According to classical and statistical thermodynamics, a well-mixed fluid mass has a uniform temperature and is at thermodynamic equilibrium. It independent of the gravitational field. However, large well-mixed fluid masses, for example, in atmospheres and oceans, often are isentropic. One has attributed that to the influence of gravity. This has raised the question if such masses can go to a different restricted thermodynamic equilibrium with uniform entropy. Discussions on this issue have continued for three centuries without finding a final answer. This paper presents another analysis of the question if a fluid mass under the influence of gravity may go to a restricted equilibrium state with uniform entropy. At first, it analyses previous work as a background study. Then, it describes a kinetic model for the motion of fluid parcels in a vertical fluid column. This model is the tool for studying if and how the column may go to an isentropic equilibrium. The kinetic model supports the hypothesis that a fluid column under the influence of gravity may go to a restricted equilibrium state with an isentropic temperature profile. A statically unstable column can reach that state spontaneously, while its entropy increases and gravitational potential energy decreases. The latter energy is the source of the kinetic energy for the motion of its fluid parcels, driving the internal heat transfer that results in the isentropic profile.

中文翻译：

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重力作用下流体柱的热力学平衡

根据经典和统计热力学，混合良好的流体质量具有均匀的温度并处于热力学平衡。它独立于引力场。然而，大的混合良好的流体质量，例如在大气和海洋中，通常是等熵的。有人将其归因于重力的影响。这就提出了一个问题，如果这些质量可以达到不同的具有均匀熵的受限热力学平衡。关于这个问题的讨论持续了三个世纪，没有找到最终答案。本文对重力影响下的流体质量是否可以进入具有均匀熵的受限平衡状态的问题进行了另一种分析。首先，它分析以前的工作作为背景研究。然后，它描述了垂直流体柱中流体块运动的动力学模型。该模型是研究色谱柱是否以及如何达到等熵平衡的工具。动力学模型支持在重力影响下的流体柱可能会进入具有等熵温度分布的受限平衡状态的假设。一个静态不稳定的柱子可以自发地达到那个状态，而它的熵增加而重力势能减少。后一种能量是其流体块运动的动能来源，驱动内部传热，导致等熵分布。动力学模型支持在重力影响下的流体柱可能会进入具有等熵温度分布的受限平衡状态的假设。一个静态不稳定的柱子可以自发地达到那个状态，而它的熵增加而重力势能减少。后一种能量是其流体块运动的动能来源，驱动内部传热，导致等熵分布。动力学模型支持在重力影响下的流体柱可能会进入具有等熵温度分布的受限平衡状态的假设。一个静态不稳定的柱子可以自发地达到那个状态，而它的熵增加而重力势能减少。后一种能量是其流体块运动的动能来源，驱动内部传热，导致等熵分布。