Artículos (Ingeniería Aeroespacial y Mecánica de Fluidos)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/11332

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Mapping Circularity Strategies in Building Sustainability Assessment Methods
(Multidisciplinary Digital Publishing Institute(MDPI), 2026-03) Giarma, Christina; Askar, Rand; Trubina, Nika; Salles, Adriana; Lombardi, Patrizia; Karaca, Ferhat; Mateus, Ricardo; Feizollahbeigi, Bahar; Pineda-Martos, Rocío; Bragança, Luís; Ingeniería Aeroespacial y Mecánica de Fluidos
The widespread adoption of circularity principles in the building sector fuels the need for robust and comprehensive evaluation systems, which could benefit from the approaches and indicators employed in widely accepted building sustainability assessment (BSA) methods. Simultaneously, the effective consideration of circular economy (CE) principles into BSA methods becomes increasingly urgent. An important step towards achieving these targets is the investigation of whether, and to which degree, the existing BSA methods encompass and express circularity principles; this study focuses on this relatively underexplored theme. Specifically, this study investigates the degree of association between five widely used BSA methods and the circularity strategies included in the 10R Framework. The methods examined are BREEAM, DGNB, LEED, Level(s) and SBTool (versions and criteria for new buildings). The examination was conducted at the lowest self-contained and score-attributing level of each method and was undertaken by five expert groups—each assigned one method. A quantitative scale from 0 to 5 was used to assess the strength of the association. The results are analysed in terms of (i) the criteria/thematic areas within each method receiving high/low scores, and (ii) the circularity strategies deduced to be strongly/weakly represented in and across the BSA methods. Common trends and milder differences across these axes are observed. Generally, the associations appear stronger in thematic areas relevant to, among others, resources and lifecycle performance, and weaker regarding parameters linked to user comfort. The R-strategies Reduce, Reuse, Recycle and Rethink emerge as more intensely represented in the examined methods. The study’s results indicate areas for further research and potential methodological enhancement.
The spatial structure of jets from steady Taylor cone-jets
(Cambridge University Press, 2025-11) Gañán-Calvo, Alfonso M.; Ingeniería Aeroespacial y Mecánica de Fluidos; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; Agencia Estatal de Investigación. España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); European Union (UE)
This work presents a comprehensive analysis of steady cone-jet electrospray (SCJ-ES) that captures the full range of its steady jet scales within the Taylor-cone electric field. We identify three fundamental regions, each governed by distinct scaling laws and dominant physical mechanisms: (i) the transition region, characterised by the balances that fix the emitted current; (ii) the charge convection-dominated region, where surface charge transport dominates total charge transport and the Taylor field drives jet acceleration; and (iii) the ballistic region, where the jet attains a fixed cylindrical scale before undergoing Rayleigh breakup into charged droplets. This refined theoretical framework harmonises existing models, particularly those using the Taylor–Melcher leaky dielectric model as an electrokinetic approximation for SCJ-ES. Notably, our newly proposed spatial scales achieve a remarkable collapse of published experimental SCJ-ES jet profiles. We also apply this framework to study the charge of resulting droplets using extensive literature data, observing significant differences between weak and strong electrolytes, consistent with recent findings.
