Thermal convection in binary fluid mixtures with a weak concentration diffusivity, but strong solutal buoyancy forces.
Thermal convection in binary fluid mixtures with a weak concentration diffusivity, but strong solutal buoyancy forces.
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二元流体混合物中的热对流，浓度扩散系数较弱，但溶质浮力较强。
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
H. Pleiner
中科院分区：
文献类型：
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作者：
A. Ryskin;H. Müller;H. Pleiner
在溶质扩散系数较弱但分离比较大的极限条件下，研究了二元液体混合物中的热对流。典型的例子是胶体悬浮液，如铁磁流体。由于颗粒尺寸在分子长度尺度上很大，颗粒迁移率非常小，在大多数情况下可以忽略浓度动力学。然而，这种简化并不适用于热对流：由于这些材料明显的Soret效应与相当大的溶质膨胀相结合，导致溶质浮力占主导地位。事实上，对流运动被发现在瑞利数远低于单组分液体的临界阈值时开始。非线性分析表明，在静止对流运动状态下，振幅很快饱和。
Thermal convection in binary liquid mixtures is investigated in the limit where the solutal diffusivity is weak, but the separation ratio is large. Representative examples are colloidal suspensions such as ferrofluids. With a grain size being large on molecular length scales, the particle mobility is extremely small, allowing to disregard the concentration dynamics in most cases. However, this simplification does not hold for thermal convection: Due to the pronounced Soret effect of these materials in combination with a considerable solutal expansion, the resulting solutal buoyancy forces are dominant. Indeed, convective motion is found to set in at Rayleigh numbers well below the critical threshold for single-component liquids. A nonlinear analysis demonstrates that the amplitude quickly saturates in a state of stationary convective motion.