Stability of thermal convection in two superimposed miscible viscous fluids
Stability of thermal convection in two superimposed miscible viscous fluids
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两种叠加的可混溶粘性流体中的热对流稳定性
DOI：
10.1017/s0022112002001878
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发表时间：
2002
影响因子：
3.7
通讯作者：
A. Davaille
中科院分区：
文献类型：
--
作者：
M. L. Bars;A. Davaille
采用实验室实验和边界稳定性分析相结合的方法，研究了高Prandtl数流体中两层热对流的稳定性。两种流体具有不同的密度和粘度，但不存在表面张力，界面上的化学扩散非常缓慢，可以忽略不计。密度分层稳定。研究了广泛的粘度比和层深比。对流的开始可以是平稳的，也可以是振荡的，这取决于浮力数B，即稳定的化学密度异常与不稳定的热密度异常的比率：当B低于临界值(粘度和层深比的函数)时，振荡区域发展，变形的界面和对流模式在整个储罐深度内振荡；当B大于该临界值时，分层区域发展，界面平坦，层分别对流。实验结果与边际稳定性结果吻合较好。在低瑞利数时，线性理论能很好地预测特征时间尺度和长度尺度。在较高的瑞利数时，线性理论仍然使用瑞利数和浮力数的局部值来确定哪个对流系统将首先开始，以及使用这些参数的全局值来确定哪个对流系统将持续。
The stability of two-layer thermal convection in high-Prandtl-number fluids is investigated using laboratory experiments and marginal stability analysis. The two fluids have different densities and viscosities but there is no surface tension and chemical diffusion at the interface is so slow that it is negligible. The density stratification is stable. A wide range of viscosity and layer depth ratios is studied. The onset of convection can be either stationary or oscillatory depending on the buoyancy number B, the ratio of the stabilizing chemical density anomaly to the destabilizing thermal density anomaly: when B is lower than a critical value (a function of the viscosity and layer depth ratios), the oscillatory regime develops, with a deformed interface and convective patterns oscillating over the whole tank depth; when B is larger than this critical value, the stratified regime develops, with a flat interface and layers convecting separately. Experiments agree well with the marginal stability results. At low Rayleigh number, characteristic time and length scales are well-predicted by the linear theory. At higher Rayleigh number, the linear theory still determines which convective regime will start first, using local values of the Rayleigh and buoyancy numbers, and which regime will persist, using global values of these parameters.