The dominant role of jetting in micron- and sub-micron sea spray produced by bubble bursting: A revised model and comparison with measurements
(Elsevier, 2026-01) Gañán-Calvo, Alfonso M.; Herrada Gutiérrez, Miguel Ángel; López-Herrera Sánchez, José María; Ingeniería Aeroespacial y Mecánica de Fluidos; Ministerio de Ciencia e Innovación (MICIN). España; Junta de Andalucía
The size distribution of sub-micron sea spray aerosols (SSA) is a critical component of climate models, yet the primary physical mechanism governing their production – specifically the competition between film and jet droplets from bubble bursting – has remained a subject of intense debate. This work presents a revised, first-principles model to quantitatively resolve this controversy and demonstrate the dominance of jetting for producing micron and sub-micron aerosols. Our approach first rules out the film droplet mechanism as a primary contributor for this size range by demonstrating through physical scaling and numerical simulations that the final average ejected volume of sub-micron droplets is significantly smaller than that from jetting. We then construct a comprehensive global probability distribution function (PDF) for SSA by rigorously modeling its fundamental components in sequence: (i) refining the sub-surface bubble size distribution with a simpler and better experimentally supported exponential law, and (ii) deriving novel scaling laws for the number and size distribution of droplets per bursting event from a large set of high-resolution numerical simulations. A key finding is that the droplet size PDF from a single bubble follows a highly-skewed distribution – optimally modeled by a Generalized Inverse Gaussian distribution – revealing a prolific production of nanometric droplets previously unaccounted for by simpler models. When integrated, these components yield a final predictive model for the global SSA size distribution, with parameters derived directly from physical principles and simulations rather than empirical fitting. The model demonstrates strong predictive consistency, showing close qualitative agreement with a wide corpus of experimental data from both laboratory and oceanic measurements, particularly across the critical 25 nm to 2.5 µm range. By clarifying that jetting is the dominant pathway and providing a robust, physically-grounded predictive tool, this research significantly enhances the fundamental understanding of marine aerosol generation and provides a more accurate foundation for climate and atmospheric chemistry models.
Integrating remote sensing and ion balance to predict yield losses under saline irrigation in rice
(Elsevier, 2026) Egea Cegarra, Gregorio; Rosenbaum, Annkathrin; Becker, Mathias; Quintana-Molina, José Rodolfo; Pariyar, Shyam; Ingeniería Aeroespacial y Mecánica de Fluidos; AGR278: Smart Biosystems Laboratory
Rice cultivation in the Guadalquivir River marshes of southern Spain is increasingly constrained by irrigation water salinity, exacerbated by drought and seawater intrusion. This study assessed the agronomic, physiological, and spectral responses of indica and japonica cultivars under commercial farming conditions across a natural salinity gradient (mean electrical conductivity of irrigation water ranging from 3.1 to 6.9 dS m⁻¹). Field measurements included yield, growth traits, and leaf ion concentrations, complemented with Sentinel-2 vegetation indices and integrated using Generalized Additive Models (GAMs). Rice yield declined steeply with salinity, with up to 70 % losses between 3 and 7 dS m⁻¹ . Rice grown in medium-salinity fields maintained Na/K ratios comparable to low-salinity fields, suggesting that compensatory K⁺ uptake mitigated yield penalties. By contrast, high salinity led to marked ionic imbalance, particularly in japonica cultivars, which consistently exhibited higher Na/K ratios than indica. Spectral data revealed that broad-band greenness indices (NDVI, GNDVI, EVI, SAVI, NDRE) effectively captured early osmotic effects (<60 DAS), while MCARI uniquely detected late-stage ionic stress during reproductive phases. GAM analysis confirmed two phenological windows of higher sensitivity to salinity—vegetative establishment and reproductive development—while demonstrating the predictive utility of combined physiological and spectral indicators (LOOCV R² = 0.867). These findings underscore the need for growth phase-specific management and the potential of integrating physiological and remote sensing data to support adaptation strategies in Mediterranean rice systems.
