Artículos (Ingeniería Aeroespacial y Mecánica de Fluidos)

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

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End-of-life of renewable energy technologies in urban environments. A state-of-the-art on installation trends, materials, and best practices in the EU
(2025-10) De Simone, Marilena; Campagna, Daniele; Cabeza, Luisa F.; Pineda-Martos, Rocío; Santos, Paulo; Turk, Janez; Ungureanu, Viorel; Zsembinszki, Gabriel; Ingeniería Aeroespacial y Mecánica de Fluidos; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España; European Union
The European Commission is promoting the production of thermal energy and electricity from renewable sources, coupled with storage systems, to decarbonize the built environment. However, these technologies use prevalently virgin raw materials, and end-of-life (EoL) circular frameworks are still difficult to be implemented due to technical, regulatory, and market barriers. This paper aims to present a state-of-the-art on the trends in installation, materials, EoL strategies, and companies active in renewable energy systems recycling. Solar, wind, and geothermal sources are examples of technologies easily incorporated into cities. The purpose is to provide information to stakeholders that should design technical solutions according to circularity criteria. The information, from both scientific and grey literature, showed that solar technologies represent the most widespread type of systems, with a considerable number of best practices and companies specialized in recycling. Wind technology follows in installation trends and activity of reuse-oriented companies. Geothermal, on the other hand, offers a reduced number of reference examples. Furthermore, this review provides an overview of the installation and potential EoL scenarios of electrical and thermal energy storage systems, highlighting significant differences in the implementation of circularity strategies. The study closes with considerations and suggestions for practical applications.
Relative Estimation and Control for Loyal Wingman MUM-T
(Multidisciplinary Digital Publishing Institute (MDPI), 2025) Martín Sánchez, Jesús; Esteban Roncero, Sergio; Ingeniería Aeroespacial y Mecánica de Fluidos; TEP945: Ingeniería Aeroespacial
The gradual integration of Manned–Unmanned Teaming (MUM-T) is gaining increasing significance. An intriguing feature is the ability to do relative estimation solely through the use of the INS/GPS system. However, in certain environments, such as GNSS-denied areas, this method may lack the necessary accuracy and reliability to successfully execute autonomous formation flight. In order to achieve autonomous formation flight, we are conducting an initial investigation into the development of a relative estimator and control laws for MUM-T. Our proposal involves the use of a quaternion-based relative state estimator to combine GPS and INS sensor data from each UAV with vision pose estimation of the remote carrier obtained from the fighter. The technique has been validated through simulated findings, which paved the way for the experiments explained in the paper.
ROS-Based Multi-Domain Swarm Framework for Fast Prototyping
(Multidisciplinary Digital Publishing Institute (MDPI), 2025) Martín Sánchez, Jesús; Esteban Roncero, Sergio; Ingeniería Aeroespacial y Mecánica de Fluidos; TEP945: Ingeniería Aeroespacial
The integration of diverse robotic platforms with varying payload capacities is a critical challenge in swarm robotics and autonomous systems. This paper presents a robust, modular framework designed to manage and coordinate heterogeneous swarms of autonomous vehicles, including terrestrial, aerial, and aquatic platforms. Built on the Robot Operating System (ROS) and integrated with C++ and ArduPilot, the framework enables real-time communication, autonomous decision-making, and mission execution across multi-domain environments. Its modular design supports seamless scalability and interoperability, making it adaptable to a wide range of applications. The proposed framework was evaluated through simulations and real-world experiments, demonstrating its capabilities in collision avoidance, dynamic mission planning, and autonomous target reallocation. Experimental results highlight the framework’s robustness in managing UAV swarms, achieving 100% collision avoidance success and significant operator workload reduction, in the tested scenarios. These findings underscore the framework’s potential for practical deployment in applications such as disaster response, reconnaissance, and search-and-rescue operations. This research advances the field of swarm robotics by offering a scalable and adaptable solution for managing heterogeneous autonomous systems in complex environments.
