Search Results (2,574)

The Droplets Triboelectric Nanogenerator (DTENG) possess distinctive merits in harvesting ambient hydropower into usable electricity. Nevertheless, droplet spreading, contact separation behavior, and dynamic interfacial interactions on insulating film surfaces are extremely sensitive to external environmental factors, giving rise to complicated nonlinear output characteristics. Herein, this work reports a droplet-driven TENG based on fluorinated ethylene propylene (FEP) thin films. We systematically explore how electrode geometry, droplet falling height, substrate inclination angle, and droplet flow rate modulate electrical output performance, and further clarify the fluid-triboelectric electron transfer between droplet hydrodynamic evolution and electric signal generation. Notably, we identify the retraction current during droplet recession, a signal largely neglected in previous solid–liquid TENG research, which complements the fundamental mechanism of interfacial charge transfer. This work not only provides a systematic experimental basis for understanding the working mechanism of DTENG, but also lays a theoretical and practical foundation for developing efficient and controllable water energy collection and self-powered sensor systems. Full article

The determination of optimal geometric characteristics of a catamaran that minimize vessel motion responses under prescribed design and operational conditions remains insufficiently addressed in existing engineering practice. This study presents a systematic methodology for the evaluation of catamaran seakeeping performance through the structured parametric comparison of principal geometric parameters. The proposed methodology comprises the identification of relevant geometric variables, the specification of their admissible variation ranges in accordance with design constraints, the selection of appropriate numerical evaluation tools, and the quantitative analysis of resulting motion responses. The objective is to determine parameter combinations that yield minimum motion amplitudes. The methodology presented in this article is partly a complex methodology for evaluation of seakeeping and total resistance, and partly selection of the most favorable combinations of geometrical parameters satisfying the design task parameters across both above-mentioned hydrodynamic qualities. The resistance part of the methodology is presented in previous works with links and description provided in this article. A graphical system for presenting simulation results is developed, allowing arrangement of the calculation results on one horizontal axis, representing catamaran length variations, grouped by the speed and demihull separation values and including catamaran demihull symmetry considerations. Aligned under each other, the graphs provide an intuitive interpretation of total resistance trends and seakeeping across various geometric configurations and operational speeds. This method, the seakeeping part of which is illustrated in the results paragraph, enables a comprehensive comparison of multiple design variants within a clear visual framework. The methodology is applied to a representative catamaran configuration by parametrically varying key geometric characteristics, including vessel length, demihull separation, and hull symmetry. The corresponding seakeeping responses are evaluated using the Maxsurf Motions computational framework. The results demonstrate that systematic variation and analysis of geometric parameters enable the identification of configurations with significantly reduced motion amplitudes. Pitching RAO amplitudes for different catamaran lengths can vary 45–50%, for demihull separation—25–50% and for asymmetry 27–50%. Heaving RAO amplitudes for different catamaran lengths can vary 45–50%, for demihull separation—32–65% and for asymmetry 30–60%. The findings indicate that demihull separation, hull-form symmetry, and overall vessel length each play a significant role in determining catamaran seakeeping performance. The proposed approach provides a robust basis for the early-stage design structured parametric comparison of catamarans, facilitating the selection of geometric configurations that minimize projected vessel motions and improve overall seakeeping performance. Full article

Irregular migration across the Mediterranean Sea causes thousands of deaths annually, mostly due to shipwrecks involving structurally inadequate vessels navigating under severe meteo-marine conditions. The forensic investigation of human remains recovered in such contexts is particularly challenging due to advanced decomposition and the absence of documentary evidence linking victims to a specific departure event. In the present study, a methodology is developed and validated for reconstructing the most probable departure location of human remains recovered at sea, through the integration of backward Lagrangian drift simulations with large-scale oceanographic and atmospheric datasets provided by the Copernicus Marine Service (CMEMS). The methodology was applied to five bodies recovered in the Aeolian Islands area (Sicily, Italy) between March and June 2024. Simulations were performed using the OpenDrift Leeway model, with an ensemble of several drifters released across five temporal offsets per recovery site. Results were synthesised through a drift probability metric $P_d$ and a newly proposed Hydrodynamic Connectivity Index (HCI), cross-referenced with documented shipwreck incidents and complemented by a wave climate analysis. The methodology successfully identified the port of Bizerte (Tunisia) and the shipwreck event of 5–6 February 2024 as the most probable origin, in full agreement with independent forensic findings, demonstrating the reliability of the proposed approach for forensic reconstruction of shipwreck events in the central Mediterranean and the possibility of being used as aid in recovering further remains. Full article

