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首页> 外文期刊>Journal of Fluid Mechanics >The large-scale footprint in small-scale Rayleigh-Benard turbulence
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The large-scale footprint in small-scale Rayleigh-Benard turbulence

机译：小规模的瑞利 - 奔奔湍流的大规模占地面积

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摘要

Turbulent convection systems are known to give rise to prominent large-scale circulation. At the same time, the 'background' (or 'small-scale') turbulence is also highly relevant and e.g. carries the majority of the heat transport in the bulk of the flow. Here, we investigate how the small-scale turbulence is interlinked with the large-scale flow organization of Rayleigh-Benard convection. Our results are based on a numerical simulation at Rayleigh number Ra = 10(8) in a large aspect ratio (Gamma = 32) cell to ensure a distinct scale separation. We extract local magnitudes and wavenumbers of small-scale turbulence and find significant correlation of large-scale variations in these quantities with the large-scale signal. Most notably, we find stronger temperature fluctuations and increased small-scale transport (by about 10% of the global Nusselt number Nu) in plume impacting regions and opposite trends in the plume emitting counterparts. This concerns wall distances up to 2 delta(theta) (thermal boundary layer thickness). Local wavenumbers are generally found to be higher on the plume emitting side compared to the impacting one. A second independent approach by means of conditional averages confirmed these findings and yields additional insight into the large-scale variation of small-scale properties. Our results have implications for the modelling of small-scale turbulence.
机译：众所周知，湍流对流系统会引起显著的大尺度环流。同时，“背景”（或“小尺度”）湍流也具有高度相关性，例如，在大部分气流中携带大部分热量传输。在这里，我们研究小尺度湍流是如何与瑞利-贝纳德对流的大尺度流动组织联系在一起的。我们的结果基于一个大纵横比（伽马=32）单元中瑞利数Ra=10（8）的数值模拟，以确保明显的尺度分离。我们提取了小尺度湍流的局部震级和波数，并发现这些量的大尺度变化与大尺度信号之间存在显著相关性。最值得注意的是，我们在羽流影响区域发现了更强的温度波动和增加的小规模输运（约占全球努塞尔数Nu的10%），而在羽流排放区域则发现了相反的趋势。这涉及到高达2δ（θ）的壁距（热边界层厚度）。通常发现，羽流发射侧的局部波数高于撞击侧。第二种通过条件平均值的独立方法证实了这些发现，并对小规模房地产的大规模变化产生了额外的见解。我们的结果对小尺度湍流的建模有启示。

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