Bifurcation Sequences in Problems of Thermal Convection and of Plane Couette Flow
Bifurcation Sequences in Problems of Thermal Convection and of Plane Couette Flow
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热对流和平面库埃特流问题中的分岔序列
DOI：
10.1007/978-94-009-0253-4_17
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
R. Clever
中科院分区：
文献类型：
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作者：
F. Busse;R. Clever
从下加热的流体层中的Rayleigh-Bénard对流代表了具有最高对称度的最简单系统，在该系统中可以研究流体流动向复杂状态的转变。通过随后的分叉过程，随着控制参数的增加，占据了新的自由度，并引入了新的热、质量和动量输运机制。主要取决于流体的普朗特数，可以遵循各种分叉序列。它们都是从卷曲形式的对流开始的，因为我们将假定材料性质和关于层的中面的边界是对称的。这些分叉要么导致纽结对流、振荡纽结对流和非对称纽结振荡(Clear And Busse 1989a)，要么导致双峰对流、振荡双峰对流和轮辐型对流(Busse 1967，Frick，Busse和Clear 1983，Clear and Busse1994)，或者导致行波对流和非对称行波对流(Clear和Busse 1987,1989b)。在几种情况下，可以与实验观测结果进行比较。由分叉引入的机制可以用某些破坏的对称性来表征，并且相对独立于分叉发生的顺序。观测到的热羽形成、边界层热团喷发和平均气流产生的过程。
Rayleigh-Bénard convection in a fluid layer heated from below represents the simplest system with the highest degree of symmetry in which the transition to complex states of fluid flow can be investigated. Through the process of subsequent bifurcations new degrees of freedom are occupied and new mechanisms of heat, mass and momentum transport are introduced as the control parameter is increased. Various bifurcation sequences can be followed depending primarily on the Prandtl number of the fluid. They all start with convection in the form of rolls since we shall assume symmetry of the material properties and the boundaries about the midplane of the layer. The bifurcations lead either to knot convection, oscillatory knot convection and asymmetric knot oscillations (Clever and Busse 1989a), or to bimodal convection, oscillating bimodal convection and spoke pattern convection (Busse 1967, Frick, Busse and Clever 1983, Clever and Busse 1994), or to travelling wave convection and asymmetric travelling wave convection (Clever and Busse 1987, 1989b). Comparisons with experimental observations are possible in several cases. The mechanisms introduced by the bifurcations can be characterized by certain broken symmetries and are relatively independent of the sequence in which the bifurcations occur. The processes of thermal plume formation, eruption of thermal blobs from the boundary layers, and mean flow generation which are observed as coherent