This study investigated the effect of brief mechanical homogenization using a household blender on the properties of nopal mucilage and its performance in removing potentially toxic elements (PTEs), specifically Pb, Ni, As, Cd, and Zn, from a real cyanidation barren solution. An aqueous extract from Opuntia ficus-indica cladodes was homogenized for 0, 30, or 60 s before spray drying, yielding powders designated as CA, CB, and CC. The powders and water-reconstituted dispersions were characterized and evaluated in coagulation–flocculation assays. Homogenization reduced water activity and average hydrodynamic diameter and significantly modified the ζ potential, although the effects were not proportional to processing time. At 10% w·v⁻¹, the reconstituted mucilages showed frequency-dependent viscoelastic behavior consistent with a transient gel-like organization. All treatments removed more than 98% of Pb, Ni, and As at doses of 200–800 mg·L⁻¹. Cd removal was more variable and significantly affected by mucilage type, whereas Zn showed lower, non-monotonic removal. ESEM–EDS detected PTE-bearing inorganic domains within the recovered flocs, corroborating transfer from the liquid to the solid phase. Overall, mechanical homogenization modified the colloidal, supramolecular, and gel-related properties of spray-dried nopal mucilage, which showed potential as a multifunctional hydrocolloid for treating chemically complex cyanidation process streams. Full article

To mitigate the negative impacts of traditional rigid revetments on river ecosystems, this study focuses on perforated plate grid revetments, aiming to reveal the hydrodynamic mechanisms and parameter collaborative optimization pathways that simultaneously achieve anti-scour stability and ecological water exchange. A series of flume scour tests were conducted, combined with high-resolution large eddy simulation (LES) validated by experimental data, to systematically analyze the regulatory effects of key design parameters—such as opening ratio and longitudinal offset angle—on near-bottom flow velocity attenuation, vortex structures, and water exchange efficiency. The results indicate that a prototype parameter combination of 0.25 m grid height and 0.50 m plate grid spacing can reduce local scour depth by about 30% and enhance vertical exchange through the synergy of jetting from the openings and internal vortices. The longitudinal offset of adjacent holes may enhance the transverse water exchange but may also significantly reduce the longitudinal exchange intensity; hence, further research is needed. A hole-to-baffle height ratio greater than 0.40 is identified as a critical threshold for improving exchange efficiency. This study proposes a collaborative design framework in which grid spacing controls scour safety and aperture parameters regulate exchange functions, providing an experimental basis for the precise design and performance enhancement of ecological revetments. Full article

Lipid-based nanoparticles are widely explored as non-viral vectors for nucleic acid delivery, where the molecular structure of cationic lipids strongly determines their performance. Five-membered heterocyclic linkers were explored as a new structural motif in cationic amphiphilic lipids for the development of promising gene delivery candidates. Novel lipids incorporating pyrrole, furan, and thiophene linkers were synthesized alongside structurally related aliphatic analogues, enabling systematic evaluation of how linker type influences physicochemical behavior and self-assembly properties. Self-assembly behavior in aqueous media was characterized by dynamic light scattering, and pDNA encapsulation efficiency was measured using the Quant-iT Pico-Green method. The resulting liposomes exhibited hydrodynamic diameters ranging from 92 to 1317 nm, while corresponding lipoplexes ranged from 302 to 1159 nm. Amphiphiles containing heterocyclic linkers demonstrated high pDNA encapsulation (>80% at optimal N/P ratios), whereas aliphatic analogues showed significantly reduced performance. These results demonstrate that linker structure strongly influences both self-assembly and nucleic acid binding properties. By evaluating structure–activity relationships, five-membered heterocycles are proposed as promising structural elements for the rational development of lipid-based gene delivery candidates. Full article