CircularB-DfC: A decision-support tool for prioritizing building design factors to enhance circular material flows
(Elsevier, 2026-03) Buzatu, Raluca; Askar, Rand; Bompa, Dan; Rajic, Milena; Bas, Bilge; Paoletti, Giulia; Güngör, Bengü; Sertyeşilışık, Pelin; Pineda-Martos, Rocío; Malešev, Mirjana; Ingeniería Aeroespacial y Mecánica de Fluidos; Nazarbayev University
Circularity is increasingly recognised as a critical paradigm for sustainability in the built environment, yet existing efforts to assess it—whether focused on material flow analysis, design-for-disassembly strategies, durability metrics, or carbon accounting—remain fragmented and operate at different scales. Despite numerous indicator sets, the literature lacks an integrated framework that combines both technical design factors and the enabling organisational conditions required to support circular outcomes at the building level. This paper introduces CircularB-DfC (CircularB COST Action – Design for Circularity), a decision-Support Tool with a structured matrix for prioritising building design factors to enhance circular material flows. The framework consolidates insights from a systematic literature review and a multi-stage expert engagement process, resulting in 35 technical indicators and 20 enabling factors. These are organised into four technical categories: Material Selection; Design for Disassembly; Embodied Energy and Carbon Footprint; Waste Minimisation, and one enabling category, Circular Construction Management, including Governance, Certification, Stakeholder Engagement, Digitalisation, and Socio-economic aspects. Indicators and enablers are aggregated into a Design Score and an Enabler Score to support early decision-making. The tool was applied to three illustrative scenarios: a reinforced-concrete industrial hall in the Western Balkans, a steel office building in Central Europe, and a timber residential project in East London. The steel scenario achieved the highest Design and Enabler Scores, the concrete scenario performed strongest in Waste Minimisation through prefabrication and site-based strategies, and the timber scenario scored lowest overall due to limited reuse and disassembly provisions in the original design. While CircularB-DfC offers a simple and transparent basis for integrating circularity in design, it is limited by the subjectivity of expert-based weighting and its static structure. Future research will focus on dynamic modelling, integration with digital tools, and broader validation to enhance applicability.
A Global Compendium of Nature-based Solutions in Small-Medium Islands
(Springer Nature, 2026) Mansoldo, Mark D.C.; Serra, Elisa; Igondová, Erika; Moustakas, Aristides; Dönmez, Abdullah Hüseyin; Tsatsou, Alexandra; Kumuk, Berre; Zoumides, Christos; Tzirkalli, Elli; Pineda-Martos, Rocío; Ingeniería Aeroespacial y Mecánica de Fluidos; European Union
Small and medium-sized islands (SMI) combine high ecological value with limited resources and vulnerability to climatic and environmental risks. Nature-based solutions (NbS) can contribute to addressing some of these challenges, but studies on the uptake and effectiveness of NbS in SMI remain scattered, with few systematic syntheses. Here, we introduce the SMI-NbS compendium, a comprehensive and open-access dataset compiling 280 NbS case studies implemented across SMI worldwide, developed through a systematic review of published and grey literature. Each SMI-NbS case study includes information on the location, NbS category, ecosystem types, societal challenges addressed, associated co-benefits, and links to the United Nations’ Sustainable Development Goals (SDGs). The SMI-NbS compendium provides practical information on NbS implementation and identifies current research trends and gaps, such as the dominance of ecological and climate-focused NbS, with limited integration of other socio-economic challenges, thereby supporting further research and enabling knowledge exchange across the science-policy-practice interface to inform sustainable development pathways in SMI.
Volatile organic compounds, SO2 and NO2 capture by means of an indoor active living wall
(Elsevier, 2026-04-15) Fernández Espinosa, Antonio José; Montiel de la Cruz, J.M.; Fernández Cañero, Rafael; Pérez Urrestarazu, Luis; Rossini Oliva, Sabina; Química Analítica; Agronomía; Ingeniería Aeroespacial y Mecánica de Fluidos; Biología Vegetal y Ecología; Junta de Andalucía
