Travelling circular waves in axisymmetric rotating convection
Travelling circular waves in axisymmetric rotating convection
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DOI：
10.1017/s0022112006003077
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发表时间：
2006-11
影响因子：
3.7
通讯作者：
Juan M. Lopez;A. Rubio;F. Marques
中科院分区：
文献类型：
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作者：
Juan M. Lopez;A. Rubio;F. Marques
对普朗特数为7(实质上相当于水)的普朗特数为7的旋转圆柱内的Rayleigh-Bénard对流进行了数值研究。我们从科里奥利力和离心力两个方面考虑了旋转的影响，发现离心力起着重要的动力学作用。在最初的研究中，我们将计算限制在轴对称子空间中，在该子空间中，开始附近的对流模式由稳定的同心圆形单元组成，即所谓的目标模式，许多研究人员已经在不同条件下对其进行了研究和实验观察。当对流被驱动到足够远的时候，稳定的细胞模式让位于时间周期状态，在时间周期状态中，目标模式径向向内移动。我们已经确定了两种这样的旅行模式，主要的区别是一种是在圆柱体侧壁形成交替的暖和冷羽流，然后向内径向传播，使轴上的冷和暖羽流交替熄灭。另一种模式总是有一个冷羽落在侧壁上，相邻的暖羽周期性地分裂成两个，分裂对的最里面的部分径向向内移动。第一种模式在离心力较弱时出现，第二种模式在离心力较大时出现。由离心力驱动的大尺度经向环流有利于冷羽下降到侧壁，这是转换到第二个行进模式的原因。
Rayleigh–Bénard convection in a finite rotating cylinder of moderate aspect ratio (radius four times the depth) is investigated numerically for a fluid of Prandtl number equal to 7 (corresponding essentially to water). We consider the effects of rotation from both the Coriolis force and the centrifugal force and find that the centrifugal force plays a significant dynamic role. In this initial study, we restrict the computations to the axisymmetric subspace in which the convection patterns near onset consist of steady concentric circular cells, the so-called target patterns, which have been studied and observed experimentally under different conditions by a number of investigators. As the convection is driven far enough beyond onset, the steady cellular patterns give way to time-periodic states in which the target patterns travel radially inward. We have identified two such travelling modes, primarily distinguished by one having alternating warm and cold plumes forming at the cylinder sidewall and then propagating radially inward to quench alternately cold and warm plumes on the axis. The other mode always has a cold plume descending on the sidewall and the adjacent warm plume periodically splits into two, with the innermost of the split pair travelling radially inward. The first of these modes is found when the centrifugal force is weak and the second for stronger centrifugal force. The large-scale meridional circulation driven by the centrifugal buoyancy is seen to favour having a cold plume descending on the sidewall, accounting for the switch to the second travelling mode.