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Layer formation in double-diffusive convection over resting and moving heated plates
Theoretical and Computational Fluid Dynamics ( IF 3.4 ) Pub Date : 2019-07-02 , DOI: 10.1007/s00162-019-00499-7
Florian Zaussinger , Friedrich Kupka

We present a numerical study of double-diffusive convection characterized by a stratification unstable to thermal convection, while at the same time a mean molecular weight (or solute concentration) difference between top and bottom counteracts this instability. Convective zones can form in this case either by the stratification being locally unstable to the combined action of both temperature and solute gradients or by another process, the oscillatory double-diffusive convective instability, which is triggered by the faster molecular diffusivity of heat in comparison with that one of the solute. We discuss successive layer formation for this problem in the case of an instantaneously heated bottom (plate) which forms a first layer with an interface that becomes temporarily unstable and triggers the formation of further, secondary layers. We consider both the case of a Prandtl number typical for water (oceanographic scenario) and of a low Prandtl number (giant planet scenario). We discuss the impact of a Couette like shear on the flow and in particular on layer formation for different shear rates. Additional layers form due to the oscillatory double-diffusive convective instability, as is observed for some cases. We also test the physical model underlying our numerical experiments by recovering experimental results of layer formation obtained in laboratory setups.

中文翻译:

在静止和移动的加热板上双扩散对流中的层形成

我们提出了双扩散对流的数值研究,其特征是分层对热对流不稳定,同时顶部和底部之间的平均分子量(或溶质浓度)差异抵消了这种不稳定性。在这种情况下,对流区可以通过分层对温度和溶质梯度的共同作用而局部不稳定或由另一个过程,振荡双扩散对流不稳定性而形成,与热的分子扩散速度相比,该过程由更快的分子扩散率触发。那溶质之一。在瞬时加热的底部(板)形成第一层的情况下,我们讨论了这个问题的连续层形成,该第一层的界面变得暂时不稳定并触发进一步的第二层的形成。我们考虑了水的典型普朗特数(海洋场景)和低普朗特数(巨行星场景)的情况。我们讨论了类似库埃特的剪切对流动的影响,特别是对不同剪切速率下的层形成的影响。正如在某些情况下所观察到的那样,由于振荡双扩散对流不稳定性而形成附加层。我们还通过恢复在实验室设置中获得的层形成的实验结果来测试我们数值实验背后的物理模型。正如在某些情况下所观察到的那样,由于振荡双扩散对流不稳定性而形成附加层。我们还通过恢复在实验室设置中获得的层形成的实验结果来测试我们数值实验背后的物理模型。正如在某些情况下所观察到的那样,由于振荡双扩散对流不稳定性而形成附加层。我们还通过恢复在实验室设置中获得的层形成的实验结果来测试我们数值实验背后的物理模型。
更新日期:2019-07-02
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