The ability of an active living wall (ALW) to capture indoor air pollutants was studied. Five different species (Spathiphyllum wallisii, Tradescantia zebrina, Philodendron scandens, Ficus pumila and Chlorophytum comosum) were assessed. The experiments were performed inside a closed glass chamber for each species separately. Gas pol lutants (NO2 and SO2) and volatile organic compounds (formaldehyde, acetone, n-hexane and n-heptane) were introduced into the chamber monitoring concentration changes. High values of the Pollutant Reduction (PR%) indicator were recorded after releasing pollutants in the chamber, especially for CH2O and SO2. After 24 h, PR% in the chamber ranged 96-98% for all the plant species studied. The ALW was more efficient in removing CH2O and NO2 than other air contaminants. In addition, differences in Differential Reduction Efficiency (DRE%) in dicator were observed among plant species depending on the pollutant considered. After 15 min from the in jection of TVOCs, a reduction of 24-40% was achieved with all plant species but S. wallisii showed greater DRE for NO2, with 60% reduction in the first hour of exposure. The presented data demonstrates the effectiveness of active living wall systems for improving indoor air quality
Magnetic Field Simulation and Correlated Low-Frequency Noise Subtraction for an in-Orbit Demonstrator of Magnetic Measurements
(Institute of Electrical and Electronics Engineers (IEEE), 2024-10) María-Moreno, Cristian; Mateos, Ignacio; Pacheco Ramos, Guillermo; Rivas, Francisco; Cifredo-Chacón, María-Ángeles; Quirós Olozábal, Ángel; Guerrero Rodríguez, José María; Karnesis, Nikolaos; Ingeniería Aeroespacial y Mecánica de Fluidos; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER); Junta de Andalucía; Universidad de Cádiz; European Union
In recent years, nanosatellites have revolutionized the space sector due to their significant economic and time-saving advantages. As a result, they have fostered the testing of advanced instruments intended for larger space science missions. The case of the Magnetic Experiment for the Laser Interferometer Space Antenna (MELISA) is presented in this work. MELISA is a magnetic measurement instrument which aims at demonstrating the in-orbit performance of anisotropic magnetoresistance (AMR) sensors featuring dedicated noise reduction techniques at sub-millihertz frequencies. Such low frequency ranges are relevant for future space-borne gravitational wave (GW) detectors, where the local magnetic environment of the satellite might yield a significant contribution to the overall noise budget of the observatory. The demanding magnetic noise levels required for this bandwidth, down to 0.1 mHz, make measurements arduous. To explore sensing solutions within the H2020 European Commission Programme with the involvement of the European Space Agency (ESA), the functional performance of MELISA-III will be validated in-orbit. During operations, there is the possibility to measure the low-frequency magnetic contribution stemming from orbiting the Earth’s magnetic field, which will impede the characterization of the intrinsic performance of the sensor. With the objective of minimizing excess noise during the in-flight operations, the present research aims to simulate the environmental magnetic conditions in low Earth orbit (LEO) in order to identify and subtract undesired contributions to the measurements. The in-orbit long-term magnetic fluctuations are replicated using a triaxial Helmholtz coil system. A fluxgate magnetometer (FGM) allows the correlation of the generated field with the payload measurements, leading to the subsequent subtraction. Proving the effect of this approach will facilitate the noise characterization of magnetic sensors in LEO, paving the way for the in-orbit validation of MELISA-III for use in magnetically demanding missions with long integration times.
Optimal planning and tracking for E-sail transition between steady-states
(Elsevier, 2025-03) Pacheco Ramos, Guillermo; Vázquez Valenzuela, Rafael; García Vallejo, Daniel; Ingeniería Aeroespacial y Mecánica de Fluidos; Ingeniería Mecánica y Fabricación; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER)
The E-sail technology employs the repulsive force of solar wind protons on positively charged tethers for continuous propulsion. Mission research highlights the necessity to modulate thrust, while dynamics studies reveal a tendency for oscillation. This study explores achieving stable transitions between different E-sail steady-states, each associated to varying voltages and thrust levels. By creating a simplified multibody model with straight, rigid tethers, controlled transitions are investigated, considering the system's underactuated nature. An optimal control perspective is adopted to minimize a cost function for optimal planning. Additionally, the system's response to open-loop control actions is examined, underscoring the need for feedback to ensure precise trajectory tracking. Consequently, a procedure for deriving a feedback control law using Model Predictive Control is proposed. The results suggest the feasibility of stable transitions using underactuated control and advocate for applying these methods to more complex and realistic scenarios.
