Search Results (419)

In China, weir-gully-type debris flows pose severe threats to transportation infrastructure, yet existing studies lack systematic analysis of their dynamic processes and early-warning strategies. This study innovatively integrates depth-integral modeling and field monitoring to investigate two unstable weirs upstream of the Zangyinggou Tunnel on the G30 Saiguo Expressway. The main research conclusions are as follows: (1) the influence of terrain and water source conditions on the weir-valley debris flow plays a dominant role; (2) the debris flows triggered by Weir I and II collapses reach the G30 Saiguo Expressway at 3560 s and 4000 s, respectively, with peak destructive capacities (cross-sectional sweep areas of 10.26 m²/s and 11.69 m²/s); (3) a three-level early-warning strategy was proposed, mainly based on water-level gauge monitoring and early warning, supplemented by video surveillance and regular measurement by small unmanned aerial vehicles. This study has established a brand-new idea for the monitoring and early warning of debris flow disasters induced by the collapse of barrier lakes along the G30 km line in Xinjiang. These achievements provide feasible insights for disaster reduction in mountainous transportation corridors, thus having significant practical value for promoting the sustainable development of infrastructure under the United Nations Sustainable Development Goals (SDGs). Full article

Cyanobacterial blooms in urban rivers present critical ecological threats worldwide, yet their mechanisms in fluvial systems remain inadequately explored compared to lacustrine environments. This study addresses this gap by investigating bloom dynamics in the eutrophic Majiagou River (Harbin, China) through phytoplankton resource use efficiency (RUE), calculated as chlorophyll-a per unit TN/TP. Seasonal sampling (2022–2024) across 25 rural-to-urban sites revealed distinct spatiotemporal patterns: urban sections exhibited 1.9× higher cyanobacterial relative abundance (RAC, peaking at 40.65% in autumn) but 28–30% lower RUE than rural areas. Generalized additive models identified nonlinear RAC–RUE relationships with critical thresholds: in rural sections, RAC peaked at TN-RUE 40–45 and TP-RUE 25–30, whereas urban sections showed lower TN-RUE triggers (20–25) and suppressed dominance above TP-RUE 10. Seasonal extremes drove RUE maxima in summer and minima during freezing/thawing periods. These findings demonstrate that hydrological stagnation (e.g., river mouths) and pulsed nutrient inputs reduce nutrient conversion efficiency while lowering bloom-triggering thresholds under urban eutrophication. The study establishes RUE as a predictive indicator for bloom risk, advocating optimized N/P ratios coupled with flow restoration rather than mere nutrient reduction. This approach provides a science-based framework for sustainable management of urban river ecosystems facing climate and anthropogenic pressures. Full article

A three-dimensional numerical simulation of hot air anti-icing was conducted on the full-annular realistic model of engine intake components, comprising the intake ducts, intake casing, struts, axial flow casing, and zero-stage guide vanes, based on the intermittent maximum icing conditions and the actual engine operating parameters. The simulation integrated multi-physics modules, including air-supercooled water droplet two-phase flow around components, water film flow and heat transfer on anti-icing surfaces, solid heat conduction within structural components, hot air flow dynamics in anti-icing cavities, and their coupled heat transfer interactions. Simulation results indicate that water droplet impingement primarily localizes at the leading edge roots and pressure surfaces of struts, as well as the leading edges and pressure surfaces of guide vanes. The peak water droplet collection coefficient reaches 4.2 at the guide vane leading edge. Except for the outlet end wall of the axial flow casing, all anti-icing surfaces of intake components maintain temperatures above the freezing point, demonstrating effective anti-icing performance. The anti-icing characteristics of the intake components are governed by two critical factors: cumulative heat loss along the hot air flow path and heat load consumption for heating and evaporating impinging water droplets. The former induces a 53.9 °C temperature disparity between the first and last struts in the heating sequence. For zero-stage guide vanes, the latter factor exerts a more pronounced influence. Notable temperature reductions occur on the trailing edges of three struts downstream of the hot air flow and at the roots of zero-stage guide vanes. Full article

