Large interface deformation in two-layer thermal convection of miscible viscous fluids
Large interface deformation in two-layer thermal convection of miscible viscous fluids
复制标题
混相粘性流体两层热对流中界面大变形
DOI：
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发表时间：
2004
影响因子：
3.7
通讯作者：
A. Davaille
中科院分区：
文献类型：
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作者：
M. L. Bars;A. Davaille
实验研究了界面大变形条件下的双层热对流。这两种流体具有不同的密度和粘度，但在界面处既没有表面张力也没有化学扩散。初始密度分层是稳定的，但可以通过热效应逆转。描述了两种不同的界面变形机制：（1）由于各层内部对流的纯热特征可以局部和部分地使界面变形，导致动态形貌;（ii）当有效浮力数（稳定化学密度异常与不稳定热密度异常之比）达到临界值，发生全层状态，系统完全不稳定，两层中的一层侵入另一层形成大圆顶。如果粘度比足够大（即，${>}，5 $），则可以观察到几个连续的脉动。典型的规模（时间，长度，温度过剩，速度）和行为（喷流方向，形状）确定每种情况下。这两个特征都只是短暂的状态：由于搅拌，系统系统系统地向单层瑞利-贝纳德对流发展。然而，与热对流的特征时间尺度相比，这种瞬态可以持续很长时间。
Laboratory experiments have been performed to study two-layer thermal convection with large interface deformations. The two fluids have different densities and viscosities but there is neither surface tension nor chemical diffusion at the interface. The initial density stratification is stable, but can be reversed by thermal effects. Two different mechanisms of interface deformation are described: (i) purely thermal features due to convection inside each layer independently can locally and partially deform the interface, leading to dynamic topography; (ii) when the effective buoyancy number (the ratio of the stabilizing chemical density anomaly to the destabilizing thermal density anomaly) reaches a critical value, a whole-layer regime takes place, where the system is fully destabilized and one of the two layers invades the other one in the form of large domes. Several successive pulsations can be observed provided the viscosity ratio is large enough (i.e. ${>},5$). Typical scales (time, length, temperature excess, velocity) and behaviours (direction of spouting, shapes) are determined for each case. Both features are only transient states: because of stirring, the system systematically evolves towards one-layer Rayleigh–Bénard convection. However, this transient state can persist for a very long time compared to the characteristic time scale of thermal convection.