The role of waves and heat exchange in the hydrodynamics of multi‐basin bays: the example of Cádiz bay (Southern Spain)
(Wiley, 2021) Zarzuelo Romero, Carmen; López-Ruiz, Alejandro; Ortega Sánchez, M.; Ingeniería Aeroespacial y Mecánica de Fluidos; Ministerio de Economía y Competitividad (MINECO). España
Multi-basin bays constitute one of the most complex coastal environments, as tides,waves, freshwater discharges and air-water heat exchange often coexist in basins with very differentcharacteristics, ranging from low-friction open water bodies directly connected to the open sea tonarrow, highly frictional shallow creek systems with no connection to the open sea. Although theinfluence of tides and baroclinic gradients in these areas is relatively well known, the role of waves in thehydrodynamics and distributions of density, salinity and temperature has received less attention. The aimof this research is to evaluate the effects of waves and heat exchange on the hydrodynamics of multiplebasins through numerical modeling. The model is calibrated and tested in a mesotidal bay in SouthernSpain with five different basins; the results are used to analyze the momentum balance equation and thesalinity, temperature and density distributions for simulations with and without consideration of waves.The results show that baroclinic density gradients often dominate the hydrodynamics in highly frictional,shallow basins of the bay where the air-water heat exchange is more efficient. Waves can also modifythe hydrodynamics of basins directly connected to open sea by increasing flow velocities and causingdeviations of baroclinic density gradients, increasing the importance of tidal stresses in low frictionalbasins, while increasing baroclinic density gradients in narrow, highly frictional basins.
Probabilistic aircraft trajectory prediction in cruise flight considering ensemble wind forecasts
(Elsevier, 2018-11) Franco Espín, Antonio; Rivas Rivas, Damián; Vázquez Valenzuela, Rafael; Ingeniería Aeroespacial y Mecánica de Fluidos; Ministerio de Economia, Industria y Competitividad (MINECO). España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER)
The problem of aircraft trajectory prediction subject to wind uncertainty is addressed. In particular, a probabilistic analysis of aircraft flight time and fuel consumption in cruise flight is presented. The wind uncertainty is obtained from ensemble weather forecasts. The cruise is composed of a given number of segments subject to uncertain winds (both along-track winds and crosswinds). The resulting average ground speed of each segment is modeled as a random variable, assuming a Log-Normal distribution. The probabilistic trajectory predictor developed is based on the Probabilistic Transformation Method; the input is the probability density functions of the average ground speeds of the cruise segments, and the output is the probability density functions of the flight time and the fuel consumption. Results are presented for several aircraft of different categories (medium and heavy), for a given trans-oceanic route and a real ensemble weather forecast. The effects of wind uncertainty on flight predictability and on fuel loading are analyzed. A fuel penalty parameter is defined, and the cost of flight unpredictability is quantified. The sample variability of all the results has been quantified by means of standard errors.
Stochastic analysis of fuel consumption in aircraft cruise subject to along-track wind uncertainty
(Elsevier, 2017-07) Vázquez Valenzuela, Rafael; Rivas Rivas, Damián; Franco Espín, Antonio; Ingeniería Aeroespacial y Mecánica de Fluidos; Ministerio de Economia, Industria y Competitividad (MINECO). España; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER)
The effects of along-track wind uncertainty on aircraft fuel consumption are analyzed. The case of cruise flight subject to an average constant wind is considered. The average wind is modeled as a random variable, which in this paper is assumed to follow either a uniform or a beta distribution. The probability density function (pdf) of the fuel consumption is obtained using a numerical approach that is based on the Probability Transformation Method (a method that evolves the wind pdf). The dynamics of aircraft mass evolution in cruise flight is defined by a simple nonlinear equation that can be solved analytically; this exact solution is used to assess the accuracy of the method. A general analysis is performed for arbitrary along-track winds. Comparison of the numerical results with the exact analytical solution shows an excellent agreement in all cases. A linear approximation is analyzed as well, which turns out to be very accurate for this problem. The results show that the standard deviation of the fuel mass distribution varies almost linearly with the standard deviation of the wind, whereas the mean of the fuel mass is practically independent of the wind uncertainty. They also show that, for the same along-track wind uncertainty, the uncertainty in the fuel consumption is larger in the case of headwinds than in the case of tailwinds.
