Search Results (3,610)

Hydraulic fracturing is a key technology for the commercial exploitation of deep shale gas reservoirs, and accurate prediction of rock-mechanical parameters is essential for optimizing these operations. Conventional approaches primarily rely on empirical formulas based on longitudinal and transverse wave velocities; however, obtaining transverse wave data is challenging, and these formulas often lack accuracy. Conventional machine learning algorithms also exhibit limited predictive performance and generalization due to the intrinsic heterogeneity of rock-mechanical data. Therefore, to address the extreme heterogeneity and complex nonlinear logging responses inherent in deep shale gas reservoirs in the Zigong (ZG) block, this study proposes a geology-tailored deep learning framework, CNN-BiGRU-AT. Unlike generic machine learning applications, this architecture is specifically designed to decode complex stratigraphic signals: the convolutional neural network (CNN) module extracts multi-scale spatial features to capture abrupt lithological transitions; the bidirectional gated recurrent units (BiGRUs) analyzes the continuous depth-sequential dependencies of overlying and underlying strata; and the attention mechanism (AT) dynamically regulates the weight allocation of critical input geophysical parameters, thereby delivering a geophysically informative and highly robust predictive performance. This paper employs the CNN-BiGRU-AT model to predict the Brittleness index (BI), using the ZG block as an example. The results demonstrate that the coefficient of determination (R²) for the brittleness index on the test dataset achieved 0.969, representing a 12% improvement over conventional models. The high accuracy of this model satisfies the precision requirements for predicting rock-mechanical parameters, thereby offering reliable theoretical support for optimizing hydraulic fracturing operations in deep shale gas reservoirs. Full article

This study proposes two enhanced configurations for a parallel-channel cold plate in battery thermal management systems to improve thermo-hydraulic performance through the introduction of cylindrical and fin-type baffles. A three-dimensional computational fluid dynamics (CFD) model was developed in ANSYS to simulate fluid flow and heat transfer within the cold plate. A Poly-Hexcore meshing strategy with local refinement and near-wall inflation layers was employed to ensure numerical accuracy while maintaining computational efficiency. A parametric investigation involving 150 cases was conducted to identify the optimal channel configuration. The results indicate that, among the investigated configurations and under the present numerical operating conditions, the fin-type baffle exhibits the most balanced thermo-hydraulic behavior by achieving an effective balance between heat-transfer enhancement and pressure-drop penalty. The present study provides a CFD-based framework for the design and optimization of parallel-channel cold plates for battery thermal management applications. Full article

This study systematically investigated flow boiling characteristics within a novel three-layer microchannel heat sink with 3/4 open-ring pin fin arrays, designed for high-heat-flux thermal management of low-carbon metallurgical reactors. Two-phase flow regimes, pressure drop, and wall temperature responses were analyzed. To evaluate the impact of functional surface material properties on thermo-hydraulic behavior, a hydrophilic nano-coating modification was applied to the inner copper channel walls for comparison. Increasing the flow rate triggered a transition from a vapor-dominated confined slug flow to a liquid-dominated dispersed bubble flow, which effectively improved the thermo-hydraulic stability. Hydrophilic surface modification resulted in an average pressure drop reduction of 33% and significantly diminished the sensitivity of flow resistance to velocity variations. Through hydrophilic treatment, the localized vapor film effect at high velocities was suppressed, and temperature field homogenization was promoted, yielding a maximum convective heat transfer coefficient of 7760 W/(m²·°C), i.e., 72.9% enhancement over the baseline heat sink. The underlying mechanism is attributed to the formation of a stable near-wall thin liquid film and the promotion of high-frequency nucleate boiling. These results will be of high relevance for developing efficient cooling solutions for power electronics, thereby supporting the advancement of low-carbon metallurgical reactors. Full article