Since 2011, massive strandings of pelagic Sargassum have become a recurrent environmental hazard across the tropical Atlantic and Caribbean archipelago, creating an urgent need for reliable short-term drift forecasts to support coastal risk management. This study evaluates key sources of uncertainty in operational Sargassum drift forecasting by analyzing the sensitivity of Lagrangian simulations to the representation of floating material and to environmental forcing fields. The analysis uses two complementary observational datasets: trajectories of four GPS-tracked Sargassum mats deployed near Puerto Rico and thirteen 24 h displacement vectors derived from sequential Sentinel-3 satellite detections across the tropical North Atlantic. Drift simulations were performed with the MOTHY model under multiple configurations, testing two material parameterizations, different atmospheric forcings, and several ocean circulation products and vertical current integration strategies. The results indicate that the best agreement with observed trajectories is obtained for partially immersed structures, highlighting the importance of balancing wind exposure and hydrodynamic drag. Sensitivity experiments further show that ocean circulation forcing dominates trajectory skill, while higher-resolution atmospheric forcing provides limited improvement under offshore conditions. Overall, the study confirms the importance of accurately representing upper-ocean transport processes and provides observational support for several operational choices implemented in the Météo-France Sargassum forecasting system. Full article

Impact dynamics problems are ubiquitous in various engineering applications, often involving nonlinear phenomena such as material fracture, damage, and fragmentation. It poses significant challenges to numerical simulation methods. To deal with these challenges, this paper develops an adaptive axisymmetric coupling method that combines the edge-based smoothed finite element method (ES-FEM) with smoothed particle hydrodynamics (SPH), referred to as the ES-FEM-SPH method. Initially, the entire computation employs ES-FEM, which effectively alleviates the excessive stiffness inherent in conventional FEM while maintaining high accuracy, particularly when using linear triangular elements. During the simulation, if any element undergoes severe distortion, the algorithm converts it into an SPH particle and continues the computation with SPH automatically. Thus, it can effectively address issues such as large deformation. To validate the efficacy and reliability of the proposed method, this study performs numerical simulations on several representative cases, including Taylor bar impact, projectile penetration into aluminum plates, and flat-nosed projectile impact on metal target plates. The results demonstrate that the adaptive axisymmetric ES-FEM-SPH coupling method exhibits good performance in both computational accuracy and efficiency, making it well suited for numerical simulations of impact-related problems and holding substantial promise for engineering applications. Full article

Computational Fluid Dynamics (CFD) was applied to an intermittent anoxic/aerobic Moving Bed Biofilm Reactor (MBBR) operated under six different aeration intermittency cycles and dissolved oxygen concentration levels. Experimental results showed that most aeration cycles did not provide a sufficiently long anoxic phase to sustain effective denitrification, thereby limiting NOx removal efficiency. This behavior was not adequately captured by simulations performed using conventional biological models (BioWin), which rely on the assumption of complete mixing. In contrast, the CFD model implemented in ANSYS Fluent 2024 R2 enabled a detailed characterization of reactor hydrodynamics and the identification of several inefficiencies, including short-circuiting, back-mixing, and the presence of dead zones. Notably, the simulations revealed a pronounced asymmetric distribution of carriers within the reactor, with the majority accumulating along one side, leaving a significant fraction of the reactor volume largely unoccupied. Further analysis indicated that this phenomenon was caused by a design flaw—specifically, the asymmetric placement of the aerators—combined with an excessively high air injection flow rate. Full article

