Search Results (1,296)

This study investigates the hydrodynamic characteristics of single-layer heave plates with varying salient edges and triple-layer configurations with size mismatches under forced oscillation, utilizing 3D overset mesh numerical simulations. For single-layer plates, the 0° edge configuration maintains high hydrodynamic coefficients across all conditions, whereas the 135° edge peaks under specific parameters. Introducing horizontal gaps consistently degrades performance. For triple-layer plates, increasing the spacing ratio mitigates spatial flow interference, significantly enhancing hydrodynamic coefficients. Furthermore, introducing size differences creates a stepped mismatched configuration that effectively mitigates wake shielding and enhances fluid entrainment. Consequently, the coefficients increase steadily with the absolute size difference, reaching optimal heave suppression in the triple-layer arrangement with a large spacing and a ±20 m size mismatch. Finally, a highly accurate empirical formula (R² > 0.92) is proposed to predict the damping (C_d) and added mass (C_a) coefficients, effectively capturing the nonlinear coupling effects of spacing ratio and size difference. These findings provide practical theoretical guidance for optimizing vibration reduction systems in offshore platforms. Full article

Extreme hydrological events fundamentally alter sediment transport dynamics across grain, reach, and watershed scales, rendering classical equilibrium-based transport formulations inadequate. This review synthesizes recent advances in multiscale sediment transport modeling under highly unsteady and high-magnitude forcing conditions. At the grain scale, particle-resolved simulations demonstrate that sediment entrainment is governed by turbulence intermittency and transient force exceedance rather than mean bed shear stress thresholds, particularly when the hydrograph rise timescale (T_h) becomes comparable to particle response times (T_p). At the reach scale, non-equilibrium transport emerges when the unsteadiness ratio T_h/T_a∼O(1), where T_a is the sediment adaptation timescale representing the time required for sediment flux to adjust toward transport capacity. Under these conditions, pronounced hysteresis between discharge and sediment flux is observed, requiring relaxation-based transport formulations instead of instantaneous equilibrium laws. At the watershed scale, the sediment delivery ratio (SDR), defined as the ratio of sediment yield at the basin outlet to total hillslope erosion, becomes highly time-dependent. Extreme precipitation events can activate hillslope-channel connectivity, increasing SDR by orders of magnitude relative to baseline conditions. A unified dimensionless scaling framework is presented based on mobility intensity (θ/θ_c, where θ is the Shields parameter and θ_c is its critical value for incipient motion), unsteadiness ratio (T_h/T_a), and morphodynamic coupling (T_f/T_m, where T_f is the hydraulic advection timescale and T_m is the morphodynamic adjustment timescale). This framework enables classification of sediment transport regimes ranging from quasi-equilibrium to cascade-dominated states. The synthesis demonstrates that predictive uncertainty increases nonlinearly across scales due to timescale compression, threshold activation, and feedback between flow hydraulics and evolving morphology. Recent developments in hybrid physics-AI approaches show promise in improving predictive capability by enabling dynamic transport closures, surrogate modeling of computationally expensive microscale processes, and data assimilation for real-time forecasting. However, these approaches remain limited by extrapolation uncertainty and the need to enforce physical constraints. Overall, this review concludes that regime-aware multiscale coupling, combined with uncertainty quantification and adaptive modeling strategies, is essential for robust sediment hazard prediction and climate-resilient infrastructure design under intensifying hydrological extremes. Full article

While check dams are crucial for debris flow mitigation, they face increasing failure risks under extreme weather and seismic activities. Their collapse can severely amplify debris flow magnitude, yet quantitative understanding of this amplification mechanism remains limited. Based on field investigations in southern Gansu, China, and a total of 12 flume experiments (comprising 11 distinct scenarios and 1 representative repeatability test), this study quantitatively assesses the amplification effect of dam breaches under varying channel slopes, check dam types, and bed conditions. Results indicate that dam-breach debris flow evolution comprises three stages: material initiation and deposition, breaching and material release, and recession. Crucially, dam breaching shifts the initiation mode from progressive retrogressive erosion to a near-instantaneous release of mass and potential energy. Compared to no-dam scenarios, breaches amplified peak discharge, erosion rate, and downstream inundated area by factors of 1.65–3.04, 1.44–1.55, and 2.14–2.77, respectively. This amplification is driven by the rapid initial release of material and energy, compounded by erosional entrainment during the transport phase. Furthermore, check dam type and channel slope act as key controlling factors. By revealing how check dams transition from protective structures to hazard sources, this study provides quantitative experimental evidence for optimizing dam design and advancing resilient disaster risk reduction strategies in mountainous regions. Full article

