Search Results (42)

The flow characteristics at the tributary entrance are crucial for ensuring safe navigation where the main channel and tributary converge. Along the inter-basin canal, numerous tributaries feature large confluence angles and significant flow discharge ratios. An experimental study investigated how these factors influence flow patterns, leading to proposed mitigation measures. This research employed a 1:50-scale physical river model and a sediment deposition model. It analyzed navigable flow conditions including velocity, flow patterns, the confluence ratio, the bottom elevation difference, and the confluence angle at the main channel–tributary junction. Focusing on the Jiuzhou River tributary entrance (Pinglu Canal), which has a large confluence ratio, significant bottom elevation difference, and wide confluence angle, this study tested two solutions: a single energy dissipator and a combined energy dissipator system. Sediment deposition modeling compared the effectiveness of these approaches. The results showed that implementing a steep slope with a three-stage stilling pool in the Jiuzhou River entrance section effectively manages confluences with large elevation differences, wide angles, and high flow discharge ratios. This configuration significantly improves entrance flow characteristics. Full article

Efficient cooling and heat recovery systems are becoming increasingly critical in large-scale commercial and industrial facilities, especially with the rising demand for sustainable energy solutions. Traditional air-conditioning and refrigeration systems often dissipate significant amounts of waste heat, which remains underutilized. This study addresses the challenge of harnessing low-potential waste heat from such systems to support fifth-generation district heating and cooling (5GDHC) networks, particularly in moderate-temperate regions like Flanders, Belgium. To evaluate the technical and economic feasibility of waste heat recovery, a methodology is developed that integrates established performance metrics—such as the energy efficiency ratio (EER), power usage effectiveness (PUE), and specific cooling demand (kW/t)—with capital (CapEx) and operational expenditure (OpEx) assessments. Empirical correlations, including regression analysis based on manufacturer data and operational case studies, are used to estimate equipment sizing and system performance across three operational modes. The study includes detailed modeling of data centers, cold storage facilities, and large supermarkets, taking into account climatic conditions, load factors, and thermal capacities. Results indicate that average cooling loads typically reach 58% of peak demand, with seasonal coefficient of performance (SCOP) values ranging from 6.1 to a maximum of 10.3. Waste heat recovery potential varies significantly across building types, with conversion rates from 33% to 68%, averaging at 59%. In data centers using water-to-water heat pumps, energy production reaches 10.1 GWh/year in heat pump mode and 8.6 GWh/year in heat exchanger mode. Despite variations in system complexity and building characteristics, OpEx and CapEx values converge closely (within 2.5%), demonstrating a well-balanced configuration. Simulations also confirm that large buildings operating above a 55% capacity factor provide the most favorable conditions for integrating waste heat into 5GDHC systems. In conclusion, the proposed approach enables the scalable and efficient integration of low-grade waste heat into district energy networks. While climatic and technical constraints exist, especially concerning temperature thresholds and equipment design, the results show strong potential for energy savings up to 40% in well-optimized systems. This highlights the viability of retrofitting large-scale cooling systems for dual-purpose operation, offering both environmental and economic benefits. Full article

In an attempt to reconciliate air-sea momentum flux estimates derived from open sea observations, from large eddy simulation output fields, and from wind-wave tank measurements, a series of dedicated experiments were conducted in the wind-wave tank of the Large Air-Sea Facility of Marseille, France. The turbulent friction velocity, upon which the momentum flux depends, was estimated from wind measurements by applying four classical methods including the eddy-covariance method and the inertial-dissipation method. The collected data were used to investigate some characteristics of the wave-influenced boundary layer that were predicted by previous simulations, and to quantify a wave-dependent term of the turbulent kinetic energy equation, the so-called imbalance term ${\varphi }_{\mathrm{imb}}$. Our results show that the turbulent stress decreases toward lower heights where the effect of waves is large, as in the simulations, and that ${\varphi }_{\mathrm{imb}}$ is in the range 0.3 to 0.7, which is comparable to the value found with open sea data (0.4). These preliminary results have to be confirmed with wave-following probes, because the estimated eddy-covariance flux slightly varied with height, thus it could not be strictly considered to be equal to a constant total flux. Full article

