Search Results (7,931)

The design of tubular flocculators has advanced in the pursuit of more efficient and compact water treatment systems. Helically coiled tube flocculators (HCTFs) are known for generating stable secondary flows and uniform hydrodynamic patterns after the development length. However, their constant geometry restricts the hydrodynamic variability required for optimized flocculation. This study introduces the spirally coiled tube flocculator (SCTF), characterized by a winding diameter that varies along its length. CFD simulations and laboratory-scale experiments compared HCTFs and SCTFs in terms of turbidity removal capacity, axial velocity profiles, secondary flows, streamlines, and global velocity gradients. The SCTF outperformed the HCTFs under all evaluated configurations, achieving up to 98.2% turbidity removal. The results emphasize the potential of spiral geometries to enhance process efficiency and highlight the need to reconsider hydrodynamic strategies in the design of tubular flocculators. Full article

The parameter optimization design of a power-cycling hydrodynamic mechanical transmission (PCHMT) is an important approach to improving the fuel economy of wheel loaders. First, the output capacity characteristics of the PCHMT were analyzed, revealing the qualitative relationships among structural parameters, efficiency, and the output capacity coefficient. Second, 400 sets of V-cycle operation condition tests were conducted on loaders using five different materials, and a representative loading–hauling cycle was synthesized with the K-means clustering algorithm. Third, a parameter optimization model for the PCHMT was developed based on its output capacity characteristics, and the optimal structural parameters were determined using a genetic algorithm. Finally, a simulation model of the loader powertrain was established to compare fuel consumption under optimal and non-optimal parameters. The results show that although transmission efficiency at the same speed ratio is higher with non-optimal parameters, fuel consumption with optimal parameters is 2.6% lower, confirming the effectiveness of this optimization design method. Full article

Urban coastal areas are increasingly vulnerable to compound flooding due to the convergence of extreme rainfall, storm surges, and infrastructure aging, especially in high-density settings. This study proposes and empirically validates a multi-scale strategy for enhancing urban flood resilience in the Macau Peninsula, a densely built coastal city with complex flood exposure patterns. Building on a previously developed network-based resilience assessment framework, the study integrates hydrodynamic simulation and complex network analysis to evaluate the effectiveness of targeted interventions, including segmented storm surge defense barriers, drainage infrastructure upgrades, and spatially optimized low-impact development (LID) measures. The Macau Peninsula was partitioned into multiple shoreline defense zones, each guided by context-specific design principles and functional zoning. Based on our previously developed flood simulation framework covering extreme rainfall, storm surge, and compound events in high-density coastal zones, this study validates resilience strategies that achieve significant reductions in inundation extent, water depth, and recession time. Additionally, the network-based resilience index showed marked improvement in system connectivity and recovery efficiency, particularly under compound hazard conditions. The findings highlight the value of integrating spatial planning, ecological infrastructure, and systemic modeling to inform adaptive flood resilience strategies in compact coastal cities. The framework developed offers transferable insights for other urban regions confronting escalating hydrometeorological risks under climate change. Full article

The wire drawing process, used for both ferrous and non-ferrous metals, employs different machines depending on the material and wire diameter: breakdown, single- or multi-wire machines for non-ferrous, and bull block machines for ferrous and non-ferrous alloy wires. In all cases, wire is drawn through dies by tensile forces, with die design, material, and lubrication crucial for reducing friction, dissipating heat, and ensuring quality. Die type and geometry, lubricant, drawing speed, and machine configuration are the main process variables. The present work evaluates the effects of die type, lubricant, and drawing speed on Zn–Al alloy wire drawing (Ø2.18 to Ø2.00 mm) using a Taguchi L9 (3³) design of experiments. Three lubricants (Multidraw oil/water, Multipress oil and water/oil emulsion), three dies (conventional, carbide 19.38-grade pressure die, carbide H3F-grade pressure die), and three drawing speeds (0.16 to 0.28 m/s) were tested. Results have shown that lubricant and die geometry dominate process performance. Pressure dies reduced drawing force by up to 8% versus the conventional die, and emulsion increased force by 14% compared to oils. Output wire temperatures increased with speed, peaking at 46.5 °C with water emulsion oil and pressure die with H3F carbide, while Multidraw oil kept values ~20% lower. However, emulsions lowered the die output temperatures by 15–25% compared to oils. The coefficient of friction averaged μ = 0.104, with pressure dies yielding the lowest values (0.091–0.096, ~20% below conventional). Surface quality was governed mainly by lubricant effectiveness, with pressure-drawing dies ensuring dimensional accuracy and surface cleanliness. The study identifies lubricant selection as the most influential factor, followed by die type, providing a basis for optimizing efficiency and product quality in the wire drawing of ZnAl15% alloy. Full article