This study presents a controlled three-dimensional conjugate CFD comparison of counter-flow and parallel-flow concentric tube heat exchangers under identical Reynolds number conditions (Re = 1000–2000). By isolating the flow configuration as the only varying parameter, the intrinsic influence of flow arrangement on thermo-hydraulic performance is systematically evaluated. Unlike enhancement-focused studies involving geometric modification or advanced working fluids, the present study focuses exclusively on the influence of flow arrangement under identical operating conditions. The analysis focuses on heat transfer rate, outlet temperature distribution, pressure drop, thermo-hydraulic performance index, and a normalized heat transfer ratio (Ψ). The results show that the counter-flow configuration consistently enhances heat transfer by 3.17–4.29% compared to parallel-flow operation, while maintaining nearly identical pressure-drop values. This improvement is attributed to the preservation of a higher logarithmic mean temperature difference (LMTD) along the exchanger length, sustaining the thermal driving force under laminar flow conditions. In contrast, the parallel-flow configuration exhibits a rapid decay in temperature difference near the inlet region, limiting effective heat transfer. Although heat transfer increases with Reynolds number in both configurations, the thermo-hydraulic performance index decreases due to the relatively higher increase in hydraulic resistance. Comparison with classical laminar flow behavior confirmed the physical consistency and reliability of the numerical model. The findings demonstrate that counter-flow arrangement provides a measurable thermal advantage without additional hydraulic penalty. The study offers a physically consistent and practically relevant framework for the design and optimization of concentric tube heat exchangers used in engine cooling and waste heat recovery applications. Full article

Urban stormwater is often viewed as a drainage problem rather than a local water resource, even in areas where runoff capture could simultaneously reduce flooding and promote the reuse of non-potable water. This study develops, installs, and field-tests a decentralized, school-scale stormwater harvesting system that relocates permeable concrete, transforming it from a passive infiltration surface into a purpose-built capture and pretreatment interface. The system integrates a 3 m × 3 m permeable concrete slab with load-bearing sections, an impermeable underlayer to ensure controlled flow, a double-compartment sump for staged sedimentation and hydraulic damping, sequential filtration with sand/gravel and activated carbon, and a 5000 L storage tank. The prototype was implemented at CETis 105 in Querétaro, Mexico, and evaluated during its commissioning and operation in the 2023 rainy season. Field operations demonstrated reduced ponding in the catchment area and a reliable flow of runoff to the pretreatment units. In the sump compartments, apparent color decreased from 221 to 59 Pt-Co, turbidity from 46.8 to 12.9 NTU, and COD from approximately 30–35 to 15–18 mg·L⁻¹, corresponding to approximate pretreatment reductions of 73.3%, 72.4%, and 40–57%, respectively, before post-filtration. Conversely, the elevated pH, electrical conductivity, and total dissolved solids indicated interaction with fresh cementitious materials and dissolved ionic residues during initial operation, highlighting the need for curing, initial washing, and post-filtration verification before declaring compliance with reuse requirements. Therefore, the results support the feasibility of the proposed configuration as a decentralized, low-infrastructure architecture for localized runoff control and pretreatment, while confirming that full reuse validation still requires microbiological and post-filtration evaluation. The study provides a field-proven system design adaptable to school campuses and similar institutional environments for distributed stormwater management and non-potable water storage. Full article

As extreme-scale manufacturing evolves, the dynamic response of heavy moving components under ultra-high loads becomes a critical design challenge. This study focuses on friction-induced vibration of a more than 30-ton movable mass during the mold-opening stage in a two-platen machine with a clamping force >17,000 kN. A mathematical model and a validated rigid/flexible multibody dynamics model with PID co-simulation were developed to analyze transient vibration using maximum acceleration amplitude and stability time as core metrics. The results show vibration stems from imbalance between anti-opening resistance and hydraulic driving force, amplified by vacuum collapse, static-to-dynamic friction transition at slide feet/rail interface and PID overshoot, featuring high amplitude density (>0.75 g), transience (<50 ms) and high impact (>60,000 N). The maximum vibration acceleration amplitude remains 79.22% even after there is no mold vacuum suction, indicating that a static friction force other than the vacuum suction is the dominant factor resulting in a severe friction-induced vibration. These mechanistic insights establish an applicable framework for the dynamic optimization of the heavy components in extreme-large-scale manufacturing equipment. Full article

