Fluids confined in nanopores are ubiquitous in nature and technology. In recent years, the interest in confined fluids has grown, driven by research on unconventional hydrocarbon resources—shale gas and shale oil, much of which are confined in nanopores. When fluids are confined in nanopores, many of their properties differ from those of the same fluid in the bulk. These properties include density, freezing point, transport coefficients, thermal expansion coefficient, and elastic properties. The elastic moduli of a fluid confined in the pores contribute to the overall elasticity of the fluid-saturated porous medium and determine the speed at which elastic waves traverse through the medium. Wave propagation in fluid-saturated porous media is pivotal for geophysics, as elastic waves are used for characterization of formations and rock samples. In this paper, we present a comprehensive review of experimental works on wave propagation in fluid-saturated nanoporous media, as well as theoretical works focused on calculation of compressibility of fluids in confinement. We discuss models that bridge the gap between experiments and theory, revealing a number of open questions that are both fundamental and applied in nature. While some results were demonstrated both experimentally and theoretically (e.g., the pressure dependence of compressibility of fluids), others were theoretically predicted, but not verified in experiments (e.g., linear scaling of modulus with the pore size). Therefore, there is a demand for the combined experimental-modeling studies on porous samples with various characteristic pore sizes. The extension of molecular simulation studies from simple model fluids to the more complex molecular fluids is another open area of practical interest.

中文翻译：

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从分子建模到多孔固体超声实验的受限流体的弹性特性

限制在纳米孔中的流体在自然界和技术中无处不在。近年来，由于对非常规碳氢化合物资源——页岩气和页岩油的研究，其中大部分被限制在纳米孔中，对封闭流体的兴趣不断增长。当流体被限制在纳米孔中时，它们的许多特性与大量相同流体的特性不同。这些特性包括密度、凝固点、传输系数、热膨胀系数和弹性特性。限制在孔隙中的流体的弹性模量有助于流体饱和多孔介质的整体弹性，并决定弹性波穿过介质的速度。流体饱和多孔介质中的波传播对于地球物理学至关重要，因为弹性波用于表征地层和岩石样本。在本文中，我们全面回顾了在流体饱和纳米多孔介质中波传播的实验工作，以及专注于计算限制中流体压缩率的理论工作。我们讨论了弥合实验和理论之间差距的模型，揭示了许多在本质上既是基础又是应用的开放性问题。虽然一些结果在实验和理论上都得到了证明（例如，流体压缩性的压力依赖性），但其他一些结果是理论上预测的，但没有在实验中验证（例如，模量随孔径的线性缩放）。因此，需要对具有各种特征孔径的多孔样品进行组合实验建模研究。