New paradigm to describe transport properties of fluids

What is it about?

This paper proposes for the first time a novel microscopic model able to describe simultaneously the viscosity and the self-diffusion coefficient of fluids in their whole phase diagram with an unprecedented accuracy. It is shown that this microscopic model emerges from the introduction of fractional calculus in a traditional model of condensed matter physics based on an elastic energy functional, which allows, among other things, to integrate phase transitions directly into this modeling. On the basis of a comparative analysis of a collection of published experimental data, it is proposed to apply this model to WATER in all its fluid phases, from the supercooled liquid to supercritical states at high temperatures (~1200 K) and pressures from very low values until 6 GPa.

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Why is it important?

This approach makes it possible to reproduce the water viscosity with a better accuracy than the 2008 IAPWS formulation and also with a more physically satisfying modeling of the isochors. Moreover, it allows the modeling within experimental accuracy of the translational self-diffusion data available in the literature in all water fluid phases. It is shown that the discrepancies in the literature data are only apparent and can be quantitatively explained by the different experimental configurations (e.g. geometry, calibration). Also, the formalism of the model makes it possible to understand the “anomalies” observed on the dynamic viscosity and self-diffusion coefficient and their links. In addition, some Appendices are included that strongly support the theoretical developments presented here. Some of these Appendices propose new equations of state for water that more accurately reproduce experimental data and whose extrapolation is physically more realistic than similar equations in the literature.

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