Search Results (3,287)

Jiaodong Peninsula is one of the regions with the most abundant medium–low-temperature convective geothermal resources in the eastern coastal area of China. Analyzing geothermal fluid characteristics can help understand its hydrochemical discharge characteristics and renewal capacity, and these characteristics also exhibit distinct geochemical symmetry that reflects the genesis and evolution of geothermal systems. In this study, we conducted a water quality analysis of 15 natural hot spring geothermal fluids, as well as their adjacent bedrock and Quaternary water, in the Jiaodong Peninsula. We measured deuterium and oxygen isotopes, and the γ Na/γ Cl and γ SO₄/γ Cl ratios of geothermal fluids, focusing on the geochemical symmetry of these indicators to reveal the evolutionary rules of geothermal fluids. The hydrochemical types of geothermal fluids in the Jiaodong Peninsula included Cl–Na, Cl–Na·Ca, HCO₃·SO₄–Na, and SO₄·HCO₃–Na, with mineralization degrees of 0.45–7.68 g/L and pH values of 7.3–8.63. The geothermal fluid primarily originated from the infiltration recharge of atmospheric rainfall and had no hydraulic connection with the shallow Quaternary water and adjacent bedrock water near the geothermal field. The geothermal fluid in the study area had not yet reached water–rock equilibrium. For geothermal fields with higher γ Na/γ Cl and γ SO₄/γ Cl ratios, the corresponding geothermal fluid circulation depth was relatively shallow, indicating a poorly sealed hydrodynamic environment with strong renewal capacity, where the geothermal fluid is in a continuous supply–runoff–discharge process. The γ Na/γ Cl and γ SO₄/γ Cl ratios of some geothermal fields were close to those of seawater; this symmetric difference was caused by the large circulation depth and long residence period of the geothermal fluid, which had experienced a high degree of decarbonization. Our findings on the hydrochemical characteristics and geochemical symmetry of medium–low-temperature geothermal fluids in the Jiaodong Peninsula will help deepen the understanding of the formation and evolutionary mechanism of this type of geothermal resource. Full article

Water scarcity is increasingly recognized as a slow-onset ecological crisis with major environmental, socio-economic and governance effects, yet systematic assessments of how research on this topic has evolved remain limited. This study addresses this gap through a bibliometric and thematic analysis of water-scarcity publications from 2000 to 2025, using VOSviewer (version 1.6.20), Biblioshiny™ (Bibliometrix version 4.3.1) and RStudio (version 2024.12.1 + 563) to map research trends, conceptual clusters and leading contributing countries, institutions and authors. The analysis shows that water scarcity research is organized around four dominant themes: adaptive water management and climate resilience, plant physiological responses to drought and water stress, ecosystem resilience and biodiversity under water scarcity, and water-limited agriculture and food security. Early scholarship focused heavily on biophysical processes such as drought tolerance and hydraulic conductivity, while recent studies increasingly incorporate socio-ecological, governance and policy dimensions, reflecting a shift toward holistic, solution-oriented approaches. Overall, the study provides a comprehensive overview of the evolution and global distribution of water scarcity research, highlighting the importance of integrating biophysical knowledge with human-centered strategies to support evidence-based decision-making, strengthen inclusive water governance, and enhance socio-ecological resilience in the face of a changing climate. Full article

Slug test interpretation can fail when measured recovery follows a time scale that differs from the classical Cooper–Bredehoeft–Papadopulos (CBP) finite-diameter well solution. This study derives a conformable slug test formulation by showing that a local weighted derivative converts the governing problem into the classical solution evaluated in transformed time. The formulation therefore does not introduce a nonlocal memory kernel; instead, it provides a reproducible diagnostic with one fitted exponent for testing power law time scaling while retaining the finite-diameter wellbore storage boundary condition. The solution is evaluated using double-precision Stehfest numerical inversion with 12 terms and is verified by the exact classical limit and by sensitivity tests on the number of inversion terms. Type curves, Morris sensitivity indices, objective function slices, synthetic benchmarks, and measured slug test data from the Minnelusa and Madison aquifer system near Spearfish, South Dakota, are used to evaluate the added exponent. A benchmark with an exponent above one recovered fitted exponents of 1.397 without noise and 1.417 under Gaussian noise with a standard deviation of 0.01. Field fitting over exponents from 0.5 to 2.0 reduces root mean square error and information criteria relative to the classical model for the analyzed datasets, especially the LA-88B pressure tests. However, exponents above one are interpreted only as accelerated transformed time behavior, not as conventional fractional orders or unique physical mechanisms. Comparison with a published semi-analytical slug test model that represents near-well formation damage and non-Darcy flow for the same field dataset supports using the conformable exponent as a diagnostic indicator of time-scale mismatch alongside mechanistic slug test models. Full article

