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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, Julio
We 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.
Complex Ginzburg–Landau Equation with Generalized Finite Differences
(MDPI, 2020-12-20) Salete Casino, Eduardo; Vargas Ureña, Antonio Manuel; García, Ángel; Negreanu, Mihaela; Benito Muñoz, Juan J.; Ureña, Francisco
In this paper we obtain a novel implementation for irregular clouds of nodes of the meshless method called Generalized Finite Difference Method for solving the complex Ginzburg–Landau equation. We derive the explicit formulae for the spatial derivative and an explicit scheme by splitting the equation into a system of two parabolic PDEs. We prove the conditional convergence of the numerical scheme towards the continuous solution under certain assumptions. We obtain a second order approximation as it is clear from the numerical results. Finally, we provide several examples of its application over irregular domains in order to test the accuracy of the explicit scheme, as well as comparison with other numerical methods.
Computational study of the Nitrogen-16 source term in the ITER vacuum vessel cooling circuit through the coupling of system-level analysis code and CFD
(Elsevier, 2024-08) De Pietri, Marco; Fiorina, C.; Le Tonqueze, Y.; Juárez Mañas, Rafael
In ITER, the evaluation of the activated water radiation source and its impact on the radiological levels is necessary to demonstrate compliance with the safety requirements. The use of simplified or conservative approaches often results in the application of expensive constraints on the installation that impact its economics, operations, and construction schedule. In this work, we propose a novel methodology to calculate the activated water source term with a higher degree of realism. The methodology is based on the coupling of a system-level code with a Computational Fluid Dynamics (CFD) code in an explicit, one-way approach. We apply this methodology to the evaluation of the 16N radioisotope within the ITER Vacuum Vessel Primary Heat Transfer System (VV-PHTS) cooling circuit in a steady-state and transient scenarios. We chose this system since previous analyses of the VV-PHTS were done with simple, ad-hoc calculations that yielded results that differed by up to a factor of five, underscoring a higher level of uncertainty. As a result, we generate a computational model of the source term that can be used to evaluate the radiological condition surrounding the cooling systems during the operations.
Construction of GVR weight windows maps from very low density transport simulations
(Elsevier, 2024-05) Farga Niñoles, Gonzalo; Ogando Serrano, Francisco M.; Alguacil Orejudo, Javier; Sauvan, Patrick
Fusion-related facilities present relevant neutron radiation fields even after penetrating through a considerable thickness of shielding material. Neutronic analyses performed via Monte Carlo codes, then, need Global Variance Reduction (GVR) techniques so that low statistical uncertainty is reached efficiently throughout the geometry. Mesh-based Weight Windows is a flexible methodology used extensively for variance reduction purposes, both for Local and Global Variance Reduction. Purely stochastic GVR methodologies based on Weight Windows usually construct weight maps so that they are proportional to the forward particle flux, which is unknown a priori. Therefore, an iterative cycle is established. In each iteration, a weight map is obtained from the forward flux that allows the next iteration to reach further into the geometry, until all of it is populated. However, this iterative cycle may take a considerable amount of computer time, as many iterations are needed to fully populate the geometry. An alternative to achieve relevant penetration in a single iteration is to perform calculations at very low densities. However, a reconstruction method is needed to estimate the flux at the real density. This work studies a scheme to reconstruct the fluxes from low density calculations and compares it to already existing techniques.
Continuous and discrete periodic asymptotic behavior of solutions to a competitive chemotaxis PDEs system
(Elsevier, 2021-04) Negreanu, Mihaela; Vargas Ureña, Antonio Manuel
In this paper we study the continuous and full discrete versions of a parabolic-parabolic-elliptic system with periodic terms that serves as a model for some chemotaxis phenomena. This model appears naturally in the interaction of two biological species and a chemical. The presence of the periodic terms has a strong impact on the behavior of the solutions. Some conditions on the system’s data are given that guarantee the global existence of solutions that converge to periodical solutions of an associated ODE’s system. Further, we analyze the discretized version of the model using a Generalized Finite Difference Method (GFDM) and we confirm that the properties of the continuous model are also preserved for the resulting discrete model. To this end, we prove the conditional convergence of the numerical model and study some practical examples.