Segmented Analysis for the Performance Optimization of a Tilt-Rotor RPAS: ProVANT-EMERGENTIa Project
(Multidisciplinary Digital Publishing Institute (MDPI), 2025-07) Martínez Blanco, Álvaro; Franco Espín, Antonio; Esteban Roncero, Sergio; Ingeniería Aeroespacial y Mecánica de Fluidos; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; TEP945: Ingeniería Aeroespacial
This paper aims to analyze the performance of a tilt-rotor fixed-wing RPAS (Remotely Piloted Aircraft System) using a segmented approach, focusing on a nominal mission for SAR (Search and Rescue) applications. The study employs optimization techniques tailored to each segment to meet power consumption requirements, and the results highlight the accuracy of the physical characterization, which incorporates nonlinear propulsive and aerodynamic models derived from wind tunnel test campaigns. Critical segments for this nominal mission, such as the vertical take off or the transition from vertical to horizontal flight regimes, are addressed to fully understand the performance response of the aircraft. The proposed framework integrates experimental models into trajectory optimization procedures for each segment, enabling a realistic and modular analysis of energy use and aerodynamic performance. This approach provides valuable insights for both flight control design and future sizing iterations of convertible UAVs (Uncrewed Aerial Vehicles).
Monitoring intertidal ecosystems: Assessing spatio–temporal variability with Sentinel-2 and Landsat 8
(Elsevier, 2025) Zarzuelo Romero, Carmen; López-Ruiz, Alejandro; Bermúdez, María; Ortega-Sánchez, Miguel; Caballero, Isabel; Ingeniería Aeroespacial y Mecánica de Fluidos; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; European Union (UE)
Intertidal zones are home to critical ecosystems that provide a wide range of ecological, social and economic benefits, but are increasingly vulnerable to climate change and anthropogenic pressures. This study aims to develop a robust methodology for mapping and analysing these areas using satellite imagery, focusing on the creation of a new spectral index specifically designed for zoning marsh ecosystems. The methodology involves selecting optimal satellite data, correcting for solar reflectance, identifying intertidal pixels using the Normalised Difference Water Index (NDWI) and classifying these zones into categories such as seagrass beds, mudflats, low marsh and high marsh. By comparing the effectiveness of Sentinel-2 and Landsat 8 datasets, the research addresses common challenges in land cover mapping of intertidal environments — such as cloud cover, reflectance variability and tidal influences. The Bay of Cádiz (south-west Spain), with its extensive intertidal areas characterised by diverse habitats such as mudflats, marshes and seagrass beds, serves as an ideal case study for understanding coastal dynamics driven by tidal cycles. The results highlight the usefulness of the proposed spectral index in assessing changes in intertidal habitats over time, achieving classification accuracies of up to 93.6%, and supporting long-term monitoring efforts that are crucial for coastal conservation strategies. By refining intertidal mapping techniques and improving the detection of specific land cover classes, this research addresses existing methodological gaps and provides valuable insights for local coastal management. In future work, the methodology could be adapted to other intertidal systems and integrated with additional data sources to simulate future scenarios under sea level rise or extreme events. These improvements will help guide effective, data-driven strategies for conserving intertidal ecosystems in the face of accelerating environmental change.
Dermal Exposure of Operators, Bystanders and Residents Derived from Unmanned Aerial Spraying Systems (UASS) in Vineyard
(Multidisciplinary Digital Publishing Institute (MDPI), 2025) Sánchez-Fernández, Luis; Díaz García, Francisco; Pérez Ruiz, Manuel; Sandin España, Pilar; Alonso Prados, José Luis; Mateo Miranda, Miguelina; Martínez Guanter, Jorge; García Montero, Esther; Márquez, María del Carmen; Abril Muñoz, Isaac; Ingeniería Aeroespacial y Mecánica de Fluidos; European Agricultural Fund for Rural Development (EAFRD)
The increasing adoption of unmanned aerial spraying services presents a transformative opportunity for precision agriculture, enabling targeted and efficient application of plant protection products. However, ensuring their safe and regulated integration into European farming requires a comprehensive understanding of exposure risks for operators, bystanders, and residents. Expanding scientific knowledge in this domain is crucial for establishing a dedicated risk assessment framework for unmanned aerial spraying applications. This study evaluates dermal exposure levels among operators, residents, and bystanders, comparing unmanned aerial spraying applications with conventional vehicle-based and manual handheld spraying methods based on existing risk assessment and exposure models. Results suggest that unmanned aerial sprayers reduce dermal exposure for pilots, residents, and bystanders due to their remote operation and reduced drift compared to conventional spraying methods. However, critical exposure points arise during mixing, loading, and auxiliary tasks, where dermal exposure levels exceed model estimates. These elevated exposure levels are attributed to the higher frequency and concentrated handling of plant protection products in unmanned aerial spraying operations compared to traditional spraying methods. These findings highlight the need for targeted risk mitigation strategies to enhance operator safety, such as implementing closed transfer systems, optimized handling protocols, and specialized protective equipment.