Exhaust piping in diesel engines is subject to severe thermal stress arising from high-temperature, high-pressure gas flows, and spray cooling with atomizing nozzles has become a widely adopted method to safeguard structural reliability. However, at present, the understanding of the spray fragmentation mechanism of two-phase flow under low inlet pressure is still not comprehensive. This study establishes a three-dimensional model of a gas–liquid impinging-jet nozzle and applies a coupled Volume-of-Fluid to Discrete-Phase-Model (VOF–DPM) approach to resolve the liquid breakup process in detail. High-speed imaging experiments were carried out to validate the numerical results. Orthogonal tests were conducted at five pressure levels for both gas and water—0.28, 0.24, 0.20, 0.16, and 0.12 MPa—producing 25 data pairs of spray cone angle and Sauter Mean Diameter (SMD). Within the 0–0.3 MPa air inlet pressure range explored here, raising the pressure consistently reduced the SMD and widened the cone angle, although both trends weakened as the pressure increased. Water inlet pressure exhibited a nonlinear influence, with local extrema appearing in the higher-pressure region. The overall SMD reached a minimum of 34.12 μm and a maximum of 149.04 μm. Using these 25 data points, a genetic algorithm was employed to optimize the pressure ratio under the constraint of total hydraulic power, yielding optimization strategies for different power budgets. An additional outcome of the simulation was the identification of a structural weakness: by reshaping the original flat impingement surface into a full conical surface, atomization quality improved by 29.36% under identical boundary conditions. These findings clarify the atomization mechanism of gas–liquid impinging jets under low inlet pressure and offer practical guidance for nozzle optimization. Full article

In the face of the raw materials crisis and environmental concerns, sustainable waste management has become a priority for current and future generations. Recycling waste from wastewater treatment plants in a closed loop protects natural resources, reduces landfill volumes, and lowers disposal costs. This paper presents the results of tests on the physical, filtration, and mechanical properties of mixtures of washed mineral waste (WMW) from grit chambers with fly ash from the thermal treatment of municipal sewage sludge (SSA) in a fluidized bed furnace. Additionally, radiological tests of the mixture components were conducted. Based on the conducted tests, the possibility of sustainable use in civil engineering, such as soil backfills and embankment construction materials, was assessed. The possibility of safely using waste materials in the indicated construction solutions was demonstrated for mixtures with dominant WMW content (90% and 70% by total weight). The waste mixtures correspond to poorly or medium-grade sands with a small amount of silt (uniformity coefficients of 3.33, 3.50, and 8.00). They are characterized by maximum dry densities of 1.542, 1.770, and 1.780 g/cm³; optimal moisture contents of 12.54, 12.86, and 20.25%; permeability coefficients of 0.08, 0.22, and 0.39 m/d; and internal friction angles of 38.4, 39.5, and 40.1°. The values of the determined parameters of some mixtures are similar to those of natural sands used as construction aggregates. All mixtures meet the geotechnical criteria for use in road embankments, below frost depth, and in flood embankment bodies. Mixtures with a 90% mass fraction of WMW were also approved for application as backfill for installation trenches. However, none of the mixtures met the hydraulic conductivity threshold required for the upper layers of embankments nor for backfill of abutments and retaining structures without the use of an additional binder (cement or lime), which is considered a prerequisite for these applications. Full article