Cost-Effective Arduino-Based SPWM Control of an Inverter for Training Menacho
(IEEE Xplore, 2021-12) Menacho, Antonio; Blázquez Merino, Manuel; Plaza,Pedro; San Cristóbal Ruiz, Elio; Martín Gutiérrez, Sergio; Clara Pérez; Manuel Castro; Ramón Carrasco Borrego
In this work, a cost-effective sine pulse-width modulation (SPWM) control of an inverter has been implemented using Arduino UNO microcontroller, which can be used with various power stages. The proposed model is focused on power electronics training or learning. It allows users to practice the control of an inverter without the need to be in a face-to-face laboratory. The proposed model facilitates remote experimentation to acquire the required knowledge or competencies.
Cracks in Arch Dams: an overview of documented instances
(MDPI, 2024-08-27) Conde, André; Toledo, Miguel Á.; Salete Casino, Eduardo
It is essential to understand how failure mechanisms work in arch dams and, in particular, their most common manifestation: cracking. In this paper, the different types of cracking are explained in terms of their causes and consequences. Then, an exhaustive literature review is carried out that results in a detailed compilation of the characteristics of 38 cracked arch dams from all over the world, including crack characteristics (zone, position, dimensions and probable cause). This review is restricted to only those dams for which information on the position of the cracks or dam displacements is publicly available. As part of the review, a brief summary of key data for each dam is included, as well as a compilation of published crack diagrams. The positions of the cracks of all the dams are classified using diagrams in relation to the type of dam and the origin of the crack. Finally, the distribution of some dam parameters and crack features is analyzed by studying the relationships between them.
Cutting Parameter Selection for Efficient and Sustainable Repair of Holes Made in Hybrid Mg–Ti–Mg Component Stacks by Dry Drilling Operations
(MDPI, 2018-08-07) Rubio Alvir, Eva María; Villeta, María; Valencia, José Luis; Sáenz de Pipaón, José Manuel; MDPI
Drilling is one of the most common machining operations in the aeronautic and aerospace industries. For assembling parts, a large number of holes are usually drilled into the parts so that they can be joined later by rivets. As these holes are subjected to fatigue cycles, they have to be checked regularly for maintenance or repair, since small cracks or damage in its contour can quickly cause breakage of the part, which can have dangerous consequences. This paper focuses on finding the best combinations of cutting parameters to perform repair and maintenance operations of holes in stacked hybrid magnesium–titanium–magnesium components in an efficient, timely, and sustainable (without lubricants or coolants) manner, under dry drilling conditions. For the machining trials, experiments were designed and completed. A product of a full factorial 23 and a block of two factors (3 2) was used with surface roughness as the response variable measured as the mean roughness average. Analysis of variance (ANOVA) was used to examine the results. A set of optimized tool and cutting conditions is presented for performing dry drilling repair operations.
Data analytics-driven selection of die material in multimaterial co-extrusion of Ti-Mg alloys
(MDPI, 2024-03-10) Fernández Bermejo, Daniel; Rodríguez Prieto, Álvaro; Camacho López, Ana María
Abstract: Selection of the most suitable material is one of the key decisions to be taken at the design stage of a manufacturing process. Traditional approaches as Ashby maps based on material properties are widely used in the industry. However, in the production of multimaterial components, the criteria for the selection can include antagonistic approaches. The aim of this work is the implementation of a methodology based on the results of process simulations for several materials and classify them by applying an advanced data analytics method based on Machine Learning (ML), in this case the Support Vector Regression (SVR) and Multi-Criteria Decision Making (MCDM) meth- odologies, specifically Multi-criteria Optimization and Compromise Solution (VIKOR) combined with Entropy weighting methods. In order to do this, a Finite Element Model (FEM) has been built to evaluate the extrusion force and the die wear in a multi-material co-extrusion process of bimetallic Ti6Al4V-AZ31B billets. After applying SVR and VIKOR combined with Entropy weighting methodologies, a comparison has been established based on the material selection and complexity of the methodology used, resulting that material chosen in both methodologies is very similar and MCDM method is easier to implement because there is no need of evaluate the error of the prediction model and the time for data preprocessing is less than the time needed in SVR. This new methodology is proven to be effective as alternative to the traditional approaches and aligned with the new trends in the industry based on simulation and data analytics.