The tomato is among the crops with the most extensive cultivated area and greatest consumption in our nation; nonetheless, secondary salinization of facility soil significantly hinders the sustainable growth of facility agriculture. Melatonin (MT), as an innovative plant growth regulator, is essential in stress responses. This research used a hydroponic setup to replicate saline stress conditions. Different endogenous levels of melatonin (MT) were established by foliar spraying of 100 μmol·L⁻¹ MT, the MT synthesis inhibitor p-CPA (100 μmol·L⁻¹), and a combination of p-CPA and MT, to investigate the mechanism by which MT mitigates the effects of salt stress on the photosynthetic efficiency of tomato seedlings. Results indicated that after six days of salt stress, the endogenous MT content in tomato seedlings drastically decreased, with declines in the net photosynthetic rate and photosystem performance indices (PI_total and PI_abs). The OJIP fluorescence curve exhibited distortion, characterized by anomalous K-band and L-band manifestations. Exogenous MT dramatically enhanced the gene (TrpDC, T5H, SNAcT, and AcSNMT) expression of critical enzymes in MT synthesis, therefore boosting the level of endogenous MT. The application of MT enhanced the photosynthetic parameters. MT treatment decreased the fluorescence intensities of the J-phase and I-phase in the OJIP curve under salt stress, attenuated the irregularities in the K-band and L-band performance, and concurrently enhanced quantum yield and energy partitioning ratios. It specifically elevated φP_o, φE_o, and ψ_o, while decreasing φD_o. The therapy enhanced parameters of both the membrane model (ABS/RC, DI_o/RC, ET_o/RC, and TR_o/RC) and leaf model (ABS/CS_m, TR_o/CS_m, ET_o/CS_m, and DI_o/CS_m). Conversely, the injection of exogenous p-CPA exacerbated salt stress-related damage to the photosystem of tomato seedlings and diminished the beneficial effects of MT. The findings suggest that exogenous MT mitigates salt stress-induced photoinhibition by (1) modulating endogenous MT concentrations, (2) augmenting PSII reaction center functionality, (3) safeguarding the oxygen-evolving complex (OEC), (4) reinstating PSI redox potential, (5) facilitating photosynthetic electron transport, and (6) optimizing energy absorption and dissipation. As a result, MT markedly enhanced photochemical performance and facilitated development and salt stress resilience in tomato seedlings. Full article

Fluid dynamic noise produced by eddy disturbances and friction along pipe walls poses a significant challenge in natural gas transmission and distribution stations. (K)TS control valves are widely used in natural gas transmission and distribution stations across Southwest China and are among the primary sources of noise in these facilities. In this study, a 3D geometric model of the (K)TS valve was developed, and the gas flow characteristics were simulated to analyze the gas flow field and sound field within the valve under varying pipeline flow velocities, outlet pressures, and valve openings. The results demonstrate that accurate calculations of the 3D valve model can be achieved with a grid cell size of 3.6 mm and a boundary layer set to 3. The noise-generating regions of the valve are concentrated around the throttle port, valve chamber, and valve inlet. The primary factors contributing to the aerodynamic noise include high gas flow velocity gradients, intense turbulence, rapid turbulent energy dissipation, and vortex formation and shedding within the valve. An increase in inlet flow velocity intensifies turbulence and energy dissipation inside the valve, while valve opening primarily influences the size of vortex rings in the valve chamber and throttle outlet. In contrast, outlet pressure exerts a relatively weak effect on the flow field characteristics within the valve. Under varying operating conditions, the noise directivity distribution remains consistent, exhibiting symmetrical patterns along the central axis of the flow channel and forming six-leaf or four-leaf flower shapes. As the distance from the monitoring point to the valve increases, noise propagation becomes more concentrated in the vertical direction of the valve. These findings provide a theoretical basis for understanding the mechanisms of aerodynamic noise generation within (K)TS control valves during natural gas transmission, and can also offer guidance for designing noise reduction solutions for valves. Full article