Short-term space occupancy and conjunction filter
(Elsevier, 2025) Sánchez Rivero, Ana; Bombardelli, Claudio; Vázquez Valenzuela, Rafael; Ingeniería Aeroespacial y Mecánica de Fluidos; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; Ministerio de Economia, Industria y Competitividad (MINECO). España; European Union (UE)
Conjunction analysis (CA) for resident space objects (RSOs) is essential for preventing collisions in an increasingly crowded orbital environment and preserving the operational integrity of satellites. A first and fundamental step in the CA process is to estimate the range of altitudes that each object can occupy throughout an operational screening time of, typically, a few days. In this paper, a method is proposed to analytically evaluate such range of altitudes in a zonal problem model and for a time horizon of generic duration thereby generalizing the concept of space occupancy (SO) introduced in a recent work. The proposed method is exploited to construct a new conjunction filter that considerably improves the classical apogee-perigee filter routinely employed in CA. The effectiveness of the new filter is assessed in a low-Earth orbit (LEO) scenario using a high-fidelity perturbation model across a broad spectrum of orbits and conjunction geometries.
A note on the thrust of airfoils
(Cambridge University Press, 2025) Gordillo Arias de Saavedra, José Manuel; Ingeniería Aeroespacial y Mecánica de Fluidos; TEP103: Mecánica de Fluidos
Here, we show that the thrust force of oscillating airfoils calculated within the linearised potential flow approach by means of the vortex impulse theory coincides with the one resulting from the integration of the unsteady pressure distribution around the solid obtained by Garrick (1936) when the vertical component of the wake velocity is calculated self-consistently and the analysis retains the contribution of the flux of horizontal momentum induced by the starting vortex. The limitations of the self-consistent linearised potential flow approach for predicting the thrust force of airfoils oscillating periodically with small amplitudes but large values of the reduced frequency are also discussed, as well as the reasons behind the ability of other results in the literature to approximate measurements better than Garrick’s theory. In fact, for those cases in which the airfoil oscillates periodically, the flux of horizontal momentum induced by the starting vortex is negligible and the vortices in the wake are convected parallel to the free-stream velocity, we have deduced an equation for the mean thrust coefficient which differs from previously published results and is in agreement with experimental and numerical results. In addition, for those cases in which the airfoil is suddenly set into motion, we have also deduced an equation that retains the effect of the starting vortex and correctly quantifies the transient thrust force.