This study investigates the leakage vortex influence on pressure pulsation characteristics within a vertical axial flow pump. Three impeller configurations with blade root clearance (δ) of 2.7–8.0 mm were designed to analyze geometric effects on internal flow dynamics. Unsteady RANS simulations predicted flow structures under multiple operating conditions (0.8–1.2Q_des). Fast Fourier Transform (FFT) extracted frequency–domain and time–frequency characteristics of pressure pulsations in critical flow regions. Key results reveal: (1) δ enlargement expands low-pressure zones within blade channels due to enhanced leakage vortices; (2) leading-edge pulsation shows 8.2–11.7% reduction in peak-to-peak amplitude and fundamental frequency magnitude with increasing δ; (3) trailing-edge response exhibits non-monotonic behavior, with maximum amplitude at δ = 5.0 mm (42.2% increase at design flow). These findings demonstrate that blade root clearance optimization requires condition-dependent thresholds to balance leakage management and pulsation control. Full article

Indirect evaporative coolers (IECs) are becoming a viable alternative to the more energy-intensive traditional HVAC systems for space cooling, especially in arid regions. In this work, a recently developed computational model of an IEC was used to conduct a parametric study. The model employs a spray dryer model to track the flow path and evaporation rate of droplets. The key parameters investigated were the temperature of the droplets, a bypass effect where the amount of exhaust air and water was reduced to as low as 10%, and the length of the heat exchanger. The results suggest that the wet bulb efficiency could be increased from the previously observed 35% to 72.5% if the water temperature is decreased to 16 °C. In order to drastically increase the performance, the heat exchanger length should be increased from 50 cm to 100 cm, which could still end up in a more compact design overall as fewer plates are required. The bypass study resulted in peak performance when 40% of the secondary air flow was used as working air in conjunction with a proportional reduction in water usage. Overall, the computational model has been employed in an attempt to reduce the bulkiness, increase the efficiency and reduce the water consumption of such a system. Full article

This study investigated the freeze–thaw resistance of ordinary and nano-TiO₂-modified concrete (NTC) based on mass loss, ultrasonic velocity, compressive strength, and fracture toughness. The compressive behavior and internal damage evolution were further analyzed using particle flow code in two dimensions (PFC^2D) simulations. The results show that, although neither material exhibited structural collapse after freeze–thaw cycling, visible surface damage was observed, particularly in ordinary concrete. After 100 cycles, NTC showed a 52.17% reduction in mass loss and a 37.31% increase in ultrasonic velocity compared to ordinary concrete. Compressive strength of ordinary concrete decreased by 24.28 MPa (from 41.53 MPa to 17.25 MPa), while that of NTC decreased by only 13.37 MPa, demonstrating that the incorporation of nano-TiO₂ effectively improves the compressive performance of concrete under freeze–thaw conditions. Fracture toughness after 100 cycles decreased by 89.7% in ordinary concrete and 80.9% in NTC, suggesting that while nano-TiO₂ mitigates damage, its effect on maintaining fracture load-carrying capacity remains limited. The PFC^2D simulations were consistent with the experimental results, effectively capturing peak compressive behavior and validating the model’s applicability for freeze–thaw degradation analysis. Full article

This study presents a comprehensive analysis of hydration heat-induced temperature and stress fields in a U-shaped aqueduct during the casting phase, integrating field measurements and numerical simulations. The key findings are as follows: (1) Thermal Evolution Characteristics: Both experimental and numerical results demonstrated consistent thermal behavior, characterized by a rapid temperature rise, subsequent rapid cooling, and eventual stabilization near ambient conditions. The peak temperature is observed at the centroid of the bearing section’s base slab, reaching 83.8 °C in field tests and 87.0 °C in simulations. (2) Stress Field Analysis: Numerical modeling reveals critical stress conditions in the outer concrete layers within high-temperature zones. The maximum tensile stress reaches 6.37 MPa, exceeding the allowable value of the tensile strength of the current concrete (1.85 MPa) by 244%, indicating a significant risk of thermal cracking. (3) Temperature Gradient and Cooling Rate Anomalies: Both methodologies identify non-compliance with critical control criteria. Internal-to-surface temperature differentials exceed the 25 °C threshold. Daily cooling rates at monitored locations surpass 2.0 °C/d during the initial 5–6 days of the cooling phase, elevating cracking risks associated with excessive thermal gradients. (4) Mitigation Strategy Proposal: Implementation of a hydration heat control system is recommended; compared to single-layer systems, the proposed mid-depth double-layer steel pipe cooling system (1.2 m/s flow) reduced peak temperature by 23.8 °C and improved cooling efficiency by 28.7%. The optimized water circulation maintained thermal balance between concrete and cooling water, achieving water savings and cost reduction while ensuring structural quality. (5) The cooling system proposed in this paper has certain limitations in terms of applicable environment and construction difficulty. Future research can combine with a BIM system to dynamically control the tube cooling system in real time. Full article