Stepped spillways, as highly effective energy dissipation facilities, have been widely applied in hydraulic engineering. By introducing an inclination angle to the horizontal step surface, either energy dissipation efficiency or sediment transport capacity can be enhanced. The manner and size of vortices within the steps vary with changes in the inclination angle and spillway slope, enhancing energy dissipation through momentum exchange between the main flow and these vortices. This study, drawing upon data in the literature and numerical simulations, investigates the influence of a spillway slope and step inclination angle on the energy dissipation characteristics of inclined stepped spillways. Results indicate that the energy dissipation rate decreases with an increasing spillway slope while increasing with a greater upward inclination of the step’s horizontal surface. However, changes in both parameters show a limiting effect on vortex development. As the spillway slope decreases and the step inclination angle increases, the rate of vortex size expansion diminishes. Finally, an inclination/slope ratio is proposed to characterize the energy dissipation effect of inclined steps, and an empirical formula relating the energy dissipation rate to the relative critical depth, relative spillway height, and inclination/slope ratio is established, with errors controlled within 10%. Full article

Armor blocks are extensively deployed to shield vital coastal facilities against wave erosion. Evaluating the wave run-up and reflection under wave impact is essential for the engineering design of new ecological quadrangular hollow blocks. This study constructs a three-dimensional numerical model employing the open-source CFD software OpenFOAM-v2206 to analyze these processes for the new blocks. The model’s accuracy was confirmed by comparing its predictions with physical modelling tests. Model results accurately captured the variation in hydrodynamic parameters, as well as the energy dissipation properties of the new blocks. Sensitivity analysis indicated that both the wave reflection coefficients and run-up are considerably affected by mesh sizes, while velocity distributions and pressure fields were less affected by mesh. Finally, the model was utilized to examine how wave run-up and reflection for the new ecological quadrilateral hollow block are influenced by factors such as wave period, water depth, wave height, wave breaking characteristics, and wave steepness. The findings in this study provide valuable insights into novel design and safety assessment of new ecological quadrangular hollow blocks. Full article

It is highly desired yet challenging to develop advanced elastomers with excellent mechanical properties, including high strength and toughness. In this work, strong and tough rubber/rubber compound vulcanizates were facilely prepared by blending ethylene-propylene-methylene (EPM) and isoprene rubber (IR) together with dicumyl peroxide (DCP) and subsequent vulcanization, since both EPM and IR can be vulcanized synchronously by DCP and the well-crosslinked structure of EPM/IR vulcanizate presented a stable phase separation state. By tuning their composition, EPM/IR vulcanizates could present remarkably improved mechanical strength and toughness, as well as excellent energy dissipation and deformation recovery abilities. Furthermore, EPM/IR/SiO₂ nanocomposites with better properties were prepared by introducing silica nanoparticles into EPM/IR vulcanizates. It was found that the high toughness and strength of EPM/IR vulcanizates and EPM/IR/SiO₂ nanocomposites mainly resulted from the combination of stretchability of EPM and strain hardening of IR. Their excellent energy dissipation and deformation recovery abilities were related to the macromolecular characteristics of EPM and IR, compatibility between EPM and IR, and their crosslinking dynamics. Full article

The cyclic loading generated by injection and production operations in underground gas storage facilities can lead to fatigue damage to cement sheaths and compromise the integrity of wellbores. To investigate the influence of cyclic loading on the fatigue damage of well cement, uniaxial and triaxial loading tests were conducted at different temperatures, with maximum cyclic loading intensity ranging from 60% to 90% of the ultimate strength. Test results indicate that the compressive strength and elastic modulus of well cement subjected to monotonic loading under high-temperature and high-pressure (HTHP) testing conditions were 14–21% lower than those obtained under ambient testing conditions. The stress–strain curve exhibits stress–strain hysteresis loops during cyclic loading tests, and the plastic deformation capacity is enhanced at HTHP conditions. Notably, a higher intensity of cyclic loading results in more significant plastic strain in oil-well cement, leading to the conversion of more input energy into dissipative energy. Furthermore, the secant modulus of well cement decreased with cycle number, which is especially significant under ambient test conditions with high loading intensity. Within 20 cycles of cyclic loading tests, only the sample tested at a loading intensity of 90% ultimate strength under an ambient environment failed. For samples that remained intact after 20 cycles of cyclic loading, the compressive strength and stress–strain behavior were similar to those obtained before cyclic loading. Only a slight decrease in the elastic modulus is observed in samples cycled with high loading intensity. Overall, oil-well cement has a longer fatigue life when subjected to HTHP testing conditions compared to that tested under ambient conditions. The fatigue life of well cement increases significantly with a decrease in loading intensity and can be predicted based on the plastic strain evolution rate. Full article