Stability of finite-length collapsible channel flow to spanwise perturbations
(AIP Publishing, 2024-12) González Herrer, Emiliano; Herrada Gutiérrez, Miguel Ángel; Gañán-Calvo, Alfonso M.; Stewart, Peter S.; Ingeniería Aeroespacial y Mecánica de Fluidos; Ministerio de Ciencia e Innovación (MICIN). España; Engineering and Physical Sciences Research Council (UK); TEP219: Física de Fluidos y Microfluídica
We consider flow through a finite-length flexible-walled channel formed by removing a portion from one wall of a wide rigid channel and replacing by a pre-tensioned hyperelastic sheet of finite thickness. The flow is driven by a prescribed upstream flow rate which is uniform along the channel inlet, and so with periodic boundary conditions in the transverse direction the system admits a steady state with a wall profile which is deformed in the streamwise direction but spatially uniform in the spanwise direction. Identical to the planar case, this system exhibits two stable static configurations: an upper branch where the flexible wall is mostly inflated and a lower branch where the wall is highly collapsed. We consider the stability of these steady states to spanwise perturbations, showing that both can become unstable to distinct families of self-excited oscillations. In particular, for large spanwise wavenumbers, these steady states are unstable to oscillatory normal modes where the perturbation wall profile has a single oscillating hump in the streamwise direction, not previously seen in collapsible channel flows driven by fixed upstream flux. Furthermore, for sufficiently large wavenumbers and no wall pre-tension in the spanwise direction, this system is always unstable to a new spanwise non-uniform static configuration, which arises due to the merging of a pair of unstable oscillatory normal modes. However, with non-zero spanwise wall pre-tension, there is always a region of parameter space where the spanwise uniform steady state is stable for all wavenumbers.
Beyond Macronutrients Supply: The Effect of Bio-Based Fertilizers on Iron and Zinc Biofortification of Crops
(MDPI, 2025) Nieto Cantero, Juan; García López, Ana M.; Recena Garrido, Ramiro; Quintero Ariza, José Manuel; Delgado García, Antonio; Agronomía; Ingeniería Aeroespacial y Mecánica de Fluidos
Iron (Fe) and Zinc (Zn) deficiencies in crops pose indirect problems for human health. The risk of these deficiencies increases with high doses of phosphate fertilizers. Fertilizers obtained through recycling—so-called bio-based fertilizers (BBFs)—can contain significant amounts of Fe and Zn, which can contribute to crop biofortification. Although the use of some organic BBFs has been shown to improve biofortification, an in-depth study on this effect and on the effect of P on Fe and Zn nutrition with the use of different kinds of bio-based P fertilizers is still lacking. A pot experiment with 11 different BBFs was conducted using two soils with different physicochemical properties that affect P, Fe, and Zn dynamics (one rich in CaCO3 and the other rich in Fe oxides) to assess their biofortification effects on wheat and sunflower. Although some BBFs increased Fe concentration in the edible parts, the overall trend was towards an increased P:Fe ratio (up to 62%), which decreased Fe digestibility. On the other hand, all BBFs led to Zn biofortification, with a 27% decrease in the P:Zn ratio in the CaCO3-rich soil, while in the Fe oxide-rich soil, the decrease was up to 61%. The supply of Zn and organic C, as well as the dominant P forms in BBFs, were the main factors explaining Zn biofortification. Bio-based fertilizers also decreased the antagonism between P and Zn and between Fe and Zn. The results demonstrated that the inclusion of BBFs in agrosystems management can contribute to improving the quality of human diets, at least with regard to Zn intake, while also contributing to more sustainable fertilization practices.
Innovation ARIMA models application to predict pressure variations in water supply networks with open-loop control. Case study in Noja (Cantabria, Spain)
(Elsevier, 2025) Muñoz Rodríguez, David; González Ortega, Manuel Jesús; Aguilera Ureña, María Jesús; Ortega Ballesteros, Andrés; Perea Moreno, Alberto Jesús; Ingeniería Aeroespacial y Mecánica de Fluidos
Water utilities are increasingly concerned about losses, leaks, and illegal connections in their distribution networks. Pressure control is typically managed through pressure reducing valves (PRVs) with electrically controlled actuators based on predefined tables according to the pressure at the critical point control (CPC). This open-loop control method lacks direct feedback between the PRV and CPC, making it challenging to distinguish whether pressure variations originate from normal head losses or abnormal network conditions. Unlike traditional applications of ARIMA focused on water demand forecasting, this study explores its novel use in pressure management within distribution networks, aiming to predict P3 (CPC) pressure based on head losses across a defined hydraulic sector. To achieve this objective, a predictive model based on the Box-Jenkins methodology and its variations is implemented to analyse time series data. An action path is established to determine the optimal model—ARIMA, ARMA, ARMAX, etc.—which is subsequently validated using real operational data from Noja, a coastal town in northern Spain characterized by significant seasonal population fluctuations. By accurately forecasting CPC pressure, this system enhances the detection of anomalous patterns, enabling more efficient network pressure management. The study demonstrates the potential of advanced modelling techniques in optimizing water distribution networks, providing valuable insights to improve system efficiency, reliability, and sustainability in urban environments.
