Thermal boundary layers in turbulent Rayleigh–Bénard convection at aspect ratios between 1 and 9
Thermal boundary layers in turbulent Rayleigh–Bénard convection at aspect ratios between 1 and 9
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DOI：
10.1088/1367-2630/15/1/013040
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发表时间：
2013-01
影响因子：
3.3
通讯作者：
R. D. Puits;C. Resagk;A. Thess
中科院分区：
文献类型：
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作者：
R. D. Puits;C. Resagk;A. Thess
我们报告了在固定的普朗特数Pr = 0.7的空气中湍流瑞利-贝纳德对流的高分辨温度测量。扩展我们以前的工作（du Puits等人，2007年，J. Fluid Mech.572 231-54），我们在保持瑞利数恒定的同时，在各种纵横比下进行测量。我们表明，温度场内的对流边界层的两个水平板几乎是独立的全球流动模式伴随着纵横比的变化。由于实验设备的技术升级以及我们的温度测量的准确性和可靠性的显着提高，与我们以前的工作不同，我们发现，测量的时间平均温度场的轮廓既不遵循明确的幂律趋势，也不适合在边界层厚度的一个显着部分的线性或对数标度。分析在两个水平板处同时采集的温度数据，在改变纵横比Γ的同时观察到温度信号的互相关和自相关函数的各种转变。这些转变可能与总体流态从Γ = 1时的单滚流态向高展弦比时的双滚流态或多滚流态的变化有关。
We report highly resolved temperature measurements in turbulent Rayleigh–Bénard convection in air at a fixed Prandtl number Pr = 0.7. Extending our previous work (du Puits et al 2007 J. Fluid Mech. 572 231–54), we carried out measurements at various aspect ratios while keeping the Rayleigh number constant. We demonstrate that the temperature field inside the convective boundary layers of both horizontal plates is virtually independent on the global flow pattern accompanying the variation in the aspect ratio. Thanks to technical upgrades of the experimental facility as well as a significant improvement of the accuracy and reliability of our temperature measurement—and unlike in our previous work—we find that the measured profiles of the time-averaged temperature field neither follow a clear power-law trend nor fit a linear or a logarithmic scaling over a significant fraction of the boundary-layer thickness. Analyzing the temperature data simultaneously acquired at both horizontal plates, various transitions in the cross-correlation and the auto-correlation function of the temperature signals are observed while varying the aspect ratio Γ. These transitions might be associated with a change in the global flow pattern from a single-roll mode at Γ = 1 toward a double- or a multi-roll mode pattern at higher aspect ratios.