A design for a small chloride salt fast reactor (sm-MCFR) is presented through the integration of molten salt reactor and small reactor technologies, targeting efficient transmutation of transuranic (TRU) elements in spent nuclear fuel and rapid reactor deployment. The feasibility exploration and research on the design boundaries of sm-MCFR will be conducted in this article. The core adopts a dual-fluid configuration, in which the fuel salt and coolant circulate independently. Chloride salt is selected as the fuel carrier due to its high solubility for heavy metal nuclides and the low neutron absorption cross-section of chlorine, which help to form a hard fast-neutron spectrum and thereby enhance transmutation efficiency. The cooling system employs a direct supercritical carbon dioxide (s-CO₂) cycle, simplifying the overall layout. For the neutronics design, simulations were carried out using the TMCBurnup (TRITON MODEC Coupled Burnup Code). By adjusting the core geometry, fuel salt composition, and reprocessing strategy, the sm-MCFR achieves a hard fast-neutron spectrum but also demonstrates good potential for fuel utilization. In terms of thermal–hydraulic design, the heat exchange effect of the reactor core can be improved by adjusting the proportion of the coolant and the flow direction. The sm-MCFR is expected to become a promising candidate for advanced small reactors that have potential applications in nuclear waste transmutation and distributed energy generation. Full article

To alleviate the eutrophication in the Wuliangsuhai watershed and evaluate the pollutant reduction performance of ecological drainage ditches in the Hetao Irrigation District, a controlled field simulation experiment was conducted using synthetic agricultural return-flow water formulated from long-term monitoring data. Three leguminous plant treatments, two microbial substrate treatments, and one control were established to compare the migration and transformation of total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD) in overlying water, sediment, and plants under different hydraulic retention time intervals (0–6 h, 6–12 h, and 12–18 h). The results showed that plant treatments generally improved conventional water quality indicators, with increased pH and dissolved oxygen (DO) and decreased electrical conductivity, salinity, and total dissolved solids, whereas microbial substrate treatments tended to reduce DO. Pollutant reduction performance differed among treatments. Medicago sativa showed the strongest TN removal from overlying water, Microbial biological rope exhibited the best TP removal from overlying water, and Melilotus suaveolens performed best in COD reduction. Among all plant treatments, Astragalus laxmannii exhibited the most stable overall performance and a relatively strong integrated capacity for nitrogen and phosphorus retention. Most TN and TP reduction in overlying water and sediment occurred during the initial hydraulic retention time interval of 0–6 h, whereas TN plant uptake became more evident during 12–18 h. These findings suggest that ecological drainage ditches vegetated with locally adapted leguminous species have potential to mitigate agricultural non-point source pollution in arid irrigation districts. In particular, Astragalus laxmannii appears to be a promising candidate for ecological ditch design in the Hetao Irrigation District. However, this study was conducted under controlled synthetic return-flow conditions rather than with actual field drainage water, and no tracer-based hydrodynamic verification was performed; therefore, the reported hydraulic retention time effects and treatment efficiencies should be interpreted cautiously. Further field-scale validations under real drainage, seasonal variation, and long-term operation conditions are still needed. Full article

To mitigate the risks of pressure surges and water hammer during accidental pump trips in industrial cooling water systems, accurate boundary modeling of cooling towers is essential. This study employs the Method of Characteristics (MOC) to evaluate four equivalent models for the central riser shaft: Model A (constant level), Model B (two-way surge tank), Model C (dynamic coupling of shaft and distribution channel), and Model D (composite structure). Results indicate that Model A fails to reflect actual hydraulic states, producing an unrealistic pump reverse speed of −253.24 r/min and overly conservative estimates. While Models B, C, and D exhibit similar pressure trends, Model C most accurately captures the physical drainage process, realistically simulating how the shaft level stabilizes at the distribution channel elevation before declining. By accurately reflecting engineering hydraulics, Model C provides the most reliable basis for water hammer safety assessments. It is recommended for optimizing pump valve closure strategies, vacuum breaker installations, and siphon protection designs in power plant systems. Full article

Unconventional oil and gas reservoirs naturally have low porosity and low permeability, which necessitate reservoir stimulation during production to achieve commercial exploitation. Therefore, to improve reservoir stimulation effectiveness, this study established a thermal–hydraulic–mechanical coupled numerical model suitable for hydraulic fracturing experiment scales based on rock mechanics, elasticity mechanics, damage mechanics, and flow mechanics theories, combined with maximum principal stress and Mohr–Coulomb damage criteria. The model was numerically solved within a finite element framework and used to simulate the reservoir hydraulic fracturing process. The results indicate that the propagation behavior of hydraulic fractures is controlled by reservoir rock mechanical properties, geostresses, reservoir temperatures, fracturing fluid viscosities, and injection rates. Among these, the increase in principal stress difference, reservoir temperature, fracturing fluid viscosity and injection rate promotes the propagation of hydraulic fractures along the direction of the maximum horizontal principal stress, whereas an increase in the rock’s elastic modulus reduces the propagation length of the hydraulic fractures. During fracturing, the fracturing fluid fractures the reservoir rock, significantly improving its porosity and permeability. This not only enhances the mobilization of unconventional oil and gas resources but also provides effective flow pathways for their migration, thereby ensuring the commercial viability of unconventional oil and gas resource extraction. Additionally, selecting a fracturing process that matches the geological characteristics of the study area during fracturing design is a prerequisite for improving the reservoir stimulation effect. The results of this study provide a reference for fracturing design and optimization. Full article

