Laboratoire des Fluides Complexes et leurs Réservoirs, IPRA, UMR5150, E2S-Univ Pau & Pays Adour/CNRS/Total, 64600 Anglet, France.
Universitá degli Studi di Milano, Via Celoria 13, 20013 Milano, Italy.
Phys Rev E. 2019 Jan;99(1-1):012602. doi: 10.1103/PhysRevE.99.012602.
Nonequilibrium temperature and concentration fluctuations inside a binary liquid mixture under the action of a temperature gradient relax back to equilibrium either due to conduction and diffusion at large wave numbers, or due to the quenching determined by gravity at small wave numbers. We investigate the dynamics of nonequilibrium fluctuations in a binary liquid mixture of polystyrene and toluene heated from above under stationary conditions in a thermodiffusion experiment. We show that the strong gravitational stabilization at small wave numbers determines the appearance of propagating modes of nonequilibrium fluctuations as detected through the structure function of shadowgraph images. The propagating modes are the combined effect of temperature and velocity nonequilibrium fluctuations induced by the buoyancy force. The experimental results are in good agreement with a fluctuating hydrodynamics theroretical model including the coupling of fluctuations of velocity, temperature and concentration.
在温度梯度的作用下，二元液体混合物内部的非平衡温度和浓度涨落会通过大波数的传导和扩散，或者通过小波数的重力猝灭而回到平衡状态。我们在一个热扩散实验中，对在上方加热的聚苯乙烯和甲苯二元液体混合物的非平衡涨落动力学进行了研究。我们表明，在小波数下，强重力猝灭决定了非平衡涨落传播模式的出现，这可以通过阴影图像的结构函数来检测到。传播模式是由浮力引起的温度和速度非平衡涨落的组合效应。实验结果与包括速度、温度和浓度涨落耦合的随机流体力学理论模型吻合较好。
