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首页> 外文期刊>International Journal of Heat and Mass Transfer >DNS of turbulent thermal boundary layers up to Re_θ = 2300
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DNS of turbulent thermal boundary layers up to Re_θ = 2300

机译：高达Re_θ= 2300的湍流热边界层的DNS

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摘要

A technique, based on the Lund et al. (1998) [1] approach, is introduced in order to numerically prescribe time-dependent turbulent inflow conditions in spatially-developing thermal boundary layers. A major difference with Lund's approach is that the new multi-scale approach considers different scaling laws for the inner and outer parts of the boundary layer. Direct numerical simulations (DNS) are performed for incompressible zero (ZPG) and adverse (APG) pressure gradient flows. To the best of our knowledge, the present DNS in ZPG flows at a momentum thickness Reynolds numbers (Re_θ) of 2300 represents the evolving thermal boundary layer simulations at the highest Re_θ in the turbulence community. The temperature is treated as a passive scalar with isothermal walls as a boundary condition and a molecular Pra-ndtl number of 0.71. The predicted Stanton number shows fairly good agreement with empirical correlations, and experimental and numerical data from the literature. Moreover, the influences of the Reynolds number and the APG strength on thermal parameters are also examined. Furthermore, the budget of the temperature variance shows a significant increase of production, turbulent diffusion, and dissipation in the buffer layer at higher Reynolds numbers. The main effects of adverse pressure gradients on the temperature field are manifested by a decreasing trend of thermal fluctuations but an increasing trend of the wall-normal turbulent heat fluxes when normalized by wall units as the APG strength is augmented.
机译：一种基于Lund等人的技术。 （1998）[1]方法被引入，以便在空间发展的热边界层中以数值方式规定与时间有关的湍流流入条件。 Lund方法的主要区别在于，新的多尺度方法对边界层的内部和外部部分考虑了不同的缩放定律。对不可压缩零（ZPG）和逆向（APG）压力梯度流执行直接数值模拟（DNS）。据我们所知，当前ZPG中的DNS以2300的动量厚度雷诺数（Re_θ）流动，代表了湍流界中最高Re_θ处不断发展的热边界层模拟。该温度被视为被动标量，以等温壁为边界条件，分子Prandtl值为0.71。预测的Stanton数与经验相关性以及来自文献的实验和数值数据非常吻合。此外，还研究了雷诺数和APG强度对热参数的影响。此外，温度变化的预算表明，在较高的雷诺数下，缓冲层中的产量，湍流扩散和耗散量显着增加。逆压力梯度对温度场的主要影响表现为热波动的减小趋势，但当壁厚单位归一化时，随着APG强度的增加，壁面法向湍流热通量呈上升趋势。

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