论文标题
小型雷利 - 贝纳德湍流中的大规模占地面积
The large-scale footprint in small-scale Rayleigh-Bénard turbulence
论文作者
论文摘要
众所周知，湍流对流系统会引起显着的大规模循环。同时，“背景”（或“小规模”）的湍流也高度相关，例如在大部分流量中携带大部分热传输。在这里，我们研究了小规模的湍流如何与雷利 - 贝纳德对流的大规模流动组织相互联系。我们的结果基于雷利数字的数值模拟$ ra = 10^8 $以较大的纵横比（$γ= 32 $）的单元格，以确保尺度分离明显。我们提取小规模湍流的局部大小和波数，并发现这些数量的大规模变化与大规模信号的显着相关性。最值得注意的是，我们发现温度波动更强，并且在羽状区域的羽流和相反的趋势中增加了小规模运输（按$ 10 $ $ NUS $ NU $ $ NU $的订单）。这涉及墙壁距离最高$2δ_θ$（热边界层厚度）。与受影响的螺旋杆相比，通常发现局部波数在发射侧发射的局部波数更高。通过条件平均值的第二种独立方法证实了这些发现，并对小规模特性的大规模变化产生了更多见解。我们的结果对建模小规模的湍流具有影响。
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-Bénard convection. Our results are based on a numerical simulation at Rayleigh number $Ra = 10^8$ in a large aspect ratio ($Γ=32$) 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 (on the order of $10\%$ of the global Nusselt number $Nu$) in plume impacting regions and opposite trends in the plume emitting counterparts. This concerns wall distances up to $2δ_θ$ (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 modelling small-scale turbulence.
