Conditional statistics of thermal dissipation rate in turbulent Rayleigh-Bénard convection
Conditional statistics of thermal dissipation rate in turbulent Rayleigh-Bénard convection
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DOI：
10.1140/epje/i2012-12108-8
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发表时间：
2012-10
期刊：
影响因子：
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通讯作者：
M. Emran;J. Schumacher
中科院分区：
文献类型：
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作者：
M. Emran;J. Schumacher
采用三维直接数值模拟方法，研究了圆柱形单胞内湍流Rayleigh-Bénard对流热耗散率的统计特性，其中Prandtl数Pr = 0.7，长宽比Γ= 1。瑞利数Ra在107 ~ 3 × 1010之间。我们应用的标准，分解成两个不相交的子集的细胞体积：羽为主的部分和湍流背景部分。以羽流为主的集合在整个单元体积上延伸，并且不限于边界层。它形成了一个复杂的空间骨架，在对流单体中的热量传输，其体积分数随着瑞利数的增加而减少。后一个发现也成立时的阈值，分开两个子卷，是不同的。瑞利数的平均时刻和概率密度函数的热耗散的依赖性进行了分析的子体积和相关的对流体积的其他可能的划分，如边界层和散装。最大的热耗散事件总是发现在羽流为主的子集。
The statistical properties of the thermal dissipation rate in turbulent Rayleigh-Bénard convection in a cylindrical cell are studied by means of three-dimensional direct numerical simulations for a fixed Prandtl numberPr= 0.7 and aspect ratioΓ= 1. The Rayleigh numbersRaare between 107and 3 × 1010. We apply a criterion that decomposes the cell volume into two disjoint subsets: the plume-dominated part and the turbulent background part. The plume-dominated set extends over the whole cell volume and is not confined to the boundary layers. It forms a complex spatial skeleton on which the heat is transported in the convection cell and its volume fraction decreases with increasing Rayleigh number. The latter finding holds also when the threshold, which separates both subvolumes, is varied. The Rayleigh number dependence of the mean moments and probability density functions of the thermal dissipation are analyzed on the subvolumes and related to other possible divisions of the convection volume, such as into boundary layer and bulk. The largest thermal dissipation events are always found in the plume-dominated subset.