Department of Physics, University of California, Santa Barbara, California 93106, USA.
Phys Rev Lett. 2012 Feb 3;108(5):054501. doi: 10.1103/PhysRevLett.108.054501. Epub 2012 Feb 1.
Using compressed gases with Prandtl numbers near 0.7, we obtained flow visualizations of turbulent Rayleigh-Bénard convection in a cylindrical sample with an aspect ratio Γ≡D/L≅10 (D is the diameter and L the height) by the shadowgraph method. Focusing on the plumes under the top plate, we found that their length had a log-normal distribution, suggesting a fragmentation process. Fragmentation events could be visually identified in the images and involved plume interactions with bulk fluctuations or upwelling domain walls. We found the mean spacing between plumes to vary with the Rayleigh number in proportion to the volume-averaged Kolmogorov length of the turbulent bulk fluctuations, providing further evidence for plume-bulk interactions.
使用普朗特数接近 0.7 的压缩气体，我们通过阴影法获得了圆柱样品中湍流传热瑞利-贝纳德对流的流动可视化，该圆柱样品的纵横比 Γ≡D/L≅10（D 是直径，L 是高度）。我们专注于顶板下的羽流，发现它们的长度呈对数正态分布，表明存在碎裂过程。在图像中可以直观地识别出碎裂事件，涉及羽流与体脉动或上升域壁的相互作用。我们发现羽流之间的平均间距与瑞利数成正比，与湍流产体的平均 Kolmogorov 长度成比例，这为羽流-体相互作用提供了进一步的证据。