To improve the amphibious locomotion capability of robots in aquatic and terrestrial environments, this paper proposes a novel frog-inspired hybrid-driven amphibious robot inspired by the amphibious locomotion characteristics of frogs. Unlike existing frog-inspired robots limited to single-mode jumping or swimming, this robot adopts an innovative hybrid actuation mechanism to simultaneously achieve frog-like swimming and jumping capabilities. On land, it uses a combustion-driven hindlimb propulsion mechanism paired with a linkage-based forelimb posture adjustment mechanism to realize frog-like jumping; in water, it employs a cable-driven linked hindlimb mechanism combined with a controllable soft extension-driven webbed foot to accomplish frog-like swimming. Furthermore, the instantaneous combustion thrust during frog-like jumping and the hydrodynamic thrust during swimming are calculated. The mapping relationships between the take-off attitude angle, hydrogen–oxygen mixture charge, and jumping performance, as well as the motion pattern between hindlimb motion parameters and swimming thrust, are derived. Finally, experimental results demonstrate that the robot achieves a swimming speed of 79 mm/s, a jumping height of 560 mm, and a jumping distance of 1200 mm, while being capable of performing continuous amphibious locomotion. Full article

The growing demand for high-speed marine transportation requires continuous improvement in ship design to achieve higher hydrodynamic efficiency. From an engineering design perspective, hull form modification is a key approach to optimizing the performance of planing vessels, particularly through the implementation of stepped hull configurations. This study aims to investigate the effects of step geometry and step position on the resistance and trim characteristics of a planing hull based on Taunton et al.’s Model C, with the objective of improving vessel efficiency. The design methodology integrates hull geometry modification, parametric variation in step position and step height, and numerical performance assessment. In this research, the governing equations are solved using the Reynolds-Averaged Navier–Stokes (RANS) framework with the Finite Volume Method (FVM) as the discretization technique. The turbulence model used is k-ω SST, while the interaction between water and air phases is represented using the Volume of Fluid (VOF) method. From a design performance perspective, the results demonstrate that stepped hull geometry significantly influences resistance and trim characteristics. The optimal design configurations achieved a resistance reduction of up to 17.93% and a trim of 1.53° was achieved with a stepped position of 430 mm from the transom and a stepped height of 25 mm (Model A3) at Fr 2.28. Meanwhile, a resistance reduction of 15.49% and a trim of 1.46° were observed for a stepped position of 860 mm from the transom and a stepped height of 25 mm (Model B3) at Fr 2.72. These findings highlight the importance of step geometry and placement as key design variables in improving planing hull performance. This study demonstrates that CFD-based evaluation can effectively support engineering design decisions for stepped hull optimization, providing a systematic approach for improving hydrodynamic efficiency in high-speed vessel design. Full article

Magnesium-based alloys remain poorly researched, particularly regarding their behavior and resistance under hydrodynamic loading conditions. Interest in these materials is driven by their low density, lower even than that of aluminum alloys, and their excellent pressure die-casting capability, leading to manufacturing components with high geometric accuracy and structural homogeneity. Due to their biodegradability and biocompatibility, recent research has focused on using them in reconstructive surgery devices, similar to Zn-Mg alloys. As the blood circulatory system can, at certain stages, be considered similar to a hydraulic system, it is subjected to hydrodynamic flow regimes, including cavitation erosion. In this context, the current research, conducted on the AM50 magnesium-based alloy, provides new insights into its behavior and structural resistance exposed to shock waves and microjets generated by cavitation. Cavitation tests were performed using a standard 20 kHz vibratory device on three material conditions: one semi-finished (initial) state and two aged, heat-treated states at 200 °C for 12 and 24 h. Analyses of the characteristic erosion curves, cavitation resistance parameters, and macro- and microstructural examinations of the eroded surfaces revealed that, compared with the semi-finished condition, the applied heat-treatment regimes increased the HV₅ hardness by 6.8–17% and the cavitation resistance by 27–61%. Full article