On the assessment of channel deepening impacts in micro-meso tidal estuaries: A systematic analysis
(Elsevier, 2025-07) Martín Llanes, Guillermo; López-Ruiz, Alejandro; Ingeniería Aeroespacial y Mecánica de Fluidos; Ministerio de Ciencia e Innovación (MICIN). España; Consejería de Transformación Económica, Industria, Conocimiento y Universidades. Junta de Andalucía
The need for efficient maritime transportation in estuaries has led to the development of diverse dredging strategies to accommodate vessels with deep drafts. Most recent studies assessing the environmental impacts of channel deepening use advanced, tailored models to simulate the long-term response to historical bathymetric changes in estuaries worldwide. However, these models are often time-consuming and highly specific to local conditions, limiting the broader applicability of their results. In addition, a common limitation is the significant time gap between the bathymetric data used, often exceeding 100 years. This makes it challenging to quantify the effects of isolated deepening operations, which is essential for understanding the influence of human intervention on estuarine dynamics. To overcome this limitation while ensuring efficient and adaptable modelling, this paper presents a three-dimensional idealised model (Delft3D) to quantify the short-term, e.g., weeks, hydrodynamic and salinity response to dredging operations in micro-meso tidal, well-mixed estuaries. Implications on channel operativity are also discussed. The numerical experiments examine variations in both channel depth and dredging length. Key findings suggest that dredging length is critical in the estuarine response. Specifically, dredging length has a greater influence on tidal amplification than channel depth. Changes in the flow structure are primarily driven by changes in the barotropic pressure gradient and bed shear forces, which vary spatially along the estuary, defining three distinct regions of behaviour. In addition, salt intrusion increases linearly with channel depth and becomes particularly sensitive to dredging length in shorter operations. Regarding basin management, results reveal that landward operativity is compromised by dredging in the lower river.
Diagnosis by SAM Linked to Machine Vision Systems in Olive Pitting Machines
(MDPI, 2025) Villanueva Gandul, Luis; Madueño Luna, Antonio; Madueño Luna, José Miguel; López Gordillo, Miguel Calixto; González Ortega, Manuel Jesús; Ingeniería Aeroespacial y Mecánica de Fluidos; Ingeniería Gráfica
Computer Vision (CV) has proven to be a powerful tool for automation in agri-food industrial processes, offering high-precision solutions tailored to specific working conditions. Recent advancements in Artificial Neural Networks (ANNs) have revolutionized CV applications, enabling systems to autonomously learn and optimize tasks. However, ANN-based approaches often require complex development and lengthy training periods, making their implementation a challenge. In this study, we explore the use of the Segment Anything Model (SAM), a pre-trained neural network developed by META AI in 2023, as an alternative for industrial segmentation tasks in the table olive (Olea europaea L.) processing industry. SAM’s ability to segment objects regardless of scene composition makes it a promising tool to improve the efficiency of olive pitting machines (DRRs). These machines, widely employed in industrial processing, frequently experience mechanical inefficiencies, including the “boat error,” which arises when olives are improperly oriented, leading to defective pitting and pit splinter contamination. Our approach integrates SAM into n CV workflow to diagnose and quantify boat errors without designing or training an additional task-specific ANN. By analyzing the segmented images, we can determine both the percentage of boat errors and the size distribution of olives during transport. The results validate SAM as a feasible option for industrial segmentation, offering a simpler and more accessible solution compared to traditional ANN-based methods. Moreover, our statistical analysis reveals that improper calibration—manifested as size deviations from the nominal value—does not significantly increase boat error rates. This finding supports the adoption of complementary CV technologies to enhance olive pitting efficiency. Future work could investigate real-time integration and the combination of CV with electromechanical correction systems to fully automate and optimize the pitting process.