The growing volume of construction and demolition waste has made discarded concrete a major source of urban solid waste, placing increasing pressure on land resources and the environment. Recycling waste concrete into recycled aggregate concrete (RAC) offers an effective solution for resource conservation and carbon reduction, aligning with the goals of sustainable development. However, due to the residual mortar, high porosity, and microcracks of recycled aggregates, RAC generally exhibits lower compactness, strength, and durability than conventional concrete, particularly under freeze–thaw conditions where degradation accelerates and service life decreases. To address these challenges, this study investigates the optimization of RAC mix design and its frost resistance performance for pavement base applications. An orthogonal experimental design was employed, with the water-to-binder ratio, recycled aggregate replacement ratio, and air-entraining agent dosage as key variables, while 7-day compressive strength, permeability coefficient, and rebound modulus served as evaluation indices. The influence and interaction of these factors were analyzed to determine an optimal mix meeting both mechanical and durability requirements. Rapid freeze–thaw cycling tests were then conducted to examine the variations in mass loss, relative dynamic modulus, and compressive strength retention, followed by exponential and damage variable modeling to characterize the degradation process. Results show that the water-to-binder ratio primarily governs strength, the replacement ratio affects stiffness and permeability, and the air-entraining agent significantly enhances frost resistance by improving pore structure. The optimized mix retained over 70% of its relative dynamic modulus after 300 freeze–thaw cycles, exhibiting superior durability. This work establishes a systematic framework for multi-factor optimization and durability evaluation of RAC, providing theoretical and practical guidance for its application in cold-region pavement bases. Full article

The Burullus–Baltim coastal zone of Egypt’s Nile Delta represents a critical geoheritage sand-dune system functioning as the primary natural defense line against inundation of the central Nile Delta. This ecosystem is increasingly threatened by intensive black sand mining, raising concerns regarding long-term coastal sustainability. Black sand extraction disrupts dune integrity by reducing sediment density and heavy mineral content, thereby lowering resistance to wind forcing and accelerating aeolian transport. This study assesses historical dune migration and extraction-driven changes in aeolian dynamics using high-resolution satellite imagery, ERA5 wind reanalysis (1975–2024), and integrated analytical–numerical modeling, with implications for sustainable coastal management. A dominant northwesterly wind regime drives eastward and southward dune migration of 3.22 m/yr and 1.7 m/yr, respectively (2010–2025). Black sand mining since 2022 has measurably reduced heavy mineral content and bulk density, altering grain-size distribution and making dunes significantly more susceptible to wind entrainment. Coupled Bagnold and AeoLiS modeling predicts an 8.21% rise in mass transport rates and a corresponding acceleration in dune migration following extraction. These findings demonstrate that black sand mining amplifies aeolian transport and increases sand encroachment risks to nearby settlements, infrastructure, and agricultural lands. The results highlight the trade-offs between resource extraction and coastal dune ecosystem services, particularly flood protection and land stability, emphasizing the need for regulated mining, bioengineered dune stabilization, and predictive modeling to enhance the Nile Delta’s long-term resilience. Full article

To address the challenges of complex wellbore trajectories in horizontal gas wells and the significant differences in droplet entrainment laws across various well sections, which make it difficult to accurately predict the most critical location for liquid loading, this study establishes a prediction model for the critical liquid-carrying flow rate in different well sections. The model is based on droplet force balance and Kelvin–Helmholtz wave theory, considering droplet deformation and energy losses due to wall collisions and friction. By integrating the critical liquid-carrying flow rate models for each section with a four-field coupled wellbore prediction model, a coupled temperature-pressure and liquid-carrying prediction model is developed. Sensitivity analysis was performed on factors influencing the critical liquid-carrying flow rate, and a field data analysis was conducted on 43 gas wells. The results indicate that the proposed model provides accurate predictions, with only one well being misjudged. For four wells near the liquid loading state, the predictions were within a ±15% error range, with an average deviation of only 5.9%. The research results provide a theoretical basis for the accurate prediction of liquid loading in horizontal gas wells. Full article