To address compacted soils with high power consumption and waterlogging risks in rice–rapeseed rotation areas of the Yangtze River, this study designed a ditching machine combining a stepped cutter head and trapezoidal cleaning blade, where the mechanical synergy between components minimizes energy loss during soil-cutting and -throwing processes. We mathematically modeled soil cutting–throwing dynamics and blade traction forces, integrating soil rheological properties to refine parameter interactions. Discrete Element Method (DEM) simulations and single-factor experiments analyzed impacts of the inner/outer blade widths, blade group distance, and blade opening on power consumption. Results indicated that increasing the inner/outer blade widths (200–300 mm) by expanding the direct cutting area significantly reduced the cutter torque by 32% and traction resistance by 48.6% from reduced soil-blockage drag; larger blade group distance (0–300 mm) initially decreased but later increased power consumption due to soil backflow interference, with peak efficiency at 200 mm spacing; the optimal blade opening (586 mm) minimized the soil accumulation-induced power loss, validated by DEM trajectory analysis showing continuous soil flow. Box–Behnken experiments and genetic algorithm optimization determined the optimal parameters: inner blade width: 200 mm; outer blade width: 300 mm; blade group distance: 200 mm; and blade opening: 586 mm, yielding a simulated power consumption of 27.07 kW. Field tests under typical 18.7% soil moisture conditions confirmed a <10% error between simulated and actual power consumption (28.73 kW), with a 17.3 ± 0.5% reduction versus controls. Stability coefficients for the ditch depth, top/bottom widths exceeded 90%, and the backfill rate was 4.5 ± 0.3%, ensuring effective drainage for rapeseed cultivation. This provides practical theoretical and technical support for efficient ditching equipment in rice–rapeseed rotations, enabling resource-saving design for clay loam soils. Full article

The construction industry is responsible for 39% of global CO₂ emissions related to energy use, with cement responsible for 5–8% of it. Limestone calcined clay cement (LC³), a ternary blended binder system, offers a low-carbon alternative by partially substituting clinker with calcined clay and limestone. This study investigated the use of waste clay brick powder (WBP), a waste material, as a source of calcined clay in LC³ formulations, addressing both environmental concerns and SCM scarcity. Two LC³ mixtures containing 15% limestone, 5% gypsum, and either 15% or 30% WBP, corresponding to clinker contents of 65% (LC³-65) or 50% (LC³-50), were evaluated against general purpose (GP) cement mortar. Tests included setting time, flowability, soundness, compressive and flexural strengths, drying shrinkage, isothermal calorimetry, and scanning electron microscopy (SEM). Isothermal calorimetry showed peak heat flow reductions of 26% and 49% for LC³-65 and LC³-50, respectively, indicating a slower reactivity of LC³. The initial and final setting times of the LC³ mixtures were 10–30 min and 30–60 min longer, respectively, due to the slower hydration kinetics caused by the reduced clinker content. Flowability increased in LC³-50, which is attributed to the lower clinker content and higher water availability. At 7 days, LC³-65 retained 98% of the control’s compressive strength, while LC³-50 showed a 47% reduction. At 28 days, the compressive strengths of mixtures LC³-65 and LC³-50 were 7% and 46% lower than the control, with flexural strength reductions being 8% and 40%, respectively. The porosity calculated from the SEM images was found to be 7%, 11%, and 15% in the control, LC³-65, and LC³-50, respectively. Thus, the reduction in strength is attributed to the slower reaction rate and increased porosity associated with the reduced clinker content in LC³ mixtures. However, the results indicate that the performance of LC³-65 was close to that of the control mix, supporting the viability of WBP as a low-carbon partial replacement of clinker in LC³. Full article