Development of a computer vision-based method for sizing and boat error assessment in olive pitting machines
(MDPI, 2025-06-13) Villanueva Gandul, Luis; Madueño Luna, Antonio; Madueño Luna, José Miguel; López Gordillo, Miguel Calixto; González Ortega, Manuel Jesús; Ingeniería Aeroespacial y Mecánica de Fluidos; Ingeniería Gráfica; AGR280: Ingeniería Rural; AGR278: Smart Biosystems Laboratory
Table olive pitting machines (DRRs) are essential in the agri-food industry but face significant limitations that constrain their performance and compromise process reliability. The main defect, known as the “boat error”, results from improper olive orientation during pitting, leading to bone fragmentation, pulp damage, and potential risks to consumer safety. Traditional quality control methods, such as the use of flotation tanks and expert sensory evaluation, rely on destructive sampling, are time-consuming, and reduce overall productivity. To address these challenges, this study presents a novel computer vision (CV) system integrated into a commercial DRR machine. The system captures high-speed images of Gordal olives (Olea europaea regalis) just before pitting; these are later analyzed offline using a custom MATLAB application that applies HSV-based segmentation and morphological analysis to quantify the olive size and orientation. The method accurately identifies boat error cases based on angular thresholds, without interrupting the production flow or damaging the product. The results show that 97% of olives were correctly aligned, with only 1.1% presenting critical misorientation. Additionally, for the first time, the system allowed a detailed evaluation of the olive size distribution at the machine inlet, revealing an unexpected proportion of off-caliber olives. This contamination in sizing suggests a possible link between calibration deviations and the occurrence of boat errors, introducing a new hypothesis for future investigation. While the current implementation is limited to offline analysis, it represents a non-destructive, low-cost, and highly precise diagnostic tool. This work lays the foundation for a deeper understanding of DRR machine behavior and provides a framework for future developments aimed at optimizing their performance through targeted correction strategies.
Recycling Manure as Vermicompost: Assessing Phosphorus Fertilizer Efficiency and Effects on Soil Health Under Different Soil Management
(Springer, 2025) Nieto Cantero, Juan; García López, Ana M.; Recena Garrido, Ramiro; Quintero Ariza, José Manuel; Delgado García, Antonio; Agronomía; Ingeniería Aeroespacial y Mecánica de Fluidos
Vermicompost from organic wastes can provide nutrients and benefits to soil health. Its effects on P availability to plants is still poorly understood, specially under different soil management practices. This work aimed to assess vermicompost as a P fertilizer able to enhance soil functioning. Phosphorus forms of vermicompost were studied by 31P NMR and chemical P fractionation to explain its efficiency as fertilizer. This efficiency was assessed with a pot experiment using soil from two different soil management (conventional tillage–CT – and non-tillage–NT–) and from two depths (0–5 and 20–40 cm). Under NT, the soil showed a higher initial P bioavailability than under CT. In vermicompost, 65% of total P corresponded to ortophosphate, meanwhile 35.4% was extractable with neutral ammonium citrate. Overall, vermicompost increased the physiological P use efficiency by 87% compared to mineral fertilization, this increase being greater under CT (107%) than under NT (70%). Replacement values on a dry matter basis close or even higher than 100% were observed under CT and in subsurface soils under NT, conditions with the lowest P availability to plants. Vermicompost boosted microbial diversity in soils (by 8% according to Shannon index) and alkaline phosphatase and phytase activities, specially under NT. Vermicompost increased Fe and Zn uptake, while decreased the P to Zn molar ratio in spikes. Vermicompost can be a suitable replacement for P mineral fertilizer, in particular in soils with low P availability, providing further benefits such as improved Fe and Zn nutrition and increased microbial diversity and P cycling capacity in soils.