This study focuses on flame spread and merging in discrete fuel arrays composed of birch rods under dual fire source conditions. Tests were performed with five fuel spacings (nL/W = 1, 2, 3, 4, single source) and eight array spacings (S = 2 mm to 9 mm) to quantitatively evaluate the influence of these parameters on the flame merging behavior and key spread characteristics. The results indicate that the probability of flame merging decreases with increasing fuel spacing and is strongly affected by array spacing. Both the inter-fire temperature and dimensionless temperature rise were found to follow distinct power-law relationships with spacing. Flame height is governed by both spacing parameters. In contrast, the flame spread rate responded to array spacing but exhibited minimal sensitivity to fuel spacing. In this study, heat flux between the two arrays is demonstrated to be dominated by thermal radiation. A predictive model was formulated for the merged flame height, demonstrating close agreement with the experimental results. Full article

The hydrojet-shield machine, a rapidly advancing shield machine type, uses slurry for excavation and muck removal via a pipeline system. The pipeline includes a flushed feeding system that injects slurry into areas at risk of obstruction. This study provides a computational fluid dynamics (CFD) analysis of the flow characteristics of a large hydraulic shield machine, proposing the Particle Lifting Coefficient (L) and Regional Improvement Ratio (I) as innovative criteria to evaluate the effects of flow rate distribution and cutting wheel rotational velocity. By adjusting the proportion of scouring flow in the lower part of the chambers to 30%, 50%, and 100%, three flow distribution strategies, labeled as FC1, FC2, and FC3, were obtained to suit normal slurry transport conditions, address cutterhead mud accumulation, and deal with the deposition of rock and soil particles at the bottom of the chamber, respectively. The FC3 strategy amplifies the flow of symmetric jets in the lower scouring region, strengthening the upward flow that entrains surrounding fluid, thereby significantly increasing the L and I values in the targeted area and showing great potential for inhibiting the settlement and deposition of rock and soil debris. This study also emphasizes the need to integrate slurry jet distribution strategies with real-time monitoring of cutterhead mud accumulation and chamber deposition, while adjusting cutterhead rotation speed based on geological conditions. Full article

Background: Circadian disruption exacerbates type 2 diabetes mellitus (T2DM). Time-restricted feeding (TRF) and exercise (EX) improve metabolic health, but their combinatory effect remains unclear. This study investigated whether combined TRF and EX additively ameliorates metabolism via circadian reprogramming in db/db mice. Methods: Eight-week-old male db/db mice were assigned to control (Con), diabetic model (DM), TRF (8 h feeding window), EX (treadmill, 60 min/day, 5 days/week), or combined TRF + EX groups for 8 weeks (n = 8/group). Body weight, glucose/insulin tolerance, and 24 h energy metabolism (CLAMS) were assessed. Mitochondrial function, oxidative stress, inflammation, and expression of mitophagy (Pink1, Park2, Bnip3, Fundc1) and thermogenic (Ucp1, Pgc1a, Prdm16, Cidea) genes were measured. Results: Compared with the con group, DM mice showed obesity, hyperglycemia and blunted circadian metabolic rhythm. The TRF and EX groups improved these defects. Specifically, combined TRF + EX reduced fasting blood glucose from 25.3 ± 3.1 mmol/L (DM) to 13.2 ± 1.8 mmol/L (p < 0.05), body weight from 49.8 ± 2.5 g to 39.5 ± 1.7 g (p < 0.05), and body fat percentage from 45.6 ± 3.2% to 32.1 ± 2.2% (p < 0.05). GTT area under the curve (AUC) decreased from 3711.0 ± 186.5 (DM) to 2118.0 ± 112.4 (p < 0.05), and ITT AUC decreased from 2617.5 ± 135.8 to 1260.0 ± 68.9 (p < 0.05). Notably, the combination of TRF + EX produced greater effects than either intervention alone: body weight, fasting blood glucose, and glucose/insulin tolerance were greatly improved (p < 0.05). In addition, compared with the DM group, the diurnal metabolic amplitude and phase were improved in the TRF or EX group; the combination group showed further improvements in these parameters. Furthermore, TRF and EX each resulted in significantly higher expression of key thermogenic genes (Ucp1, Pgc1a, Prdm16, Cidea) in white adipose tissue (WAT) and brown adipose tissue (BAT) (p < 0.05), and the TRF + EX group showed the highest expression levels. Combined intervention also restored skeletal muscle SOD activity (31.2 ± 2.9 U/mg prot vs. DM 20.1 ± 2.5 U/mg prot, p < 0.05) and reduced serum TNF-α (28.5 ± 4.5 pg/mL vs. DM 65.8 ± 8.5 pg/mL, p < 0.05) and IL-6 (21.6 ± 3.8 pg/mL vs. DM 50.3 ± 7.1 pg/mL, p < 0.05). Conclusions: TRF + EX additively restores metabolic homeostasis in diabetes by re-entraining circadian energy rhythms, improving mitochondrial quality, and activating adipose thermogenesis, supporting further investigation of integrated lifestyle timing as a potential therapeutic strategy. Full article

