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arXiv 0707.2485physics.flu-dyn
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Rayleigh-Benard对流中边界层的谱分析

Spectral analysis of boundary layers in Rayleigh-Benard convection

Jos Verdoold, Maarten van Reeuwijk, Mark J. Tummers, Harm J. J. Jonker, Kemo Hanjalić

备注：
10 pages, 6 figures, Accepted for publication in Phys. Rev. E
发表信息：
Phys. Rev. E 77, 016303 2008
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摘要：

为了更好地了解边界层的特性，对纵横比为4：1的Rayleigh-Bénard单元中的边界层进行了实验和数值研究。实验涉及的同时激光多普勒风速仪（LDA）测量的流体速度在两个位置，即在边界层和远离它的散装，瑞利数之间变化的$1.6 \times 10^7$和$2.4 \times 10^9$。在并行，直接数值模拟（DNS）已进行相同的配置之间的$7.0 \times 10^4$和$7.7 \times 10^7$的瑞利数。在边界层和大体积流中测得的温度和速度概率密度函数和水平速度波动的功率谱被发现实际上是相同的。除最小瑞利数外，边界层和体中心区的谱是连续的，并有很宽的活动尺度范围。这表明，在所考虑的$\textrm{Ra}$数范围内，体层和边界层都是紊流。然而，仍然可以观察到分子效应，并且边界层的行为不像经典的剪切驱动的湍流边界层。

英文摘要：

A combined experimental and numerical study of the boundary layer in a 4:1 aspect-ratio Rayleigh-Bénard cell over a four-decade range of Rayleigh numbers has been undertaken aimed at gaining a better insight into the character of the boundary layers. The experiments involved the simultaneous Laser Doppler Anemometry (LDA) measurements of fluid velocity at two locations, i.e. in the boundary layer and far away from it in the bulk, for Rayleigh numbers varying between $1.6 \times 10^7$ and $2.4 \times 10^9$. In parallel, direct numerical simulations (DNS) have been performed for the same configuration for Rayleigh numbers between $7.0 \times 10^4$ and $7.7 \times 10^7$. The temperature and velocity probability density functions and the power spectra of the horizontal velocity fluctuations measured in the boundary layer and in the bulk flow are found to be practically identical. Except for the smallest Rayleigh numbers, the spectra in the boundary layer and in the bulk central region are continuous and have a wide range of active scales. This indicates that both the bulk and the boundary layers are turbulent in the $\textrm{Ra}$ number range considered. However, molecular effects can still be observed and the boundary layer does not behave like a classical shear-driven turbulent boundary layer.

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