This study investigates the hydrodynamic response of a spar-type buoy equipped with a solid, perforated, and novel corrugated plate appendage introduced here for the first time to enhance motion damping. A hybrid approach combining time-domain CFD simulations and frequency-domain potential-flow analysis was employed, providing a framework to incorporate viscous effects that are often omitted in potential-flow models. In the first stage, free-decay simulations were carried out in ANSYS Fluent for a baseline spar and three appendage-equipped configurations. The resulting heave and pitch decay responses were analyzed to determine natural frequencies and viscous damping coefficients. Prior to that, the CFD solver was validated and verified against published experimental data, confirming the reliability of the numerical setup. In the second stage, frequency-domain hydrodynamic diffraction analysis was conducted in ANSYS AQWA, and the CFD-derived viscous damping coefficients were incorporated into the potential-flow model to improve motion predictions near resonance. The comparison between RAOs with and without viscous damping indicated reductions of approximately 55–62% in heave and 41–60% in pitch at resonance, with the perforated plate consistently yielding the highest damping and lowest RAO peaks. This work introduces the first corrugated plate appendage design for spar buoys and establishes a validated CFD–potential-flow hybrid framework that enables more realistic motion predictions and provides practical design guidance for damping-enhanced spar buoys in offshore energy applications. Full article

A 2D numerical model for viscous flow is established in OpenFOAM version 10 to analyze the hydrodynamic response of submarine power cables for offshore wind turbines under combined wave–current conditions. It focuses on analyzing the effect of the cable suspension ratio e/D and the current-to-wave velocity ratio U_c/U_m on the Morison coefficient of the suspended cable. The results indicate that for the cable suspension ratio e/D of less than 0.5, the strength of the dependence of both the drag coefficient C_d and inertia coefficient C_M on the cable suspension ratio e/D is significantly influenced by the current-wave-ratio U_c/U_m, while this dependence becomes less pronounced for e/D greater than 0.5. And the inertia force coefficient C_M decreases monotonically with the current-to-wave velocity ratio U_c/U_m, while the drag force coefficient C_d demonstrates a more complex, non-monotonic relationship with it. Based on the simulation results in this paper, a quantitative relationship between C_d, C_M, and the key governing parameters is established using a two-layer feedforward neural network model, providing a method for predicting wave–current forces on subsea suspended cables. Full article

This paper systematically investigates the interaction between pipes and soil under geo-logical disaster conditions by combining small-scale physical experiments with mul-ti-method numerical simulations. Three analytical models—namely the Smoothed Particle Hydrodynamics-Finite Element Method (SPH-FEM) model, the traditional FEM model, and the soil spring-based Pipe–Soil Interaction (PSI) model—are employed to comparatively analyze their applicability across different geohazard scenarios. The study found that the PSI model overpredicted pipeline strain responses, indicating that traditional soil spring analytical models require modification. The traditional FEM model provided the most accurate predictions under small-displacement conditions, while the SPH-FEM model yielded more reliable results for large-displacement scenarios. The novelty of this study lies in its systematic exploration of the applicability of these three methodologies, providing scientifically grounded simulation tools for numerical modeling in engineering practice. Full article

Previous studies on improving journal bearing performance have predominantly overlooked the combined effects of the surface textures, circumferential oil grooves, eccentricity ratio, and misalignment. To address this gap, this study employed an adjoint -based optimization framework to optimize the LCC (load-carrying capacity) of journal bearings based on the mixed lubrication model. By incorporating the influence of the circumferential oil groove, the influences of the oil supply pressure, eccentricity ratio, and misalignment angle on the bearing performance and optimal texture evolution were studied. The results show that increased inlet oil pressure shortens textures and reduces the LCC enhancement, while misalignment boosts the absolute LCC but diminishes the relative benefit of textures. Bidirectionally optimized textures maintain robust performance under reverse rotation, with LCC improvements of 12.00 N at an eccentricity ratio (ER) of 0.8. In contrast, unidirectional textures may impair performance, with a reduction of up to –19.53 N. It is recommended to employ symmetric textures for bidirectional operation and to limit misalignment in order to retain the benefits of surface texturing. This research provides a practical foundation for designing high-performance journal bearings. Full article