Due to the high water absorption of coal gangue aggregate, concrete prepared with a high content of this material exhibits a significantly reduced service life under freeze–thaw conditions. This study evaluates the frost resistance of gel-enhanced coal gangue aggregate concrete modified by incorporating nano-SiO₂ and polypropylene fibre (PPF) to generate more C-S-H gel and form a dense structure with different dosages of air-entraining agent (0, 0.004%, 0.008%, 0.012%, and 0.016%). The research results show that when the admixture content is 0.012%, the concrete still exhibits excellent frost resistance after 100 freeze–thaw cycles. The mass loss is only 4.7%, compressive strength loss is 37%, and dynamic elastic modulus loss is 39%, while the specimen maintains the best apparent integrity. In addition, the capillary water absorption rate, initial capillary water absorption rate, and cumulative water absorption all reach their lowest values under this condition, indicating optimal frost resistance performance. Finally, through regression analysis, a highly accurate predictive model for capillary water absorption was established, providing a theoretical basis for further research on the durability and frost resistance of coal gangue aggregate concrete. Full article

Non-cohesive earth dams are widely distributed in natural and semi-engineering scenarios, and overtopping-induced breaches are their most catastrophic failure mode. Accurate prediction of the overtopping failure process and breach evolution is critical for risk assessment, emergency management, and dam design optimization. In this study, an improved 3D numerical method is developed to simulate the coupled hydrodynamic–erosion–breach evolution processes of non-cohesive earth dams. The model based on the finite volume method integrates three core modules: a hydrodynamic module based on the Reynolds-Averaged Navier–Stokes equations with the Volume of Fluid method for free surface tracking, a dam material erosion module considering particle entrainment and transport mechanisms of non-cohesive soils, and a breach development module coupling erosion and gravitational collapse. To validate the model, two levels of verification are conducted: first, a classic benchmark dam break case is employed to confirm the feasibility of the hydrodynamic and breach evolution algorithms; second, published flume experimental data of non-cohesive earth dam overtopping failures are adopted to evaluate the model accuracy in predicting breach hydrographs and spatiotemporal evolution of breach geometry. The results demonstrate that the proposed model accurately reproduces the key characteristics of overtopping failure with high fidelity. The predicted breach flow rates and flow depths are in excellent agreement with experimental observations, with relative errors less than 5% for both peak discharge and time to peak. Consequently, this study provides a reliable numerical tool for detailed simulation of non-cohesive earth dam breaches and offers scientific support for emergency management. Full article

Entrained gas in hydraulic oil undermines system stability. A rapid engineering method for predicting the separation efficiency of gas–liquid cyclone separators is still lacking. This study proposes an engineering-oriented predictive framework by combining the split ratio, the characteristic scale of the locus of zero vertical velocity envelope, and the axial residence time. A relative migration index, derived from maximum tangential velocity and axial residence time, is coupled with a relative overflow-pipe insertion indicator to characterize the interaction between swirl intensity and effective separation space. The separation-capability transition is described using a coupled logistic mapping. Model coefficients are identified via Eulerian–Eulerian simulations on a calibration set. The model was evaluated on isolated simulation validation sets with varying geometries and inlet gas volume fractions, yielding an R² of 0.762 and a root mean square error (RMSE) of 0.07. Particle Image Velocimetry validation tests on one representative prototype geometry gave RMSE values of 0.061 for simulation versus test and 0.108 for prediction versus test. The framework captures the macroscopic trend of separation efficiency within the investigated range, with the caveat that part of the model coefficients and intermediate inputs remain conditioned by simulation-derived quantities. Full article