Natural lateral particle segregation commonly occurs during the hydraulic deposition of slurry and thickened tailings in surface tailings storage facilities (TSFs), producing spatial heterogeneity in physical, hydrogeotechnical, and mineralogical properties, as well as in the water table. In sulfide-rich tailings, such heterogeneity complicates the design of reclamation cover systems, which are themselves affected by it. This study investigates the impact of physical and rheological properties of hard-rock mine tailings slurries on their segregation under hydrodynamic conditions. It proposes a multiparametric equation for the segregation index (SI) based on Buckingham’s π theorem. For this purpose, six flume experiments were conducted using tailings with initial solid mass concentrations of 63%, 66%, and 69% at slopes of 0.5% and 1%. Results revealed strong exponential correlations (R² > 0.95) between SI and tailings’ physical properties (solid concentration, bulk density) as well as rheological parameters (Herschel–Bulkley yield stress and flow index, Cross infinite dynamic viscosity). The SI equation was developed using MATLAB R2025b nonlinear least-squares optimization with a trust-region reflective algorithm. Using an SI threshold of 0.05 to define non-segregating behavior, the proposed model can predict segregation tendencies as a function of tailings properties and slope conditions. Further laboratory and field investigations are needed to validate and generalize the criterion. Full article

Borate-crosslinked hydroxypropyl guar (HPG) gels are widely used as water-based fracturing fluids in oilfield stimulation. During hydraulic fracturing, their effectiveness depends on the rapid formation of a low-permeability filter cake on fracture walls, which helps reduce fluid invasion, maintain fracture pressure, and support fracture propagation. In high- and ultra-high-permeability reservoirs, however, rapid matrix invasion may occur faster than effective filter-cake formation, causing severe pre-cake spurt loss or even uncontrolled leakoff. Conventional filter-paper tests tend to emphasize stabilized wall-building behavior and may therefore fail to represent the early-time spurt loss in porous reservoir media. In this study, the leakoff behavior of borate-crosslinked HPG fracturing fluids was investigated using a modified static fluid-loss apparatus. Experiments were conducted at differential pressures of 0.5–6.0 MPa through filter paper and artificial sandstone disks with permeabilities from 0.120 to more than 4.0 μm². The filter-paper tests showed typical wall-building behavior, with limited spurt loss and stable late-time leakoff. In contrast, the sandstone-disk tests revealed a transition from cake-controlled leakoff to early-time spurt-loss-dominated leakoff as permeability and differential pressure increased. When permeability exceeded approximately 1.55–2.42 μm², spurt loss (V_sp) became the main contributor to total leakoff, whereas the late-time wall-building coefficient (C_w) was much less sensitive to permeability. This indicates that permeability mainly controls the pre-cake invasion stage rather than the stabilized leakoff stage. Based on these results, an empirical spurt-loss model considering permeability and pressure differential was developed, and spurt-loss zoning maps were constructed for engineering evaluation. Limited ultra-high-permeability tests further showed that quartz particles promoted early bridging and reduced leakoff under moderate pressure differentials, but the particle-assisted barrier lost effectiveness under higher pressure differentials. These findings demonstrate that filter-paper-based criteria are insufficient for evaluating HPG gel performance in extreme-permeability formations and that a spurt-loss-based framework is needed for fluid-loss-control design and fracturing-fluid selection in high-permeability reservoirs. Full article

The localized high hydraulic gradient at the bottom of concrete cutoff walls in deep overburden foundations poses a significant seepage failure risk. This stability is heavily influenced by the high-stress state, a critical factor often overlooked in conventional evaluations. Taking a specific engineering project as the research background, this study investigates the seepage stability of gravelly medium-coarse sand by simulating the coefficient of earth pressure at rest (K₀) condition. A comprehensive series of triaxial seepage tests was conducted across burial depths from 120 m to 260 m, supplemented by conventional zero-stress permeability tests as a baseline. The results indicate that the seepage failure mode is characterized by overall soil flow. For soil deeply buried at the wall bottom, the risk of seepage failure is relatively low, provided there are no significant geological defects or internal seepage outlets nearby. Compared to conventional tests, the K₀ stress condition significantly increases the failure gradient and reduces the permeability coefficient. Under the same gradation, variations in burial depth have a negligible influence on these parameters. However, at the same burial depth, particle gradation has a major effect; the mean envelope line is the most sensitive to stress, followed by the upper and lower envelope lines. Based on these findings, an allowable hydraulic gradient of 3.0 is proposed—approximately five times the traditional design value (0.6–0.65). This study provides a critical scientific basis for the seepage-control design and stability assessment of high dams on deep overburden foundations. Full article