Assessing microbially mediated vivianite as a novel phosphorus and iron fertilizer
(Springer, 2024) Eshun, Lordina Ekua; García López, Ana M.; Recena Garrido, Ramiro; Coker, Victoria; Shaw, Samuel; Lloyd, Jonathan; Delgado García, Antonio; Agronomía; Ingeniería Aeroespacial y Mecánica de Fluidos
Background Microorganisms can transform phosphorus (P)-enriched iron (Fe)-oxide sludge into products with higher P concentration or can directly promote the precipitation of P-rich compounds from water. However, there is no evidence of these products’ efciency as fertilizers. This study aimed to assess the efectiveness of microbi ally mediated vivianite (biovivianite) as P and Fe fertilizer for durum wheat and white lupin, respectively. Results To this end, two completely randomized block experiments were conducted with wheat (phosphorus (P) experiment) and white lupin (iron (Fe) experiment). The P and Fe sources used included biovivianite produced by microbial reduction of P-containing ferrihydrite at pH 6.5 (VivInsol6.5) and pH 7.0 (VivInsol7.0), biovivianite pro duced with soluble Fe(III) citrate (C6H5FeO7) in the presence of soluble phosphate at pH 7 (VivSol), and vivianite from a commercial company (ComViv). Potassium dihydrogen phosphate (KH2PO4) was used as a reference fertilizer in the P experiment, and Fe-EDDHA and Fe(II)-sulfate (FeSO4.7H2O) were used in the Fe experiment. Total P uptake by wheat plants from the product dominated by vivianite and phosphate-green rust (VivSol) was not signifcantly diferent from KH2PO4. The relative P use efciency, i.e., the equivalence in terms of P recovery of VivSol was 74% of KH2PO4, making VivSol the efective P source for durum wheat among the products tested (aside from KH2PO4). For Fe uptake, product dominated by vivianite and metavivianite (VivInsol7.0), was the most efective Fe source for white lupin followed by Fe-EDDHA, ComViv, and VivSol with VivInsol6.5 as the least efective but without signif cant diferences with Fe(II)-sulfate. The average crystallite sizes of the biovivianite were 59 nm, 63 nm, and 66 nm for VivSol, VivInsol7.0, and VivInsol6.5, respectively. Conclusions The mineral constituents of the biovivianite coupled with their nano-crystallite sizes explained its efectiveness as P and Fe fertilizers. The results reveal that biovivianite production is a novel way of producing efcient P and Fe fertilizers from P-enriched Fe sludge or P-rich water. Thus, it can be used for producing fertilizers with high P and Fe concentrations from water purifcation, providing new tools for a circular economy approach in the use of a non-renewable resource such as P.
Modeling Probabilistic Safety Margins in Convective Weather Avoidance Within European Airspace
(MDPI, 2025) Núñez Portillo, Juan Manuel; Franco Espín, Antonio; Valenzuela Romero, Alfonso; Ingeniería Aeroespacial y Mecánica de Fluidos; Ministerio de Ciencia e Innovación (MICIN). España; TEP945: Ingeniería Aeroespacial
This paper presents an ensemble of observed safety margins for aircraft deviations due to convective weather in European airspace. Leveraging historical high-resolution traffic and weather radar data from the FABEC and UK-Ireland FAB regions, meaningful lateral margins are determined based on composite reflectivity and echo top data. These margins enable the estimation of probability distribution for safety distances, supporting both deviation discrimination and lateral separation assessment. Cross-validated results compared against standard binary classifiers and deterministic baseline models indicate that the model effectively distinguishes deviations from non-deviations and accurately estimates lateral margins. This framework enhances understanding of pilot decision-making, contributing to more informed air traffic management and aviation safety strategies.