Nutrients' distribution during fertigation of a felt-based living wall
(Springer, 2023) Suárez Cáceres, Gina Patricia; Recena Garrido, Ramiro; García López, Ana M.; Delgado García, Antonio; Pérez Urrestarazu, Luis; Agronomía; Ingeniería Aeroespacial y Mecánica de Fluidos
The lack of space in cities has favoured the development of vertical gardens in indoor and outdoor environments. For an adequate development and appearance of the plants in these living walls, it is necessary to provide nutrients (usually by means of fertigation). One of the main limitations is the difficulty in obtaining a uniform distribution of nutrients, especially in felt systems. The objective of this research was to identify whether the distribution of nutrients (particularly iron and phosphorous) applied by fertigation in a felt living wall depended on the species used and the location of the plants in height. Three modules of a Fytotextile® felt-based living wall were used, each module containing three columns of different species: Soleirolia soleirolii, Philodendron hederaceum, and Nephrolepis exaltata. Fertigation was applied using a Hoagland–Arnon solution for 4 months. Measurements of leaf area, normalised difference vegetation index (NDVI), chlorophyll meter readings (CMR), fresh and dry weight, and P and Fe concentration were carried out for each of the plants. Comparing variables within the same species at different heights showed no significant differences in the variables. This means that the distribution of nutrients along the living wall (especially in height) was uniform. It is important to note that these results could vary for other types of living walls or for other configurations of the fertigation system.
Establishment and development of ornamental grasses on green roofs and living walls
(Springer, 2023) Suárez Cáceres, Gina Patricia; Mejía-Sampedro, Diana Karen; Fernández Cañero, Rafael; Loges, Vivian; Pérez Urrestarazu, Luis; Agronomía; Ingeniería Aeroespacial y Mecánica de Fluidos
Ornamental grasses are often used in gardens to improve biodiversity and as additional aesthetical resources. However, their use in green roofs (GR) and living walls (LW) is not so widespread and it has not been studied extensively. The aim of this work is to assess the performance of seven grass species (Imperata cylindrica ‘Red Baron’, Acorus gramineus, Stipa tenuis sima ‘Pony Fails’, Carex flagellifera ‘Bronzita’, Carex oshimensis ‘Evergold’, Uncinia rubra ‘Everflame’ and Miscanthus sinensis) for their use in GR and LW. The growth of the plants was evaluated (i.e. biomass production, dimensions), as well as their visual quality and survival. C. flagellifera and C. oshimensis showed coverage levels greater than 75% and good visual quality, while A. gramineus reached 55–60%. I. cylindrica and M. sinensis showed coverages slightly below 50% in the LW, however, both performed well in the GR, though with a lower visual quality. U. rubra did not develop well, reaching the lowest coverage (below 45%) but maintaining a high visual quality. S. tenuissima also attained low coverage in the LW and presented high mortality, especially in the GR. In LW, C. oshimensis stood out in flowering, while S. tenuissima showed the highest flowering rate in GR. The species should be selected considering their characteristics and performance in order to achieve a correct appearance and development. Interspecific interactions are especially important in LW, as species with upward growth should be placed above species with fallen leaves, not below.
Removal of volatile organic compounds by means of a felt-based living wall using different plant species
(MDPI, 2021) Suárez Cáceres, Gina Patricia; Pérez Urrestarazu, Luis; Agronomía; Ingeniería Aeroespacial y Mecánica de Fluidos
Poor indoor quality affects people’s health and well-being. Phytoremediation is one way in which this problem can be tackled, with living walls being a viable option for places with limited space. The aim of this study was to evaluate the efficiency of five plant species in a living wall to remove Volatile Organic Compounds (VOCs) and to identify whether the type of pollutant has any influence. An enclosed chamber was used to add the contaminants n-hexane and formaldehyde independently. Total VOCs were measured for three days in two scenarios: (1) empty chamber, and (2) chamber with living wall. Five living walls were prepared, each with three plants of the same species: Spathiphyllum wallisii, Philodendron hederaceum, Ficus pumila, Tradescantia pallida, and Chlorophytum comosum. There was no correlation between leaf area/fresh weight/dry weight and the contaminant reduction. In general, all five species were more efficient in reducing TVOCs when exposed to formaldehyde than to n-hexane. Chlorophytum comosum was the most efficient species in reducing the concentration of TVOCs for both contaminants, Spathiphyllum wallisii being the least efficient by far.