Development of a methodology to estimate the statistical SDR uncertainty with R2S-UNED
(ELSEVIER, 2021) Alguacil Orejudo, Javier; Catalán Pérez, Juan Pablo; Sanz Gozalo, Javier; Sauvan, Patrick; https://orcid.org/0000-0002-9128-8817
The Rigorous-Two-Steps (R2S) is one of the most useful methods to estimate the Shutdown Dose Rate (SDR). The most advanced R2S tools couple neutron and photon transport, which are often simulated using Monte Carlo (MC) codes, through an activation simulation using mesh-based techniques to improve the spatial resolution of the neutron flux and the decay gamma source. One of the problems of the methodology is that the statistical uncertainty of the neutron flux due to the MC method used by the transport codes is not considered by most R2S implementations. Consequently, larger tolerance must be assumed affecting to the design of the nuclear facilities. This article describes a scheme allowing the calculation of the SDR statistical uncertainty without any additional assumptions than those used in the R2S methodology. The approach proposed in this article is suitable for cell- and mesh-based R2S implementations. In this work, the methodology was implemented in the R2S-UNED code. The accurate application of the methodology requires the full the neutron flux uncertainty (covariance matrix) as input data. MCNP was modified to calculate this matrix, although, it cannot be calculated for most of the realistic R2S simulations due to its size. If that is the situation, we propose a guideline to reduce the size of the covariance matrix to be calculated according to its element contribution to the SDR. When this guideline cannot be applied, the methodology still allows calculating the upper and lower SDR uncertainty bounds. In this article, the guideline is applied to the calculation of the SDR uncertainty in the computational benchmark of ITER. In addition, we also study the possible impact of the neutron flux correlation degree on the SDR uncertainty in this benchmark.
Doubling constants and spectral theory on graphs
(Elsevier, 2023-02-08) Durand Cartagena, Estibalitz; Soria, Javier; Tradacete, Pedro
We study the least doubling constant among all possible doubling measures defined on a (finite or infinite) graph G. We show that this constant can be estimated from below by 1+r(AG), where r(AG) is the spectral radius of the adjacency matrix of G, and study when both quantities coincide. We also illustrate how amenability of the automorphism group of a graph can be related to finding doubling minimizers. Finally, we give a complete characterization of graphs with doubling constant smaller than 3, in the spirit of Smith graphs.
Dust contamination of Divertor Remote Handling System in ITER Hot Cell: A novel approach to model complex superficial radiation sources
(ELSEVIER, 2024) Martínez Albertos, Pablo; Sauvan, Patrick; Catalán Pérez, Juan Pablo; F., Javier; Le Tonquèze, Yannick; Hamilton, David Thomas; Juárez Mañas, Rafael
Activated dust produced by the erosion of plasma-facing components entails a significant radiation source for ITER and, generally, for all tokamaks aiming for operation under high neutron exposure. In-Vessel remote-handling operations will mobilise the dust, which will be deposited on the remote-handling tools used, for which hands-on maintenance is expected. To ensure safe maintenance of the remote-handling equipment, a dedicated decontamination process in the Hot Cell is required. Evaluating the radiation fields produced by the contaminated equipment is central to minimising radiation exposure to personnel. In this study, we present a nuclear analysis of the Divertor Remote Handling System during its transfer and decontamination process. Past computational limitations regarding superficial sources definition and high uncertainties on the dust model have been overcome by implementing a novel methodology and following an alternative approach. Two surface-dependent dust distributions over the complex geometry surfaces were considered to evaluate the dose rates according to the different contamination levels during the process phases. A scoping analysis was performed to determine the amount of dust that would comply with project requirements in each phase of the process. Improvement margins were identified in the quantification of the amount of dust and Hot Cell layout.