Managed aquifer recharge (MAR) is increasingly being realized as an important approach to improve water security in arid and semi-arid environments where there is a low amount of surface water and high climatic variability. This paper introduces a unified approach to the process of locating appropriate MAR locations and estimating recharge potential in Central Kazakhstan through a multi-criteria analysis using geographic information systems (GIS) and hydrogeological field exploration, water balance modelling. Remote sensing datasets and evapotranspiration (ET) analyses were conducted for the 2014–2024 period, while field investigations, infiltration tests, and hydrochemical sampling were performed during the 2025 field campaign. The suitability testing was preliminarily performed in the Google Earth Engine (GEE; Google LLC, Mountain View, CA, USA) environment as a weighted overlay test with the combination of terrain, vegetation, hydrological, and land cover parameters. According to the suitability map obtained and patterns of activity in agricultural activities, eleven candidate sites were identified, out of which eight were found to be suitable after hydrochemical analysis. The Nesterov and Boldyrev techniques of field-based infiltration tests produced a range of 0.05 to 1.42 m/day of hydraulic conductivity. Water balance analysis shows that the total amount of water that could potentially be added to groundwater recharge is about 40.2 million m³/year and that the effective amount of water could be recharged is about 11.0 million m³/year, which is limited by the infiltration processes. This means that about 27 percent of the available water is added into ground water recharge, which is a significant boost to the original estimates. The assessment of the storage capacity of the aquifers indicates that at all locations, the pore space is much greater than the recharge volumes that have been calculated and, therefore, storage is not a limiting factor in the implementation of MAR. It is estimated that the potential MAR rates range between 174 and 5282 m³/day depending on local hydrogeological conditions. The suggested method offers a powerful and generalizable site selection and measurement framework of MAR in arid areas with limited data. The findings highlight the significance of combining remote sensing, field measurements, and process-based modeling to aid sustainable groundwater management and climate adaptation strategies. Full article

The rapid growth in the electric vehicle sector has increased demand for advanced battery thermal management systems (BTMSs) with high heat-dissipation capacity and temperature uniformity. Immersion cooling using dielectric fluids has recently been recognized as a promising alternative technology to conventional indirect liquid cooling methods. This study investigates the thermal and hydrodynamic behaviour of a sixteen-lithium-ion cell battery (LIB) module immersed in low-viscosity dielectric fluids using three-dimensional computational fluid dynamics simulations. In this context, a total of twenty dielectric fluids are evaluated using the ANSYS Fluent solver, with particular emphasis on the effects of key thermophysical properties, including viscosity, density, specific heat capacity, and thermal conductivity. The simulation findings reveal that mineral oil and PAO4 yield the lowest maximum LIB cell temperatures, with a reduction of approximately 4 K compared to the least effective dielectric fluids, such as undecane and cumene. Moreover, in terms of temperature uniformity, mineral oil, Novec 7000, and PAO4 exhibit the most homogeneous temperature distributions among the twenty dielectric fluids. In addition, they show an improvement in the temperature uniformity index of approximately 32.4% compared with the least effective dielectric fluid, cumene. On the other hand, mineral oil and PAO4 generate significantly higher pressure drops because of their relatively high viscosities, which increases hydraulic resistance and pumping power requirements. These findings demonstrate that excellent thermal performance does not necessarily correspond to optimal overall thermo-hydraulic behaviour. Overall, the results confirm that immersion-BTMS performance is governed by a complex interaction between dielectric fluid thermophysical properties and flow behaviour, highlighting the importance of coupled thermo-hydraulic optimization in the selection of dielectric fluids for next-generation immersion-cooled battery systems. Full article