Two-dimensional global stability analysis of elongated bubbles moving in a horizontal tube
(American Physical Society, 2025) Magnini, Mirco; Herrada Gutiérrez, Miguel Ángel; Ingeniería Aeroespacial y Mecánica de Fluidos; Engineering and Physical Sciences Research Council (UK); Ministerio de Economia, Industria y Competitividad (MINECO). España; University of Warwick
The linear stability of an elongated axisymmetric gas bubble transported by a liquid in a capillary tube is analyzed through the use of numerical simulations. The study focuses on the influence of inertia, characterized by the Reynolds number (Re) and the imposed flow rate, characterized by a capillary number (Cal), on the stability of the bubble tail, which exhibits ripples at high Re. The numerical approach utilizes a boundary-fitted method in a reference frame anchored to the bubble, combined with a mixed spatial discretization based on spectral collocation in the radial direction and finite differences in the axial direction. This framework enables the computation of steady nonlinear solutions through a Newton iteration scheme and facilitates the linear stability analysis of these solutions. Direct numerical simulations using the volume of fluid method in OpenFOAM are also performed to corroborate the results of the stability analysis. We perform systematic simulations for Cal = 0.005 − 0.04 and observe that the system becomes unstable, with the emergence of oscillations at the rear of the bubble, when the Reynolds number grows above a critical value, designated as Re∗; this critical value is dependent on the capillary number. The instability is due to the increased inertia of the recirculating flow in the liquid behind the bubble, which impinges its rear meniscus. A modified Weber number Wep, based on the relative velocity between the external flow and the bubble, is introduced to describe the competition between the destabilizing pressure force acting on the bubble rear and surface tension. Our results show that the bubble dynamics become unstable for a critical value, We∗ p ≈ 3.65, which remains quite uniform across the range of capillary numbers tested, and divides the Cal − Re diagram into stable and unstable regimes. Our findings offer insights into the behavior of bubbles in microfluidic applications, with implications for heat transfer, mass transfer, and cleaning processes in microchannels.
A note on the thrust of airfoils
(Cambridge University Press, 2025-06-10) Gordillo Arias de Saavedra, José Manuel; Ingeniería Aeroespacial y Mecánica de Fluidos; TEP103: Mecánica de Fluidos
Here, we show that the thrust force of oscillating airfoils calculated within the linearised potential ﬂow approach by means of the vortex impulse theory coincides with the one resulting from the integration of the unsteady pressure distribution around the solid obtained by Garrick (1936) when the vertical component of the wake velocity is calculated self-consistently and the analysis retains the contribution of the ﬂux of horizontal momentum induced by the starting vortex. The limitations of the self-consistent linearised potential ﬂow approach for predicting the thrust force of airfoils oscillating periodically with small amplitudes but large values of the reduced frequency are also discussed, as well as the reasons behind the ability of other results in the literature to approximate measurements better than Garrick’s theory. In fact, for those cases in which the airfoil oscillates periodically, the ﬂux of horizontal momentum induced by the starting vortex is negligible and the vortices in the wake are convected parallel to the free-stream velocity, we have deduced an equation for the mean thrust coefﬁcient which differs from previously published results and is in agreement with experimental and numerical results. In addition, for those cases in which the airfoil is suddenly set into motion, we have also deduced an equation that retains the effect of the starting vortex and correctly quantiﬁes the transient thrust force.
Transient bubble rising in the presence of a surfactant at very low concentrations
(Elsevier, 2025) Fernández Martínez, Daniel; Cabezas, M. G.; López-Herrera Sánchez, José María; Herrada Gutiérrez, Miguel Ángel; Ingeniería Aeroespacial y Mecánica de Fluidos; Ministerio de Ciencia e Innovación (MICIN). España; Agencia Estatal de Investigación. España
We study the formation of the dynamic adsorption layer when a bubble is released in a tank containing water with a tiny amount of surfactant. The influence of the sorption kinetic constants is examined by comparing the experiments with Sodium Dodecyl Sulfate (SDS) and Triton X-100. The experiments allowed us to determine the parameter conditions that lead to a stable bubble rising and to validate the simulation. A simple scaling analysis and the simulation show that the formation of the dynamic adsorption layer can be split into three phases characterized by disparate time scales. The mechanisms controlling those phases are surfactant convection, adsorption–desorption, and diffusion. The amount of surfactant adsorbed onto the interface increases monotonously throughout the three phases. The experiments and the simulation show that the rising velocity reaches a maximum at times of the order of Kd-1( Kd is the desorption constant) when the dynamic adsorption layer is practically formed. This occurs even when only traces of surfactant are present in the liquid. The non-monotonous behavior of the maximum surfactant surface concentration is explained in terms of the reverse flow in the rear of the bubble right after the bubble release. This work contributes to the understanding of the complex interplay between hydrodynamics and surfactant transport and kinetics over bubble rising.

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