The parameter optimization of marine hydrodynamic models currently relies predominantly on expert empirical knowledge, but the quantitative indicators and weighting mechanisms for rapid calibration remain unclear due to inherent model uncertainties and complexities. This study addresses these challenges through expert questionnaires that collect fuzzy evaluations of calibration criteria, developing an integrated methodology combining the theory of axiomatic fuzzy set (AFS) with principal component analysis (PCA). Numerical case studies quantify calibration indicator weights and assess critical parameter impacts, revealing that bathymetry and roughness coefficients predominantly govern simulation accuracy. Elevated roughness conditions demonstrate two regimes: (1) at 1–2 × baseline roughness, strong positive correlations (with a coefficient of determination R² increased by up to 0.568 compared to baseline) confirm effective model-data matching for tidal levels/currents; (2) beyond 2 × baseline roughness, progressive correlation decay accompanies increasing coefficients, indicating amplified simulation–measurement discrepancies. Notably, under reduced roughness conditions, high accuracy persists during spring/mid-tide phases but significantly diminishes during neap tides, demonstrating enhanced roughness sensitivity in low-tidal energy regimes. Full article

In recent decades, increasing anthropogenic pressure and climate change have made the protection and sustainable management of groundwater resources essential. In this context, the identification of aquifer recharge zones, especially those characterized by rapid groundwater flow and high vulnerability to surface pollution sources, becomes a priority for the protection of underground resources. In the Po Plain (northern Italy), based on the lithological, geometric, hydraulic, and hydrodynamic characteristics of the aquifers, the recharge areas are mainly located in the alluvial fans of the Alpine and Apennine foothills. Due to the high hydraulic conductivity of the aquifer, the shallow depth of the water table and the agricultural activities, groundwater resources are vulnerable to nitrate (NO₃⁻) contamination. Given this background, the present study introduces a novel methodological approach based on the geochemical signature of groundwater, indicated by the presence of bicarbonate (HCO₃⁻) and NO₃⁻ ions, aimed at identifying aquifer recharge areas. Specifically, by analyzing time series of NO₃⁻ and HCO₃⁻ concentrations for the period 2012–2023, and applying criteria of an HCO₃⁻/NO₃⁻ ratio < 10 and NO₃⁻ > 30 mg/L, it was possible to identify areas where aquifer recharge processes are clearly evident. These recharge processes are rapid, as confirmed by the hydraulic gradient, the high hydraulic conductivity of the aquifers, and further supported by the isotopic composition of groundwater, especially tritium concentrations. Furthermore, due to the hydrogeological characteristics of the surveyed region, which resemble those of alluvial basins in close proximity to mountain ranges, the methodology and findings of this study can be used as an unconventional and expedited method for similar research conducted globally, offering hope for the future of groundwater research. Full article

This article presents a methodological framework for evaluating hydrodynamic loading on seabed structures in the eastern Mediterranean, originally motivated by the design requirements of special protective structures for a planned high-voltage subsea interconnection between Crete and the Greek mainland. The associated study highlighted the need for a comprehensive evaluation of hydrodynamic loading on seabed structures in the South-East Mediterranean. A methodology is presented for determining representative design kinematics near the seabed, accounting for large-scale oceanic circulation, local wind-induced currents, wind-generated surface waves, and tsunami effects. The method integrates long-term metocean datasets, spectral wave modelling, and reliability-based combinations of critical processes, with adjustments for anticipated climate change impacts. The approach is demonstrated through two case studies involving an electrode protective cage and a submarine electricity transmission cable, both representative of components in subsea power connections. The analysis provides design values of velocities, accelerations, and hydrodynamic forces, with typical checks against sliding, uplift, and vibration. Results highlight the depth-dependent magnitude interplay between ocean circulation and wave-induced particle motions, as well as the importance of biofouling and marine growth. The findings aim to support the safe and sustainable design of offshore energy infrastructure in the eastern Mediterranean and similar marine environments. Full article

Old urban districts, characterized by complex drainage networks, heterogeneous surfaces, and high imperviousness, are particularly susceptible to flooding during extreme rainfall. In this study, the moat drainage district of Xi’an was selected as the research area. A refined hydrologic–hydrodynamic simulation and an assessment of drainage and flood-retention capacities were conducted based on the coupled GAST–SWMM model. Results show that the model can accurately capture the rainfall–surface–pipe–river interactions and reproduce system responses under different rainfall intensities. The box culvert’s effective regulation capacity is limited to 1- to 2-year return periods, beyond which overflow rises sharply, with overflow nodes exceeding 80% during a 2-year event. The moat’s available storage capacity is 17.20 × 10⁴ m³, sufficient for rainfall events with 5- to 10-year return periods. In a 10-year return period event, the box culvert overflow volume (12.56 × 10⁴ m³) approaches the upper limit, resulting in overtopping. These findings provide a scientific basis for evaluating drainage efficiency and guiding flood control management in old urban districts. Full article