The brake–release stability of electro-hydraulic thrusters (EHTs) significantly affects the safety of hydraulic braking systems, especially under low-temperature conditions with varying fluid viscosity. Most existing studies have focused on macroscopic braking characteristics, while the internal flow field variation and vortex evolution mechanism during the brake–release process remain insufficiently explored. In this work, transient CFD simulations are conducted to investigate vortex formation rules and flow field characteristics inside an EHT. Three typical vortex structures denoted as α, β, and γ are identified, and the independent and coupling influences of fluid dynamic viscosity and motor speed on vortex intensity and piston-bottom pressure are quantitatively analyzed. The results show that vortices α and β trigger flow disorder and additional hydraulic energy loss, while vortex γ optimizes flow uniformity and assists piston extension. Higher fluid viscosity exacerbates vortex development and pressure fluctuation, while increasing motor speed accelerates transient flow field evolution. This study clarifies the internal flow mechanism of EHT brake–release behavior and provides reliable parametric guidance for optimizing the low-temperature performance of electro-hydraulic braking systems. Full article

Local scour and vortex-induced vibrations around cylindrical structures in curved channels pose significant risks to the safety and stability of critical hydraulic infrastructure, such as bridge piers. To address these engineering challenges and elucidate the underlying flow mechanisms, this study conducts numerical simulations of flow past two side-by-side circular cylinders of equal diameter in a curved channel under subcritical conditions at Re = 3900, using the Realizable kε turbulence model. Spectral Proper Orthogonal Decomposition (SPOD) is introduced to quantitatively characterize the energy distribution and dominant coherent structures. Taking the spacing ratio L/D and the placement angle α as key design parameters, the flow field characteristics, modal energy distribution, and coherent structure evolution are systematically investigated for two side-by-side cylinders in three-dimensional straight and curved channels. The numerical results show that, in the straight channel, as L/D increases from 2 to 4, the flow field evolves from strong coupled interference to weak interaction. The vortex shedding frequency structure evolves from a single dominant frequency to a multi-frequency distribution with rich harmonic components, indicating a transition in wake dynamics from energy concentration to multimodal dispersion, accompanied by a significant improvement in flow stability. Under curved channel conditions, the results reveal an asymmetric flow field caused by pronounced energy concentration on the inner side of the channel. SPOD analysis further indicates that as the placement angle α increases from 30° to 90°, the modal energy distribution changes from concentrated to dispersed, the frequency spectrum broadens with enhanced harmonic components, and flow instability gradually intensifies. Overall, the spacing ratio L/D mainly governs the wake-interference pattern, whereas the placement angle α regulates the frequency structure and energy distribution. Among all the cases investigated, relatively favorable flow stability is achieved at L/D = 4 and α = 30°. The SPOD-derived modal energy distributions show that the streamwise fluctuation length of the dominant-mode energy is approximately 0.25 m at α = 30°, compared with 0.5 m at α = 90°, with the energy bandwidth nearly doubling. The combined CFD-SPOD approach effectively captures energy evolution and coherent structure characteristics of complex flows across spatial, temporal, and spectral dimensions. This enables a shift from conventional flow-field description to frequency-based mechanism analysis and provides a theoretical basis for structural layout optimization and scour protection in hydraulic engineering. Full article