Hydrocyclones are widely applied devices in mineral processing due to their simple design, high capacity and low operational costs. Some of the main applications are classification in closed grinding circuits and desliming, as well as dewatering. However, hydrocyclones have an inherent inefficiency known as the fine particles bypass to the underflow stream, often associated with entrainment by water flow. Several approaches have been proposed to mitigate fine particle bypass, such as optimizing hydrocyclone design, adjusting apex and vortex finder diameters, water injection systems and improved inlet design. The objective of the present work was to assess hydrocyclone performance on different apex and vortex diameter combinations, seeking the reduction in fine particles bypass to underflow on the Paragominas bauxite processing industrial desliming circuit. Two different bauxite samples were used in a hydrocyclone classification test work, carried out on a specially built pilot plant. Six different combinations of apex and vortex were evaluated in a 254 mm diameter hydrocyclone, covering a range of apex-to-vortex diameters from 0.38 to 0.57. The results indicate operating conditions that significantly reduce fine particles bypass to underflow, increasing classification efficiency with minor effects in overflow selected size distribution parameter—d₉₅. Accordingly, smaller apex-to-vortex ratios result in overall better performances, reducing fine particles bypass to underflow from 33% to 7%, as well as reducing the partition curve slope from 0.52 to 0.21 for one of the tested samples. Significant benefits are also obtained in terms of reducing the contents of reactive silica in the underflow of the optimized desliming hydrocyclone. Full article

Circadian rhythms are predictable biological patterns that recur about every 24 h and, in mammals such as humans, are entrained to daylight by the hypothalamic suprachiasmatic nucleus (SCN). Although light is a potent zeitgeber for the SCN, cells outside of the SCN can synchronize to daily nutrient and metabolic cues. In these tissues, nutrient metabolic processes are regulated by the molecular clock in anticipation of food availability or scarcity. Furthermore, nutrients and metabolic processes themselves may act upon members of the molecular clock to regulate their expression and activity. These interactions maintain synchrony between the SCN and food-entrainable clocks when activity and nutrient intake align. However, the light-entrainable SCN and food-entrainable clocks can become desynchronized, particularly in modern society where humans are commonly exposed to shift work and jet lag. Therefore, the mechanisms for sensing nutrients at specific times of day are critical components of circadian timekeeping and organismal homeostasis. In the following narrative review, we aim to synthesize current evidence on time-of-day-dependent nutrient sensing in mammalian systems, examine how nutrient-derived signals and metabolic processes interact with molecular clock mechanisms across cellular and tissue levels, and evaluate the integration of central and peripheral clocks in regulating gene expression, energy utilization, and organismal homeostasis, including the impacts of feeding cycles and circadian disruption. While previous reviews have discussed circadian nutrient metabolism, this review provides conceptual support for the role of nutrients as time-of-day signaling mechanisms. Full article

This paper investigates the combustion dynamics of interacting lazy multi-component gas plumes (i.e., buoyancy-dominated gas releases with a low initial momentum flux), a configuration relevant to coal mining waste emissions. By coupling a three-dimensional large eddy simulation (mesh size of 10⁻² m; paralleling with 2048 processors) with detailed chemical kinetics (GRI-Mech 3.0), we analyzed the sensitivity of the flow structure and plume stabilization to the vent spacing of twin hydrogen-rich multi-component gas plumes (H₂-CO-CH₄-air). The results identified a distinct topological transition. While gas plumes from vents spaced at $\delta /D=5$ ($\delta$ and D are the spacing and width of gas vents, respectively) evolve independently, those at closely spaced sources ($\delta /D=5/4$) exhibit rapid coalescence driven by hydrodynamic shielding. This hydrodynamic merging results in a unified column with an effective hydraulic diameter of $D_{eff}\approx \sqrt{2}D$. This leads to a significant reduction in the surface-to-volume ratio available for ambient air entrainment, maintaining a coherent combustible-rich core to higher altitudes than isolated-source correlations would predict. However, despite this mass retention, the rapid vertical acceleration of buoyancy-dominated flows induces high strain rates, significantly disrupting the reaction zone structure. These findings establish that, for clustered emission sources, the dispersion hazard is governed by a coupling between hydrodynamic coalescence, which maintains reactant concentration, and finite-rate chemistry, restricting oxidation efficiency. This paper provides critical insights for designing gas capture infrastructure and assessing flammability limits in multi-vent systems. Full article