The research and management of Industry 4.0 increasingly relies on accurate real-time quality data to apply efficient algorithms for predictive maintenance. Currently, Low-Power Wide-Area Networks (LPWANs) offer potential advantages in monitoring tasks for predictive maintenance. However, their applicability requires improvements in aspects such as energy consumption, transmission range, data rate and constant quality of service. Commonly used battery-operated IIoT devices have several limitations in their adoption in large facilities or heat-intensive industries (iron and steel, cement, etc.). In these cases, the self-heating nodes together with the appropriate low-power processing platform and industrial sensors are aligned with the requirements and real-time criteria required for industrial monitoring. From an environmental point of view, the carbon footprint associated with human activity leads to a steady rise in global average temperature. Most of the gases emitted into the atmosphere are due to these heat-intensive industries. In fact, much of the energy consumed by industries is dissipated in the form of waste heat. With this scenario, it makes sense to build heat transformation collection systems as guarantors of battery-free self-powered IIoT devices. Thermal energy harvesters work on the physical basis of the Seebeck effect. In this way, this paper gathers the methodology that standardizes the modelling and simulation of waste heat recovery systems for IoT nodes, gathering energy from any hot surface, such as a pipe or chimney. The statistical analysis is carried out with the data obtained from two different IoT architectures showing a good correlation between model simulation and prototype behaviour. Additionally, the selected model will be coupled to a low-power processing platform with LoRaWAN connectivity to demonstrate its effectiveness and self-powering ability in a real industrial environment. Full article

Offshore substations are important sustainable power infrastructures subjected to strong vibrations induced by complex environmental excitations such as wind, waves, and currents. To protect the structures and expensive facilities, lightweight vibration control devices are highly desirable in offshore substations. With a high-performance energy dissipation device, the inerter, the conventional Tuned Mass Damper (TMD) is upgraded for lightweight vibration control. The optimal parametric design and performance evaluation of single- and double-tuned vibration control devices is performed based on the H-norm criteria. The corresponding equivalent mass ratios of both single- and double-tuned vibration control devices are summarized and formulated in a systematical manner. Finally, the presented optimal design formulas, equivalent mass ratios, and control performances are validated by vibration control analyses on a practical offshore substation. The results show that inerter-based vibration control devices can be effectively equivalent to a TMD, with the equivalent mass ratio. The double-tuned inerter-based device could save 25% mass compared to a TMD. With a Tuned Mass Damper Inerter (TMDI), the responsibility for the mass could be shared with dual-end connected inerters. Meanwhile, the Tuned Viscous Mass Damper (TVMD) completely replaces the mass block with an inerter, which has a superior lightweight vibration control performance. Full article

Underground storage of natural gas has the characteristics of clean and low-carbon, and has the ability to provide a sustainable and stable supply. It is a very high-quality green energy that can increase the storage efficiency of gas storage through fracturing, achieving the sustainable development goal of “Carbon Peaking and Carbon Neutrality”. To improve the storage efficiency of natural gas, it is necessary to carry out refracturing. Moreover, it is of great significance to estimate the fracability of the potential refracturing formation. At present, research on fracability is mainly based on qualitative characterization or quantitative evaluation based on rock mechanics and fracturing construction parameters, which cannot fully reflect the rock composition and structure of each stage. Firstly, based on logging data, this paper analyzes the evolution laws of strain energy such as elastic properties, pre-peak dissipation energy, and post-peak fracture energy during the transition of rock materials from plastic deformation to brittle fracture from an energy perspective, and determines the key energy that affects the brittle characteristics of rocks. Secondly, a brittleness index evaluation approach has been established that can comprehensively reflect the mechanical properties of rocks during pre-peak deformation and post-peak damage stages. In addition, this article focuses on the impact of a reservoir stratigraphic environment by combining the influence of geo-stresses with the rock brittleness index, and proposes a new method for evaluating reservoir fracability. Finally, this paper conducts a study on the fracability evaluation of three wells in a gas storage facility in Eastern China. The results indicate that low modulus and fracability index are beneficial for fracturing, thereby improving the gas production and peak shaving ability of gas storage. Full article