Background/Objectives: Changes in the mechanical behavior of orthodontic archwires during clinical use are not fully understood, particularly when different bracket systems are employed. Self-ligating (SL) brackets have gained considerable popularity in orthodontic practice in recent years, largely due to claims of improved treatment efficiency and biomechanical performance. Nevertheless, current evidence has not consistently demonstrated statistically significant differences between conventional ligation (CL) brackets and SL systems. The aim of this study was to evaluate changes in the mechanical properties and degradation over time of nickel-titanium (NiTi) archwires after clinical use in orthodontic treatments performed with CL and SL brackets. Methods: A comparative study was conducted using archwires retrieved from orthodontic patients. Round 0.014-inch NiTi wires (GC Orthodontics America Inc., IL, USA) were analyzed. The archwires were used in 60 patients treated with either CL or SL appliances and evaluated at four time points: before clinical use (T0), and after 1 month (T1), 2 months (T2), and 3 months (T3) of intraoral service. Mechanical testing was performed according to ISO 15841:2014 + Amd. 1:2020 using a three-point bending test with a universal testing machine (Z005 Test Control II Universal Testing Machine, Zwick Roell, Kennesaw, GA, USA). The variables analyzed included the mean force delivered by the archwires at deflections of 3 mm (F3), 2 mm (F2), 1 mm (F1), and 0.5 mm (F0.5), as well as the slope of the superelastic plateau at 2 mm, 1 mm, and 0.5 mm. The static and dynamic friction coefficients, as well as the friction forces associated with the wires and the two types of brackets, were determined using a modified MTS-Bionix servo-hydraulic testing machine. The tests were conducted at 37 °C in a saline environment. Results: Both groups showed changes in the superelastic behavior of NiTi archwires. Alterations increased with longer intraoral exposure. In the SL group, significant modifications were already observed after one month of clinical use, with a reduction in the force delivered and a loss of superelastic characteristics. These changes remained relatively stable thereafter, with no statistically significant differences during the following months. In contrast, the CL group showed a progressive reduction in force delivery and superelasticity over time. This is due to the difference in friction between the wire and the CL bracket compared to the SL bracket, which results in greater force transfer for tooth movement. Conclusions: Overall, differences in the mechanical behavior of archwires between CL and SL systems were observed during the initial stages of clinical use. However, these differences diminished over time, and no significant differences were detected after three months. Considering the progressive degradation of mechanical properties, the reuse of archwires that have remained intraorally for more than three months may not be advisable. Full article

The underground caverns of pumped-storage power stations generally feature large inclination angles. During the bottom-up oblique excavation by hard-rock Tunnel Boring Machines (TBMs), the Anti-Back-Slip (ABS) support system is the core device ensuring safe operations. Specifically, the synchronization of the multiple hydraulic cylinders within the ABS system is a critical factor determining the stability and safety of the TBM. Therefore, this paper designs a hydraulic control system for the ABS device and proposes an adjacent cross-coupling synergistic control strategy based on adaptive backstepping. This strategy innovatively integrates an adaptive backstepping control law into the adjacent cross-coupling topology to achieve high-precision multi-cylinder control. Utilizing the AMESim-Simulink platform, high-fidelity co-simulations are conducted under both uniform and eccentric load conditions. The results demonstrate that under nominal conditions, the proposed algorithm exhibits asymptotic convergence at the mathematical level. The system maintains robust stability under dynamic excitations. When subjected to sudden asymmetric eccentric loads of 1.0–2.0 times, the system prevents tracking divergence and limits the maximum multi-cylinder synchronization error to within 1.82 mm. This research satisfies the requirements for synchronous control and provides a theoretical and engineering reference for the disturbance-rejection synergy of inclined shaft TBM support systems. Full article

Various hydraulic automatic gates play an important role in water resources regulation. This study proposes a novel suspended hydraulic automatic control gate for tidal marine energy generation with adaptive one-sided flow-through characteristics. To evaluate its hydraulic performance and regulation mechanism, model experiments were conducted in a laboratory flume under different upstream and downstream water levels and discharge conditions. Gate opening states, hydraulic parameters, and flow field structures were obtained, while computational fluid dynamics simulations were used to reproduce and analyze the experimental flow field. The results show that the gate opening angle and water level jointly control the discharge capacity, and significant differences exist in the flow structure and discharge behavior between free and submerged outflow conditions. The numerical model further reveals vortex structures, velocity stratification, and gas–liquid two-phase distributions near the gate. Variations in gate structural parameters, discharge, and downstream water level significantly affect moment equilibrium, flow regime, and discharge capacity. The proposed discharge formula effectively predicts variations in gate flow and force characteristics under different hydraulic conditions, showing good applicability and engineering value. The suspended hydraulic automatic control gate has a simple structure, strong adaptability, and promising potential for tidal water regulation and engineering applications. Full article