Electro-hydraulic servo systems are widely used in industrial machinery and automation due to their high power density and fast dynamic response; however, their achievable positioning accuracy is often limited by nonlinear friction effects. In many robust control strategies, including sliding mode control and its multi-surface variants, friction is commonly treated as a lumped bounded disturbance. This simplification neglects the dynamic and operating condition-dependent nature of friction, leaving the practical value of explicit friction compensation insufficiently clarified, especially for electro-hydraulic actuators operating near their bandwidth limits. This paper presents an experimental evaluation of LuGre-based dynamic friction compensation integrated into a multi-surface sliding mode control framework for electro-hydraulic actuators. Rather than proposing a new control methodology, the study focuses on clarifying, from a control-oriented mechanical engineering perspective, how friction compensation influences closed-loop tracking performance under different operating regimes. The proposed scheme is implemented on a laboratory-scale electro-hydraulic test bench and evaluated using step and sinusoidal reference motions over a wide range of excitation frequencies, from low-speed operation to the practical bandwidth limit of the actuator. Comparative experiments with a conventional proportional–integral–derivative controller and a multi-surface sliding mode controller without friction compensation are conducted to isolate the effect of explicit friction modeling. The experimental results reveal a strongly frequency-dependent influence of friction on tracking performance. At low excitation frequencies (e.g., 0.1 Hz), friction compensation provides only marginal improvement in root mean square (RMS) tracking errors. In contrast, as the excitation frequency approaches the actuator bandwidth limit (1 Hz), explicit LuGre-based friction compensation reduces the relative RMS tracking error by approximately 57% compared with the baseline MSSM controller and by up to 82% relative to a conventional PID controller. These results demonstrate that the effectiveness of friction compensation is highly dependent on operating conditions, providing experimentally grounded guidance for the design of control strategies for bandwidth-limited electro-hydraulic machines. Full article

This study develops a ternary Fe-based geopolymer system composed of metakaolin (MK), red mud (RM), and fly ash (FA) for the preparation of sustainable water-retaining subgrade materials for sponge-city roadbed applications. Unlike conventional formulations primarily designed for structural strength or rapid permeability, the proposed MK–FA–RM system was designed to improve water-storage capacity while maintaining adequate mechanical support and environmental compatibility. In this ternary system, MK provides highly reactive aluminosilicate species for geopolymer network formation, RM introduces Fe-bearing phases and enhances industrial solid-waste utilization, and FA contributes to particle packing, workability, and resource efficiency. A constrained ternary mixture design implemented using Design-Expert software was adopted to optimize precursor proportions. Within the investigated compositional range, the fitted first-order mixture model showed acceptable statistical adequacy for preliminary composition screening (R² = 0.86). The optimal blend (60% MK, 30% RM, and 10% FA) achieved a 7-day compressive strength of 8.37 MPa and a water retention rate of 35.3% under ambient curing conditions, satisfying the strength requirement considered for the target subgrade/base-layer application. Microstructural and phase analyses suggest that the synergistic interaction of the three precursors promoted Fe-modified aluminosilicate gel formation together with conventional geopolymer gel products, while improving matrix continuity and preserving interconnected pore space for water storage. This multiscale structural effect helps explain how the material achieved a balance between water retention capacity and mechanical support. Under the tested conditions, the material maintained acceptable residual strength after short-term exposure to water, acid, and sulfate-containing solutions. Life-cycle assessment indicated a 70% reduction in CO₂ emissions compared with ordinary Portland cement, while pilot-scale cost analysis showed a 39% lower production cost than MetaMax-based geopolymer materials. Pilot-scale application further demonstrated the constructability and water-regulation potential of the material in practical environments. Overall, the proposed ternary Fe-based geopolymer demonstrates that Fe-rich industrial wastes can be engineered into low-carbon and economically viable water-retaining subgrade materials that balance hydraulic regulation, structural adequacy, and sustainability. Nevertheless, long-term durability, cyclic loading performance, and direct nanoscale characterization of Fe-bearing gel evolution still require further investigation. Full article