Easy Development of Industry 4.0 Remote Labs
(MDPI, 2024) Rejón Gómez, Carlos; Martín Gutiérrez, Sergio; Robles Gómez, Antonio
Acquiring hands-on skills is nowadays key for Engineers today in the context of Industry 1 4.0. However, it is not always possible to do this in person. Therefore, it is essential to be able to do 2 this from a remote location. To support the development of remote labs for experimentation, this work 3 proposes the development of an open Industry 4.0 remote platform, which can be easily configured 4 and scaled to develop new remote labs for IoT (Internet of Things), cybersecurity, perception systems, 5 robotics, AI (Artificial Intelligence), etc. Over time, these capabilities will enable the development of 6 sustainable Industry 4.0 remote labs. These labs will coexist on the same Industry 4.0 platform, as 7 our proposed Industry 4.0 remote platform is capable of connecting multiple heterogeneous types 8 of devices for remote programming. In this way, it is possible to easily design open remote labs for 9 the digital transition to Industry 4.0 in a standardized way, which is the main research goal of our 10 In4Labs project. Several users are already conducting a series of IoT experiments within our remote 11 Industry 4.0 platform, providing useful recommendations to be included in future versions of the 12 platform.
Effect of Process Parameters and Definition of Favorable Conditions in Multi-Material Extrusion of Bimetallic AZ31B–Ti6Al4V Billets
(MDPI) Fernández Bermejo, Daniel; Rodríguez Prieto, Álvaro; Camacho López, Ana María
This paper investigates the extrusion process to manufacture bimetallic cylinders combining a magnesium alloy core (AZ31B) and a titanium alloy sleeve (Ti6Al4V) of interest in aeronautical applications. A robust finite element model has been developed to determine the most influential parameters and to study the effect of them on the extrusion force and damage induced by means of Design of Experiments (DOE) and Taguchi method. The results show that the most influential parameters in the extrusion forces are the friction between sleeve and container/die and the height of the cylinder; and the less influential ones are the process temperature and ram speed. Moreover, minimum values of forces along with low damage can be reached by favorable interface contact conditions, minimizing the friction at the core-container/die interface, as the main influencing factor; followed by the geometrical dimensions of the billet, being the billet height more important when paying attention to the minimum forces, and being the core diameter when considering the minimum damage as the most important criterion. The results can potentially be used to improve the efficiency of this kind of extrusion process and the quality of the extruded part that, along with the use of lightweight materials, can contribute to sustainable production approaches.
An effective numeric method for different formulations of the elastic wave propagation problem in isotropic medium
(Elsevier, 2021-08) Salete Casino, Eduardo; Vargas Ureña, Antonio Manuel; García, Ángel; Benito Muñoz, Juan J.; Ureña, Francisco; Ureña, Miguel
This paper shows how the Generalized Finite Difference Method allows the same schemes in differences to be used for different formulations of the wave propagation problem. These formulations present pros and cons, depending on the type of boundary and initial conditions at our disposal and also the variables we want to compute, while keeping additional calculations to a minimum. We obtain the explicit schemes of this meshless method for different possible formulations in finite differences of the problem. Criteria for stability and convergence of the schemes are given for each case. The study of the dispersion of the phase and group velocities presented in previuos paper of the authors is also completed here. We show the application of the propounded schemes to the wave propagation problem and the comparison of the efficiency, convenience and accuracy of the different formulations.
Efficiency and Sustainability Analysis of the Repair and Maintenance Operations of UNS M11917 Magnesium Alloy Parts of the Aeronautical Industry Made by Intermittent Facing
(MDPI, 2021-06-28) Fernández, Jacobo; Rubio Alvir, Eva María; Carou, Diego; Lorente Pedreille, Raquel María; MDPI
This paper analyzes the efficiency and sustainability of facing operations that are required within maintenance operations in the aeronautical industry. Due to the elevated cost and environmental impact of such processes, reducing the operating time while repairing parts is required. In this work, an experimental study of intermittent facing carried out on a magnesium alloy rod was developed. The experiment resembles real repair and maintenance machining operations, where an intermittent facing represents a more realistic scenario and where the results obtained in continuous turning studies are not always applicable. The work was performed with different cooling and lubrication systems and various cutting conditions, also considering the size of the interruption to analyze their impact in the surface roughness. To this end, surface finished in different measuring zones was studied. The aims of the study are to get a better understanding of the intermittent facing process in magnesium alloys typically employed in aeronautical applications and find the most efficient cutting parameters to obtain an improved surface under the safest and most environmentally respectful conditions.