WEFE nexus unveiled: a comprehensive review of monitoring and modelling methods in the water-energy-food-ecosystems nexus
(IOP Publishing, 2025-10) Vrachioli, Maria; Mellios, Nikos; Alp, Emre; Borchard, Nils; Sousa Coutinho Calheiros, Cristina; Pineda-Martos, Rocío; Laspidou, Chrysi; Ingeniería Aeroespacial y Mecánica de Fluidos; European Cooperation in Science and Technology (COST); European Union (UE)
Sustainable resource management in the face of climate change is a pressing challenge for our society. This paper delves into the water-energy-food-ecosystems (WEFE) nexus, a scientific framework that supports the integrated assessment and management of the interconnected resources. Shifting from sectoral to cross-sectoral and transdisciplinary perspectives, the WEFE nexus addresses interdependencies and interactions among water, energy, food, ecosystems, and climate. This paper focuses on the extended nexus, incorporating ecosystems as a fourth pillar, underscoring the importance of considering ecosystems on an equal footing with water, energy, and food sectors. In addition, the paper emphasizes the significance of monitoring and modelling techniques, laying the foundations for understanding the nexus complexities and assessing uncertainty. The paper offers an overview of integrated nexus modelling, system analysis and socio-economic modelling, bridging the gap between nexus science and practice. It highlights the role of multifaceted stakeholder engagement methods, policy assessment, and institutional analysis in nexus models. Quantifying the nexus through indicators, and its alignment with the Sustainable Development Goals, EU Green Deal, and EU Blue Deal are also key focal points. Finally, the last part of the paper addresses challenges in existing nexus modelling attempts, advocates for the integration of transdisciplinary information, and presents lessons learned. The paper concludes with recommendations for the future of the WEFE nexus, emphasizing its potential in fostering transformative change toward sustainable resource management and inclusive policymaking.
Event-triggered boundary estimation for 2 × 2 hyperbolic PDEs with disturbance
(Elsevier, 2026) Zhao, Yan; Vázquez Valenzuela, Rafael; Ingeniería Aeroespacial y Mecánica de Fluidos; Ministerio de Ciencia, Innovación y Universidades (MICIU). España
This paper addresses the event-triggered boundary estimation problem for 2 × 2 linear hyperbolic partial differential equations (PDEs) subject to disturbances. These disturbances enter the PDEs through the boundary and are represented as an ordinary differential equation (ODE). The scenario considered involves transmitting boundary measurements to the observer only when necessary, as determined by a dynamic event-triggering condition. This approach aims to conserve communication and computational resources. The event-triggered observer is designed using the backstepping method, and an event-triggering condition is proposed to determine the time instants when sampled measurements should be transmitted. Under this event-triggered estimation mechanism, a minimal dwell-time between consecutive triggering time instants is guaranteed. Furthermore, the well-posedness of the solutions and the exponential convergence of the estimation error are ensured. Finally, the obtained results are applied to the Saint-Venant equations to demonstrate the effectiveness of the event-triggered estimation method.
Backstepping for partial differential equations: A survey
(Elsevier, 2026) Vázquez Valenzuela, Rafael; Auriol, Jean; Bribiesca Argomedo, Federico; Krstic, Miroslav; Ingeniería Aeroespacial y Mecánica de Fluidos; Ministerio de Ciencia, Innovación y Universidades (MICIU). España
Systems modeled by partial differential equations (PDEs) are at least as ubiquitous as those by nature finite-dimensional and modeled by ordinary differential equations (ODEs). And yet, systematic and readily usable methodologies, for such a significant portion of real systems, have been historically scarce. Around the year 2000, the backstepping approach to PDE control began to offer not only a less abstract alternative to PDE control techniques replicating optimal and spectrum assignment techniques of the 1960s, but also enabled the methodologies of adaptive and nonlinear control, matured in the 1980s and 1990s, to be extended from ODEs to PDEs, allowing feedback synthesis for systems that are uncertain, nonlinear, and infinite-dimensional. The PDE backstepping literature has since grown to hundreds of papers and nearly a dozen books. This survey aims to facilitate the entry into this thriving area of overwhelming size and topical diversity. Designs of controllers and observers, for parabolic, hyperbolic, and other classes of PDEs, in one or more dimensions, with nonlinear, adaptive, sampled-data, and event-triggered extensions, are covered in the survey. The lifeblood of control are technology and physics. The survey places a particular emphasis on applications that have motivated the development of the theory and which have benefited from the theory and designs: flows, flexible structures, materials, thermal and chemically reacting dynamics, energy (from oil drilling to batteries and magnetic confinement fusion), and vehicles.
