction Reynolds numbers up to ${Re}_{ au } approx 2000$ are considered, and Prandtl numbers from ${Pr}=0.025$ to ${Pr} = 4$, the temperature field being regarded as a passive scalar. Whereas cases with symmetric heating show close similarity between the temperature and the streamwise velocity fields, with turbulent structures confined to either half of the channel, in the presence of one-sided heating the temperature field exhibits larger regions with coherent fluctuations extending beyond the channel centreline. Validity of the logarithmic law for the mean temperature is confirmed, as well as universality of the associated von Kármán constant, which we estimate to be $k_{ heta } = 0.459$. Deviations from the logarithmic behaviour are much clearer in cases with one-sided heating, which feature a wide outer region with parabolic mean temperature profile. The DNS data are exploited to construct a predictive formula for the heat transfer coefficient as a function of both Reynolds and Prandtl number. We find that the reduction of the thermal efficiency in the one-sided case is approximately $20,\%$ at unit Prandtl number; however, it can become much more significant at low Prandtl number.