Chatterjee Atanu, Yadati Yash, Mears Nicholas, Iannacchione Germano
Department of Physics and the Order-Disorder Phenomena Lab, Worcester Polytechnic Institute, MA, 01605, USA.
Sci Rep. 2019 Jul 23;9(1):10615. doi: 10.1038/s41598-019-47127-2.
A challenge in fundamental physics and especially in thermodynamics is to understand emergent order in far-from-equilibrium systems. While at equilibrium, temperature plays the role of a key thermodynamic variable whose uniformity in space and time defines the equilibrium state the system is in, this is not the case in a far-from-equilibrium driven system. When energy flows through a finite system at steady-state, temperature takes on a time-independent but spatially varying character. In this study, the convection patterns of a Rayleigh-Bénard fluid cell at steady-state is used as a prototype system where the temperature profile and fluctuations are measured spatio-temporally. The thermal data is obtained by performing high-resolution real-time infrared calorimetry on the convection system as it is first driven out-of-equilibrium when the power is applied, achieves steady-state, and then as it gradually relaxes back to room temperature equilibrium when the power is removed. Our study provides new experimental data on the non-trivial nature of thermal fluctuations when stable complex convective structures emerge. The thermal analysis of these convective cells at steady-state further yield local equilibrium-like statistics. In conclusion, these results correlate the spatial ordering of the convective cells with the evolution of the system's temperature manifold.
基础物理学尤其是热力学中的一个挑战是理解远离平衡态系统中的涌现秩序。在平衡态时，温度起着关键热力学变量的作用，其在空间和时间上的均匀性定义了系统所处的平衡态，但在远离平衡态的驱动系统中并非如此。当能量在稳态下流经有限系统时，温度呈现出与时间无关但随空间变化的特性。在本研究中，稳态瑞利 - 贝纳德流体池的对流模式被用作一个原型系统，在该系统中对温度分布和涨落进行时空测量。热数据是通过对对流系统进行高分辨率实时红外量热法获得的，该系统在施加功率时首先被驱动至非平衡态，达到稳态，然后在去除功率时逐渐弛豫回到室温平衡态。我们的研究提供了关于稳定复杂对流结构出现时热涨落的非平凡性质的新实验数据。对这些稳态对流池的热分析进一步得出类似局部平衡的统计数据。总之，这些结果将对流池的空间有序性与系统温度流形的演化联系起来。
