Persona: Hernández Rodríguez, Julio
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Hernández Rodríguez
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Publicación A comparative study of two open-source state-of-the-art geometric VOF methods(Elsevier, 2023-01-15) Esteban Paz, Adolfo; Gómez del Pino, Pablo Joaquín; López, Joaquín; Zanzi, Claudio; Roenby, Johan; Hernández Rodríguez, JulioWe present a systematic study of geometric volume of fluid (VOF) methods provided in the gVOF and TwoPhaseFlow packages, which include algorithms that are among the most accurate proposed in recent years. In addition to contributing to their further validation, the main purpose is to evaluate, in terms of accuracy and efficiency, the relative advantages of the advection and reconstruction algorithms used in the two packages (mainly, FMFPA-CLCIR and isoAdvector-plicRDF, respectively), and to investigate the suitability of combining them. Since TwoPhaseFlow is available in OpenFOAM, gVOF was also coupled with this open source CFD toolbox to maintain the same conditions in common solvers when obtaining and comparing their results, including discretization schemes, tolerances and meshes. For the same reason, identical computational resources were also maintained. The use of a common software and hardware framework that guarantees strictly the same simulation conditions overcomes many of the limitations and uncertainties of comparisons made in previous studies. Several reconstruction and advection tests are presented, showing the differences between the algorithms in terms of accuracy, as measured by several error norms, and in terms of efficiency, as measured by CPU times consumed. Simulations of the rise of a bubble and the impact of a drop on a pool were also performed, in which the VOF methods were coupled to the same solver of the Navier–Stokes equations, and the results obtained with the two combinations of algorithms FMFPA-CLCIR and isoAdvector-plicRDF are compared with each other and, in the case of the second test, with our own experimental results. The relative advantages and limitations of the analyzed algorithms are discussed, and it is suggested that a combination of isoAdvector for advection and CLCIR for reconstruction can provide a good compromise between accuracy and efficiency.Publicación A new isosurface extraction method on arbitrary grids(Elsevier, 2021-11) López, Joaquín; Esteban Paz, Adolfo; Hernández Rodríguez, Julio; Gómez del Pino, Pablo Joaquín; Zamora, Rosendo; Zanzi, Claudio; Faura, FélixThe development of interface-capturing methods (such as level-set, phase-field or volume of fluid (VOF) methods) for arbitrary 3D grids has further highlighted the need for more accurate and efficient interface reconstruction procedures. In this work, we propose a new method for the extraction of isosurfaces on arbitrary polyhedra that can be used with advantage for this purpose. The isosurface is extracted from volume fractions by a general polygon tracing procedure, which is valid for convex or non-convex geometries, even with non-planar faces. The proposed method, which can be considered as an extension of the marching cubes technique, produces consistent results even for ambiguous situations in polyhedra of arbitrary shape. To show the reproducibility of the results presented in this work, we provide the open source library isoap, which has been developed to implement the proposed method and includes test programs to demonstrate the successful extraction of isosurfaces on several grids with polyhedral cells of different types. We present results obtained not only for isosurface extraction from discrete volume fractions resulting from a volume of fluid method, but also from data sets obtained from implicit mathematical functions and signed distances to scanned surfaces. The improvement provided by the proposed method for the extraction of isosurfaces in arbitrary grids will also be very useful in other fields, such as CFD visualization or medical imaging.Publicación On polytope intersection by half-spaces and hyperplanes for unsplit geometric volume of fluid methods on arbitrary grids(Elsevier, 2024-07) López, Joaquín; Hernández Rodríguez, Julio; https://orcid.org/0000-0002-7069-244XSeveral tools with improved accuracy and computational efficiency, along with added capabilities, are presented for performing analytic and geometric operations involving intersections between half-spaces or hyperplanes and 2- or 3-polytopes (polygons or polyhedra, either convex or non-convex) that typically arise in advanced volume of fluid (VOF) methods on arbitrary grids. In particular, tools for the intersection between a polyhedron and a half-space, and for the computation of the interface position to cut off a given area/volume fraction from an arbitrary polygonal/polyhedral grid cell in PLIC (piecewise linear interface calculation) reconstruction have been improved in terms of accuracy and computational efficiency. In addition, specific tools are also proposed for (1) the intersection in 3D between a planar polygon and a half-space, and the computation of the resulting intersected area, which can be useful for unsplit methods based on wetted-area time-integration advection (WATIA) schemes, and for (2) the efficient computation of the geometric center of the set of clipped vertices and volume resulting from the intersection between an arbitrary polyhedron and a half-space, which can be useful for, respectively, several PLIC reconstruction methods and unsplit methods based on fluid-volume intersection advection (FVIA) schemes. Finally, a convenient strategy to perform the recursive intersections required during the advection step in advanced geometric VOF methods based on FVIA schemes is also proposed. To assess the performance and accuracy of the proposed tools, different tests were carried out for several convex and non-convex polytopes. Speedups of ×5 and improvements in accuracy of up to 5 orders of magnitude over previous tools have been achieved for certain geometries and operations. The proposed tools have been included in two advection methods (an FVIA method and a new WATIA method proposed in this work) and in a PLIC reconstruction method to demonstrate their improved performance and capabilities on structured and unstructured grids.Publicación A contact line force model for the simulation of drop impacts on solid surfaces using volume of fluid methods(Elsevier, 2023-09-15) Esteban Paz, Adolfo; Gómez del Pino, Pablo Joaquín; Zanzi, Claudio; López, Joaquín; Bussmann, Markus; Hernández Rodríguez, JulioCharacterizing the contact line dynamics on solid walls is often a crucial problem encountered in the simulation of complex interfacial unsteady flows, such as drop impacts on solid surfaces. In this work, a new model is proposed to reproduce the contact line dynamics in a simple but effective way, based on introducing in the momentum equation a force term proportional to the deviation of the calculated contact angle from the value predicted by a dynamic model that takes into account wettability hysteresis. The model has been implemented in a volume of fluid (VOF) method and is applied to the simulation of drop impacts leading to deposition outcomes, although it could be extended to other interface tracking methods and is also applicable to more complex drop impacts involving fingering and splashing. Numerous tests have been performed to evaluate the accuracy and robustness of the proposed model over a wide range of Reynolds and Weber numbers. The results substantially improve those obtained by imposing only the contact angle as a boundary condition at the contact line, and satisfactorily predict a variety of experimental results from the literature for very different impact and wettability conditions.