Macroscopic fatigue tests, mesoscopic finite element simulations, and microscopic molecular dynamics simulations were composed to study the damage and failure of drainage asphalt mixtures in multiscale. The applicability of the fatigue models fit by strain, stress, and the linear fitting slope of the indirect tensile modulus curves were compared. The mesoscopic damage and failure distribution and evolution characteristics were studied, considering the single or coupling effect of traffic loading, hydrodynamic pressure, mortar aging, and interfacial attenuation. The microscopic molecular mechanism of the interface adhesion failure between the aggregate and mortar under water-containing conditions was analyzed. Results show that the fatigue model based on the linear fitting slopes of the indirect tensile modulus curves has significant applicability for drainage asphalt mixtures with different void rates and gradations. The damage and failure have an obvious leap development when traffic loading increases from 0.7 MPa to 0.8 MPa. The hydrodynamic pressure significantly increases the stress of the mortar around the voids and close to the aggregate, promoting damage development and crack extension, especially when it is greater than 0.3 MPa. With the aging deepening of the mortar, the increase rate of the damage degree gradually decreases from the top to the bottom of the mixture. With the development of interfacial attenuation, the damage and failure of interfaces continue increasing, while that of the mortar increases first and then decreases, which is related to the loading concentration in the interface and the stress decrease in the mortar. Under the coupling effects, whether the cracks mainly generate in the mortar or interface depends on their damage degrees, thus causing the stripping of the aggregate wrapped or not wrapped by the mortar, respectively. The van del Waals force is the main molecular effect of interface adhesion, and both acidic and alkaline aggregate components significantly tend to form hydrogen bonds with water rather than asphalt, thus attenuating the interface adhesion. Full article

Residual oil (RO) in terrigenous reservoirs formed after waterflooding can exceed 60% of the original oil in place; approximately 70% is trapped at the macro-scale in barriers and lenses, whereas about 30% remains at the micro-scale as film and capillary-held oil. This review aims to synthesize current knowledge of RO formation mechanisms, localization methods and chemical recovery technologies. It analyzes laboratory, numerical and field studies published from 1970 to 2025. The physical and technological factors governing RO distribution are systematized, and the effects of heterogeneities of various types, imperfections in pressure-maintenance (waterflood) systems and contrasts in oil–water properties are demonstrated. Instrumental monitoring techniques—vertical seismic profiling (VSP), well logging (WL), hydrodynamic well testing (WT) and geochemical well testing (GWT)—are discussed alongside indirect analytical approaches such as retrospective production-data analysis and neural-network forecasting. Industrial experience from more than 30,000 selective permeability-reduction operations, which have yielded over 50 Mt of additional oil, is consolidated. The advantages of gel systems of different chemistries are evaluated, and the prospects of employing waste products from agro-industrial, metallurgical and petroleum sectors as reagents are considered. The findings indicate that integrating multi-level neural-network techniques with instrumental monitoring and adaptive selection of chemical formulations is crucial for maximizing RO recovery. Full article

Coastal boulder deposits (CBDs) are among the most striking geomorphic signatures of extreme wave activity, recording the action of both tsunamis and severe storms. Their significance extends beyond geomorphology, providing geological archives that capture rare but high-impact events beyond the scope of instrumental or historical records. This review critically examines the origins, emplacement mechanisms, diagnostic morphology, monitoring tools, and global case studies of CBDs with the aim of clarifying the storm–tsunami debate and advancing their application in coastal hazard assessment. A systematic literature survey of 77 peer-reviewed studies published between 1991 and 2025 was conducted using Scopus and Web of Science, with inclusion criteria ensuring relevance to extreme-wave processes, geomorphic analysis, and chronological methods. Multiproxy approaches were emphasized, integrating geomatics (RTK-GPS, UAV-SfM, TLS, LiDAR), geochronology (¹⁴C, U–Th, OSL, cosmogenic nuclides, VRM), and hydrodynamic modeling. Findings show that tsunamis explain the largest and most inland megaclasts, while modern storms have proven capable of mobilizing boulders exceeding 200 t at elevations up to 30 m. Many deposits are polygenetic, shaped by successive high-energy events, complicating binary classification. CBDs emerge as multifaceted archives of extreme marine forcing, essential for refining hazard assessments in a changing climate. Full article