Objectives: This study evaluates the efficacy of existing and new aerosol mitigation methods during nebulization (Neb) in combination with high-flow nasal cannula (HFNC) oxygen supplementation and non-invasive ventilation (NIV). Methods: We recorded fugitive aerosol particle concentrations over time and assessed the peak (P) and area (A) efficacy of active and passive mitigation methods, comparing them to a no-mitigation condition. Peak efficacy was measured by the reduction in maximum aerosol concentration, while area efficacy was quantified by the reduction of the area under the aerosol concentration–time curve. Results: For HFNC with Neb, we found that active mitigation using a mask with a biofilter and a fan (referred to as the aerosol barrier mask) significantly outperformed passive mitigation with a face mask. The peak and area efficacy for aerosol reduction were 99.0% and 96.4% for active mitigation and 35.9% and 7.6% for passive mitigation, respectively. For NIV with Neb, the active mitigation method, using a box with a biofilter and fan, also outperformed passive mitigation using only the box. The peak and area efficacy for aerosol reduction were 92.1% and 85.5% for active mitigation and 53.7.0% and 25.4% for passive mitigation, respectively. Conclusion: We concluded that active mitigation set up systems advantageous for effective reduction of airborne aerosols during aerosol generated procedures. Full article

Rainfall infiltration is a key factor affecting the stability of the slope. To study the impact of rainfall on the instability mechanism and stability of slopes, this paper employs numerical simulation to establish a rainfall infiltration slope model and conducts a saturated–unsaturated slope flow and solid coupling numerical analysis. By combining the strength reduction method with the calculation of slope stability under rainfall infiltration, the safety factor of the slope is obtained. A comprehensive analysis is conducted from the perspectives of the seepage field, displacement field and other factors to examine the impact of heavy rainfall patterns and rainfall intensities on the instability mechanism and stability of the slope. The results indicate that heavy rainfall causes the transient saturation zone within the landslide body to continuously move upward, forming a continuous sliding surface inside the slope, which may lead to instability and sliding of the soil in the upper part of the slope toe. The heavy rainfall patterns significantly affect the temporal and spatial evolution of pore water pressure, displacement and safety factors of the slope. Pore water pressure and displacement show a positive correlation with the rainfall intensity at various times during heavy rainfall events. The pre-peak rainfall pattern causes the largest decrease in the safety factor of the slope, and the slope failure occurs earlier, which is the most detrimental to the stability of the slope. The rainfall intensity is inversely proportional to the safety factor. As the rainfall intensity increases, the decrease in the slope’s safety factor becomes more significant, and the time required for slope instability is also shortened. The results of this study provide a scientific basis for analyzing rainfall-induced slope instability and failure. Full article

A concentric double-flange butterfly valve (DN-500, PN-10) was analyzed to examine its dynamic behavior and internal fluid flow across multiple opening angles. Finite Element Analysis (FEA) was employed to determine natural frequencies, mode shapes, and effective mass participation factors (EMPFs) for valve positions at 30°, 60°, and 90°. The valve geometry was discretized using a curvature-based mesh with linear elastic isotropic properties for 1023 carbon steel. Lower-order vibration modes produced global deformations primarily along the valve disk, while higher-order modes showed localized displacement near the shaft–bearing interface, indicating coupled torsional and translational dynamics. The highest EMPF in the X-direction occurred at 1153.1 Hz with 0.2631 kg, while the Y-direction showed moderate contributions peaking at 0.1239 kg at 392.06 Hz. The Z-direction demonstrated lower influence, with a maximum EMPF of 0.1218 kg. Modes 3 and 4 were critical for potential resonance zones due to significant mass contributions and directional sensitivity. Computational Fluid Dynamics (CFD) simulation analyzed flow behavior, pressure drops, and turbulence under varying valve openings. At a lower opening angle, significant flow separation, recirculation zones, and high turbulence were observed. At 90°, the flow became more streamlined, resulting in a reduction in pressure losses and stabilizing velocity profiles. Full article