Floods are among the most frequent and destructive natural hazards, causing significant socio-economic losses worldwide. This paper presents a comprehensive review of floodwall technologies, focusing on the integration of ultra-high-performance fibre-reinforced concrete (UHPFRC) to enhance structural and hydraulic performance. Flood protection systems are categorized into permanent, demountable, and temporary, and are evaluated based on parameters such as activation time, seepage resistance, and lifecycle cost. This review examines key structural applications, including floodwall barriers, wave-energy floaters, and retaining walls, in which UHPFRC provides significant advantages such as reduced material consumption, improved impact resistance, and increased durability in harsh environmental conditions. Additionally, recent advancements in floodwall systems are critically assessed through experimental investigations, numerical modelling, and hydraulic performance under varied loading and flow conditions. The analysis reveals that while UHPFRC systems can reduce material volumes by up to 73% and carbon emissions by 49% compared to conventional reinforced concrete, their adoption is currently limited by a lack of dedicated design standards. Based on a synthesis of peer-reviewed studies (2010–2026), findings indicate that autonomous, buoyancy-driven UHPFRC barriers offer the highest reliability in high-risk zones, whereas manual modular systems remain limited by human-factor vulnerabilities during rapid deployment. Critical research gaps are identified—specifically the need for standardized constitutive models for UHPFRC in hydrostatic environments and extensive long-term field validation—to support the transition toward resilient, smart urban flood defence infrastructure. Full article

Chinese Traditional Concrete (CTC), known as “San-he-tu,” has ensured the long-term durability of ancient coastal structures, yet its underlying material design logic remains insufficiently understood. This study investigates the Chongwu Ancient City Wall (Quanzhou, China), a Ming Dynasty granite fortification exposed to over 600 years of marine weathering, to elucidate the structure–property–function relationships of CTC across three functional layers: the horse-track surface, wall core backfill, and masonry bonding layer. A multi-technique analytical framework (XRF, XRD, TG, and SEM) was employed to characterize chemical composition, mineral phases, thermal behavior, and microstructure. Results reveal a deliberate “functional adaptability” material design. The surface layer adopts a rigid protective formulation with high quartz (76.9%) and CaO (17.06%), forming a dense, low-porosity matrix resistant to abrasion and weathering. The wall core exhibits a flexible filling strategy with high porosity (35.44%), enabling moisture dissipation and deformation accommodation. The bonding layer, enriched in kaolinite (~29.8%) and reactive Al–Fe components, promotes pozzolanic reactions that generate hydraulic gels, ensuring durable interfacial adhesion under humid coastal conditions. These findings demonstrate that ancient builders engineered zone-specific material compositions to meet distinct structural and environmental demands, forming a functionally graded system analogous to modern material design concepts. This study provides a scientific basis for adopting partitioned, differentiated restoration strategies in coastal heritage conservation. Full article

Solid–liquid transport pumps are widely used in slurry conveying, deep-sea mining, and sediment-laden water delivery, where suspended particles substantially modify internal flow behavior, energy transfer, and operational stability. This review systematically summarizes recent progress on flow evolution and stability issues in centrifugal pumps and related particle-laden pump systems. The fundamental mechanisms of particle dynamics are first discussed, including single-particle transport and force response, particle collision and agglomeration, turbulence modulation by particle assemblies, and wake-induced local disturbances. On this basis, the review further examines particle-induced changes in global flow topology, local separation and backflow, leakage shear layers, and the evolution of representative vortex structures, with particular attention to the enhancement of flow unsteadiness. In addition, the influences of particle size, concentration, density, and shape on hydraulic performance, wear failure, and operational reliability are summarized, together with recent advances in stability evaluation and fault diagnosis. Although substantial progress has been achieved, current studies still show limitations in cross-scale correlation, unified mechanism interpretation, and life-cycle coupled analysis. This review provides a useful reference for understanding solid–liquid two-phase flow mechanisms and for improving anti-wear design and stable operation control of transport pumps. Full article