Nanobubbles have attracted increasing interest in food systems because they can modify gas dispersion, interfacial transport, washing performance, preservation processes, and the structures of dispersed matrices. However, their behavior cannot be interpreted based on bubble size alone. Proteins, polysaccharides, lipids, salts, colloidal particles, gas composition, and processing conditions can alter interfacial adsorption, gas transfer, bubble persistence, and matrix organization in food systems. This review examines the physicochemical mechanisms proposed to explain nanobubble persistence and functionality, with an emphasis on surface charge, interfacial adsorption, gas supersaturation, confinement, and interactions with food biopolymers. A central distinction is made between passive nanobubble-containing systems and externally activated systems involving hydrodynamic cavitation, ultrasound, plasma, pressure fluctuations, and reactive gases. Under passive conditions, nanobubbles mainly act as gas–liquid interfaces that influence local transport and adsorption. In activated systems, microbial inactivation, reactive oxygen species formation, and apparent mass-transfer enhancement often arise from external energy input, gas chemistry, turbulence, and transient supersaturation rather than from nanobubbles alone. Interfacial stability is used here as an organizing concept to connect nanobubble persistence, food-matrix interactions, generation methods, characterization limitations, and interpretation of reported technological effects. Current methods, such as dynamic light scattering and nanoparticle tracking analysis, provide useful size and concentration estimates but cannot unambiguously distinguish nanobubbles from protein aggregates, fat droplets, micelles, polysaccharide assemblies, and other colloidal structures in complex matrices. Therefore, reliable interpretation requires complementary methods, appropriate controls, and standardized reporting of gas composition, generation method, energy input, matrix properties, and processing conditions. Thus, nanobubble-containing technologies show promise for food processing; however, their value depends on the separation of nanoscale interfacial effects from concurrent hydrodynamic, chemical, and matrix-dependent phenomena. Full article

Accurate prediction of contaminant transport and self-purification processes in rivers remains challenging because pollutant dispersion, biochemical reactions, and hydrodynamic conditions interact across multiple spatial scales. This study aims to develop and compare mathematical models for soluble contaminant transport and biodegradable organic matter removal in channels and rivers. Unsteady advection–diffusion–reaction equations were formulated for one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) transport scenarios and solved through numerical techniques based on the transformation of partial differential equations into systems of ordinary differential or algebraic equations. In parallel, the classical Streeter–Phelps model and an extended formulation incorporating turbulent diffusion were implemented to evaluate organic load degradation and oxygen deficit dynamics. Simulations were performed using a Matlab R2019a-based computational framework under representative hydraulic and reaction conditions obtained from literature data and empirical correlations. The results showed that, under specific conditions, the 3D model reproduced trends comparable to those predicted by the 2D model, while the latter approached the behavior of the 1D formulation. The Streeter–Phelps model predicted an organic load removal efficiency of 97.74%, a purification index of 1.9564, a critical time of 18.43 h, and a critical distance of 6.93 km. These findings provide a useful framework for river water-quality assessment and support future applications involving complex hydrodynamic and pollutant-loading scenarios. Full article

This study consists of two main components. The first part establishes a seakeeping assessment method, while the second part focuses on hull-form optimization with seakeeping performance as the objective. For the seakeeping analysis, the Lewis conformal mapping method is used to calculate the sectional hydrodynamic coefficients. Strip theory is then applied to obtain the global hydrodynamic coefficients of the hull. The coupled heave and pitch motion responses are calculated and compared with nonlinear time-domain simulation results and experimental data, showing good agreement. A multivariate linear regression model is established to approximate the relationship between the principal hull-form parameters and the heave and pitch RAOs. The comparison between the regression model and strip theory results shows that the prediction error remains within 5%, indicating that the regression model can provide an efficient surrogate objective function for hull-form optimization. The particle swarm optimization (PSO) algorithm is then employed to optimize the hull form, with the ship length, breadth, draft, and block coefficient considered as design variables. To further evaluate the optimized hull, additional calculations are conducted under different Froude numbers and encounter angles. Under head sea conditions with varying Froude numbers, the optimized hull reduces the peak heave RAO by 11.6–31.1% and the peak pitch RAO by 8.6–17.9%. Under different encounter angles at F_r = 0.3, the reductions in peak heave and pitch RAOs are 31.1–33.9% and 16.5–18.8%, respectively. These results demonstrate that the proposed regression assisted PSO optimization framework can effectively reduce the heave and pitch responses of the Wigley hull under the investigated regular wave conditions. Full article