Approach to similarity in the pinch-off of a viscous liquid thread
(Cambridge University Press, 2025) Corpart, Marie; Herrada Gutiérrez, Miguel Ángel; Deblais, Antoine; Bonn, Daniel; Ingeniería Aeroespacial y Mecánica de Fluidos; Ministerio de Economia, Industria y Competitividad (MINECO). España
The breakup of viscous liquid threads is governed by a complex interplay of inertial, viscous and capillary stresses. Theoretical predictions near the point of breakup suggest the emergence of a finite-time singularity, leading to universal power laws describing the breakup, characterised by a universal prefactor. Recent stability analyses indicate that, due to the presence of complex eigenvalues, achieving similarity may only be possible through time-damped oscillations, making it unclear when and how self-similar regimes are reached for both visco-inertial and viscous regimes. In this paper, we combine experiments with unprecedented spatio-temporal resolution and highly resolved numerical simulations to investigate the evolution of the liquid free surface during the pinching of a viscous capillary bridge. We experimentally show for the first time that, for viscous fluids the approach to the self-similar solution is composed of a large overshoot of the instantaneous shrinking speed before the system converges to the nonlinear pinch-off similarity solution. In the visco-inertial case, the convergence to the stable solution is oscillatory, whereas in the viscous case, the approach to singularity is monotonic. While our experimental and numerical results are in good agreement in the viscous regime, systematic differences emerge in the visco-inertial regime, potentially because of effects such as polymer polydispersity, which are not incorporated into our numerical model.
Feasibility of an aquaponic system composed of a living wall coupled with an ornamental pond with fish in real-life conditions
(Wiley-VCH, 2025) Fernández Cabanás, Víctor Manuel; Martínez Millán, Leonardo; Suárez Cáceres, Gina Patricia; Fernández Cañero, Rafael; Rossini Oliva, Sabina; Fernández Espinosa, Antonio José; Franco Salas, Antonio; Pérez Urrestarazu, Luis; Agronomía; Biología Vegetal y Ecología; Ingeniería Aeroespacial y Mecánica de Fluidos; Química Analítica; Junta de Andalucía
Green and blue infrastructures are often combined to create pleasant urban landscapes and provide new ecosystems in the built environment. New techniques for building integrated vegetation systems, such as vertical greening, are becoming common. In this work, we evaluate a case study of a combined aquaponic system composed of a living wall (LW) coupled to an ornamental pond with fish. The system allows the metabolic waste of fish and the unconsumed feed to be converted by a bacterial population into mineral nutrients that are used by the plants in the LW. For this purpose, the pond water was recirculated through a 7.2 m2 LW planted with 11 different ornamental plant species. The objectives of the study were (1) assessing the performance of LW vegetation irrigated with water from a pond and (2) monitoring the pond water quality with the LW used as a biofilter. The evolution of vegetation growth was monitored for 1 year by image analysis, and the concentration of some nutrients in the water was determined pre- and post-coupling. Vegetation cover increased from 30% to almost 100% after 1 year. Iron, magnesium, and nitrogen content increased in the LW plants after coupling with the pond. Electrical conductivity increased slightly with time, keeping below 500 µS cm−1. Nitrates, nitrites, and phosphates in the water were significantly reduced after the pond was coupled with the LW. Overall, the combination of both systems proved to be successful, optimizing the use of water and fertilizers with a circular economy focus.

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