Equivalence of two BV classes of functions in metric spaces, and existence of a Semmes family of curves under a 1-Poincaré inequality
(De Gruyter, 2019-01-30) Durand Cartagena, Estibalitz; Eriksson Bique, Sylvester; Korte, Riikka; Shanmugalingam, Nageswari
We consider two notions of functions of bounded variation in complete metric measure spaces, one due to Martio and the other due to Miranda Jr. We show that these two notions coincide if the measure is doubling and supports a 1-Poincaré inequality. In doing so, we also prove that if the measure is doubling and supports a 1-Poincaré inequality, then the metric space supports a Semmes family of curves structure.
European Robotics Week to introduce robotics and promote engineering
(Wiley, 2018-06-28) Plaza, Pedro; Sancristobal, Elio; Carro, German; García Loro, Félix; Blázquez Merino, Manuel; Castro Gil, Manuel Alonso
We present an activity framed within the European Robotics Week event. Robotics and computational practice are ideal tools for developing science, technology, engineering, and mathematics (STEM) pedagogy. A modular and adaptive hands-on workshop is described in detail. The workshop is based on multiplatform educational robotics content as a first step into the robotics world. Three educational tools are used to introduce examples of robotics applications. The operational details, materials, and examples of activities for selected modules are presented with the expectation that all teachers can adapt these activities to their classes. Despite the small number of students, the experience delivered results that might be useful for other instructors to promote workshops with similar or identical content to generate further benefits. This study demonstrates that it is important to combine theory and practice and include fun tasks that intertwine the challenges of applying theory to problem solving. Furthermore, the results show how the same content can be deployed using three different robotics education tools.
Evaluation of Supply–Demand Adaptation of Photovoltaic–Wind Hybrid Plants Integrated into an Urban Environment
(Wiley, 2019) López-Rey García-Rojas, África; Campinez Romero, Severo; Gil Ortego, Rosario; Colmenar Santos, Antonio
A massive integration of renewable energy sources is imperative to comply with the greenhouse emissions reduction targets fixed to achieve the limitation of global warming. Nevertheless, the present integration levels are still far from the targets. The main reason being the technical barriers arising from their non-manageable features. Photovoltaic and wind sources are the widest spread, as their maturity allows generation with a high-efficiency degree. A deep understanding of facilities’ performance and how they can match the energy demand is mandatory to reduce costs and extend the technical limits and facilitate their penetration. In this paper, we present a novel methodology to evaluate how photovoltaic–wind hybrid facilities, placed in an urban environment can give generation patterns which will be able to match the demand profiles better than facilities installed individually. This methodology has been applied to a broad number of locations spread over the whole planet. The results show that with high homogeneity in terms of site weather characteristics, the hybrid facilities improve the matching up to 15% over photovoltaic plants and up to 35% over wind.
Evolution and Latest Trends in Cooling and Lubrication Techniques for Sustainable Machining: A Systematic Review
(MDPI, 2025-02-05) Polo, Samuel; Rubio Alvir, Eva María; Marín Martín, Marta María; Sáenz de Pipaón, José Manuel; MDPI
This document presents a review on cooling and lubrication methods in machining. A systematic search of information related to these methods was carried out based on the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) methodology. The importance of the sustainability of machining processes is highlighted, as they represent between 10 and 17% of the total manufacturing cost of the final part and have negative environmental and health impacts. Although dry machining completely eliminates the use of cutting fluids, in many cases it produces unsatisfactory results due to the increase in temperature inside the tool, which requires prior analysis to ensure its viability compared to conventional techniques. On the other hand, semi-dry machining, which significantly reduces the volume of cutting fluids, is a more competitive alternative, with results similar to those of conventional machining. Other sustainable cooling and lubrication methods are also being investigated, such as cryogenic and high-pressure cooling, which offer better machining results than conventional processes. However, they have a high initial cost and further research is needed to integrate them into industry. While the combination of these cooling and lubrication methods could lead to improved results, there is a notable lack of comprehensive studies on the subject.

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