Turbulent convection for different thermal boundary conditions at the plates
Turbulent convection for different thermal boundary conditions at the plates
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DOI：
10.1017/jfm.2020.830
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发表时间：
2020-11
影响因子：
3.7
通讯作者：
N. Foroozani;D. Krasnov;J. Schumacher
中科院分区：
文献类型：
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作者：
N. Foroozani;D. Krasnov;J. Schumacher
摘要采用三维直接数值模拟方法研究了底板和顶板不同热边界条件对湍流Rayleigh-Bénard对流的动力学和统计特性的影响。流动演变在一个封闭的圆柱体的纵横比为$\varGamma =1/2$在空气中的普朗特数$Pr=0.7$和瑞利数$Ra=10^7$和液体金属合金GaInSn在$Pr=0.033$和$Ra=10^7$，$10^8$。对于每种情况，我们在流体体积的顶部和底部应用三种不同的热边界条件，同时使固体侧壁绝热：（i）固定温度，（ii）固定热通量和（iii）共轭热传递，其将工作流体中的温度和热通量耦合到包围湍流的厚的固体板的温度和热通量。与等温板相比，共轭传热的情况下，整体传热提高了19%。两个普朗特数中较低的差异减小;对于全球湍流动量传递，它们通常保持较小。平均温度分布和均方根速度波动的影响令人惊讶的微弱。当比较定温和共轭传热的情况时，局部热边界尺度的分布出现最大的差异。我们还讨论了我们的结果，鉴于在液态金属实验的实验不确定性。
Abstract The influence of the different thermal boundary conditions at the bottom and top plates on the dynamics and statistics of a turbulent Rayleigh–Bénard convection flow is studied in three-dimensional direct numerical simulations. The flow evolves in a closed cylinder with an aspect ratio of $\varGamma =1/2$ in air for a Prandtl number $Pr=0.7$ and a Rayleigh number $Ra=10^7$ and in the liquid metal alloy GaInSn at $Pr=0.033$ and $Ra=10^7$, $10^8$. We apply for each case three different thermal boundary conditions at the top and bottom of the fluid volume while leaving the solid sidewall thermally insulated: (i) fixed temperature, (ii) fixed heat flux and (iii) conjugate heat transfer which couples the temperature and heat flux in the working fluid to that of the finitely thick, solid plates enclosing the turbulent flow. The global heat transfer is enhanced by up to 19 % for the conjugate heat transfer case in comparison to that of isothermal plates. The differences decrease for the lower of the two Prandtl numbers; they remain generally smaller for the global turbulent momentum transfer. Mean temperature profiles and root mean square velocity fluctuations are surprisingly weakly affected. The largest difference appears for the distribution of local thermal boundary scales when the cases of fixed temperature and of conjugate heat transfer are compared. We also discuss our results in view to experimental uncertainties in liquid metal experiments.