Three-dimensional phase-field simulations of water freezing and thawing at pore-scale
| Autor: | Strachota, Pavel |
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| Rok vydání: | 2024 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| Popis: | This work deals with numerical simulation of water freezing and thawing in a complex three-dimensional geometry of a porous medium. The porous structure is represented by a virtual container filled with glass beads. Phase transition modeling is approached at both macro-scale and micro-scale, combining heat transfer in a heterogeneous medium and a phase-field approximation of the Gibbs-Thomson relation by means of the Allen-Cahn equation. The formulation of the model contains novel components tailored for the given purpose. At the macro-scale, surface tension effects are negligible and phase transition focusing based on temperature can replace the Allen-Cahn equation. In contrast to that, simulations of equilibrium states at the micro-scale allow to eliminate the heat equation by assuming constant supercooling. For numerical solution, an efficient hybrid parallel algorithm based on the finite volume method and the Runge-Kutta-Merson solver with adaptive time stepping are employed. The results of different model variants at different scales are discussed. In a parametric study, the full phase-field model is demonstrated to deliver consistent results across a wide range of surface tension values, exhibiting curvature-induced premelting if surface tension is artificially exaggerated. As surface tension tends to the realistic values, the results of the phase-field approach those of the simplifed temperature-driven phase transition model. In addition, micro-scale simulations of water freezing at different supercooling values aim to predict the unfrozen water content and compare the results with data from literature. Numerical stability, accuracy, and computational costs are also discussed. Comment: Substantially improved version; the material on particle collisions was extended to full DEM simulations and published elsewhere (https://zenodo.org/doi/10.5281/zenodo.11091407). Micro-scale phase-field simulations have been added, evaluating the presence of unfrozen water content (UWC) below zero Celsius. Validation against experimental and theoretical data has been discussed |
| Databáze: | arXiv |
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