As the largest freshwater lake in China, Poyang Lake plays a crucial role in hydrological processes. Conventional models often fail to capture the time-lagged relationships between meteorological drivers and runoff responses, while lacking regional generalization capability. To address these limitations, this study proposes a novel XAJ-LSTM-TFM hybrid model that accounts for time-lagged hydrological responses and enhances the regional applicability of the Xinanjiang model. The model innovatively integrates the physical mechanisms of the Xinanjiang model with the temporal learning capacity of LSTM networks. By incorporating intermediate hydrological variables (including interflow and groundwater flow) along with 1–3 day lagged meteorological features, the model achieves an average 15.3% improvement in Nash–Sutcliffe Efficiency (NSE) across five sub-basins, with the Ganjiang Basin attaining an NSE of 0.812 and a 25.7% reduction in flood peak errors. The results demonstrate superior runoff simulation performance and reliable generalization capability under intensive anthropogenic activities. Full article

Improving photovoltaic (PV) panel performance under extreme climatic conditions is critical for advancing sustainable energy systems. In hyper-arid regions, elevated operating temperatures significantly reduce panel efficiency. This study investigates and compares three cooling techniques—air cooling, water cooling, and porous media cooling—using thermal and electrical modeling based on CFD simulations in ANSYS. The numerical model replicates a PV system operating under peak solar irradiance (900 W/m²) and realistic ambient conditions in Adrar, Algeria. Simulation results show that air cooling leads to a modest temperature reduction of 6 °C and a marginal efficiency gain of 0.25%. Water cooling, employing a top-down laminar flow, reduces cell temperature by over 35 °C and improves net electrical output by 30.9%, despite pump energy consumption. Porous media cooling, leveraging passive evaporation through gravel, decreases panel temperature by around 30 °C and achieves a net output gain of 26.3%. Mesh sensitivity and validation against experimental data support the accuracy of the model. These findings highlight the significant potential of water and porous material cooling strategies to enhance PV performance in hyper-arid environments. The study also demonstrates that porous media can deliver high thermal effectiveness with minimal energy input, making it a suitable low-cost option for off-grid applications. Future work will integrate long-term climate data, real diffuser geometries, and experimental validation to further refine these models. Full article

Contemporary evaluation and surgical approaches in congenital aortic valve disease have yielded limited success. The ability to evaluate and understand detailed flow characteristics surrounding surgical repair may be beneficial. This study explores the feasibility and utility of echocardiographic-based blood speckle imaging (BSI) in assessing pre- and post-operative flow characteristics in those with non-stenotic congenital aortic root disease undergoing aortic valve repair or valve-sparing root replacement (VSRR) surgery. Transesophageal echocardiogram was performed during the pre-operative and post-operative assessment surrounding aortic surgery for ten patients with non-stenotic congenital aortic root disease. BSI, utilizing block-matching algorithms, enabled detailed visualization and quantification of flow parameters from the echocardiographic data. Post-operative BSI unveiled enhanced hemodynamic patterns, characterized by quantified changes suggestive of the absence of stenosis and no more than trivial regurgitation. Rectification of an asymmetric jet and the reversal of flow on the posterior aspect of the ascending aorta resulted in a reduced oscillatory shear index ($OSI$) of $0.0543\pm 0.0207$ (pre-op) vs. $0.0275\pm 0.0159$ (post-op) and $p=0.0044$, increased peak wall shear stress of $1.9423\pm 0.6974$ (pre-op) vs. $3.6956\pm 1.4934$ (post-op) and $p=0.0035$, and increased time-averaged wall shear stress of $0.6885\pm 0.8004$ (pre-op) vs. $0.8312\pm 0.303$ (post-op) and $p=0.23$. This correction potentially attenuates cellular alterations within the endothelium. This study demonstrates that children and young adults with non-stenotic congenital aortic root disease undergoing valve-preserving operations experience significant improvements in flow dynamics within the left ventricular outflow tract and aortic root, accompanied by a reduction in $OSI$. These hemodynamic enhancements extend beyond the conventional echocardiographic assessments, offering immediate and valuable insights into the efficacy of surgical interventions. Full article