The use of column-tree connections is common in controlled shop environments due to their cost-effectiveness in achieving ductile welds. Field bolts are also easy to install and inspect. However, there is currently no prequalification available for these connections, their performance is not fully understood, and the cost of aftermath repairs is still a major concern for owners. In this research, analytical and numerical studies were performed to assess the cyclic behavior considering the effects of the bolted splice location, bolt slippage, and splice plate thickness. Fourteen numerical models using the finite element method in ANSYS software were analyzed to evaluate the nonlinear behavior of moment connection configurations in terms of the strength, stiffness, ductility, energy dissipation, and overall cyclic response. The results showed that appropriately proportioned bolted splice connections can meet the requirements for prequalified moment connections. The models complied with the criteria established in AISC 358 and achieved flexural resistance that was higher than 80% of the beam plastic moment at 4% of the interstory drift ratio. The weakened plates concentrated the inelastic action, which allowed us to prevent the brittle behavior and damage to the column, welding, and other components of the moment connection. Complex geometries or specially fabricated parts were not required, providing a cost-effective way to control seismic-related damage. Also, required repairs are based on the replacement of standard parts, reducing operational detentions in facilities. Finally, the moment connection studied is classified as partially restrained (PR) according to the requirements established in AISC 360. Full article

Against the background of climate protection and the rising costs of a fossil-fuel-based energy supply, the interest in the energy performance and indoor climate of buildings in real operation is rising. This paper, therefore, deals with the indoor climate investigation of two medium-sized office buildings in Germany by taking measurements over a whole year. These relate to one new building and one refurbished building. Sensors of various types were installed and operated in a large number of office rooms, so that in total results are available for over 100 rooms, typically occupied by one or two persons. The analysis focuses on the indoor temperature in summer and the air quality in winter based on the CO₂ concentration. The comfort classes according to DIN EN 16798 including the adaptive comfort approach are used as a basis to cluster the results. Both buildings have movable sun protection and openable windows but no facilities for active cooling. They, thus, represent a large number of existing ‘low tech’ office buildings in Germany and central Europe. The results reflect the respective building concepts but also show a wide range between the rooms due to the user preferences and behaviour. The refurbished building shows better results, especially in terms of air quality but also in terms of summer room temperatures. This underlines the benefit of the targeted measures as a result of an analysis of the deficits in the existing building before the refurbishment. The additional measures for decentralised mechanical ventilation and passive cooling are having positive effects. As part of the projects, further measures to improve the indoor climate were investigated in both buildings. In one case, this involved CO₂ traffic lights to stimulate personal window ventilation in winter, and in the other, the use of newly developed individual ceiling fans supports convective heat dissipation on the human body during hot spells in summer. The positive effect could be demonstrated for both measures. Full article

In recent years, the number of high-voltage transmission lines has sharply increased with the rapid development of modern industry. However, a corona discharge phenomenon often occurs on the exposed high-voltage transmission lines, leading to energy loss and noise pollution. Herein, we have proposed a facile spraying method to prepare a superhydrophobic and thermally conductive coating to restrain the corona discharge phenomenon of high-voltage transmission lines, with vinyl silicone oil and hydrogen silicone oil as the main materials and modified boron nitride (BN) as a thermal conductive filler. The obtained composite coating exhibited superhydrophobicity, with a high water contact angle of 162°. In addition, the coating also showed a good self-cleaning capability, non-adhesion capability, mechanical stability, and chemical stability. Owing to the construction of the thermally conductive pathways with BN, the thermal conductivity of the coating reached 1.05 W/m·K, which was beneficial to quickly dissipating the heat generated by the current heating effect. Moreover, the corona losses of the positive and negative electrodes under simulated rainy conditions were decreased by 7.43% and 8.05%, respectively. The findings of our work have provided a new strategy to effectively restrain the corona discharge phenomenon of transmission lines, showing great application potential in the field of high-voltage power networks. Full article