Search Results (49)

This study investigates the differential settling behavior of binary particle suspensions through a combination of theoretical modeling and batch settling experiments. A classical zone-formation differential settling model is adopted, and a comprehensive experimental program is designed to generate data for model evaluation. Batch settling tests conducted using fine copper tailings and coarse silica sands show that distinct settling zones can be identified, and the solids’ concentrations of the particle species are consistent with theoretical predictions. However, the behavior within the sediment region differs from model assumptions, as a range of solids’ concentrations is observed, suggesting the presence of a transition zone rather than a sharp transition from the hindered settling region to a sediment with maximum solids’ concentration. Experimental observations of the sediment boundary also reveal a discrepancy between theoretical predictions and measured propagation velocities. This discrepancy is attributed to inter-species interactions arising from differential settling velocities, which are not accounted for in conventional models. The results highlight the limitations of widely used differential settling models and emphasize the importance of incorporating species–species interactions and transition zone behavior to improve the prediction of settling behavior in multi-species suspensions. Full article

The cylindrical hydrocyclone can be regarded as a special-shaped hydrocyclone comprising entirely cylindrical sections without conical sections, featuring a unique flat-bottom design combined with central discharge, which promotes substantial particle circulation flow in the separation chamber, directly affecting separation performance. A validated TFM model is employed to investigate the flow field and particle motion behavior in the cylindrical hydrocyclone. The results indicate that the distributions of tangential velocity, radial velocity, pressure, and pressure gradient in the cylindrical hydrocyclone are consistent with patterns observed in the conventional hydrocyclone. The flat-bottom design combined with the central discharge configuration of the cylindrical hydrocyclone results in two distinct axial velocity transitions in the bottom region, forming downward axial velocity flow around the air core. Accordingly, particles moving toward the spigot must pass through the internal swirling flow region, facilitating the fine particles entrained by the coarse particles to enter the internal swirling flow, reducing the misplacement of fine particles in the underflow. Simultaneously, coarse particles entrained by the internal swirling flow return to the external swirling flow region under centrifugal force, forming a substantial coarse particle circulation flow. As a result, a mass of coarse particles accumulates in the separation chamber, hindering the centrifugal settling of medium particles and resulting in an enlarged cut size and severe coarse particle misplacement. Full article

Direct power control (DPC) is widely recognized for its simplicity and fast dynamic response; however, conventional implementations based on hysteresis comparators suffer from critical limitations, including variable switching frequency and pronounced active power oscillations, which hinder their applicability in renewable and hybrid energy systems. To address these challenges, this study proposes a fractional-order predictive DPC strategy incorporating a fractional-order proportional–integral (FOPI) regulator to enhance dynamic performance and robustness. The proposed method is systematically evaluated against both a conventional proportional–integral-based DPC (PI-DPC) and existing fractional-order DPC approaches under identical operating conditions using MATLAB simulations. The results demonstrate that the proposed controller achieves a stabilized switching frequency while significantly improving DC-link voltage performance. Specifically, the proposed method reduces voltage ripples to 0.027 V compared to 0.094 V and 0.104 V for PI-DPC and FOPI-FOPI-DPC with space vector modulation (SVM), corresponding to improvements of 71.27% and 74.03%, respectively. The overshoot is also reduced to 0.75%, outperforming PI-DPC (1.25%) and FOPI-FOPI-DPC-SVM (1%), with improvements of 40% and 25%. In terms of dynamic response, the proposed approach achieves a fast response time of 0.06 s, representing a 40% improvement over PI-DPC, while maintaining comparable performance with other fractional-order methods. Additionally, the steady-state error is reduced to 0.04 V, achieving improvements of 60% and 50% compared to PI-DPC and FOPI-FOPI-DPC-SVM, respectively. Although the settling time shows marginal variation, the overall system exhibits enhanced stability and robustness. These outcomes highlight the effectiveness of integrating fractional-order control with predictive strategies, offering a robust and practically viable solution for real-world hybrid power systems that integrate renewable generation and energy storage. Full article

Non-equilibrium suspended sediment transport is the most general state in engineering practice. Earlier analytical and numerical models for non-equilibrium suspended sediment transport were primarily designed for specific case studies and lack universal applicability. This work aims to develop a generalized two-dimensional (2D) numerical model based on the incompressible smoothed particle hydrodynamics (ISPH) approach for simulating non-equilibrium suspended sediment transport. The model integrates a generalized bottom boundary condition that accounts for both deposition velocity and equilibrium concentration. The impact of turbulence, as well as the hindered settling effect, is also included in the model. The efficacy of the model was assessed using results from analytical or semi-analytical models under 1D unsteady and 2D steady sediment transport modes, as well as from laboratory experiments for 2D unsteady sediment transport. This model reveals the physical mechanism of the hindered settling effect. The effect is most significant in the main suspension zone, where particles interact frequently. In the near-bottom zone, it is limited by physical constraints, and the settling velocity reaches its minimum. In the top zone, the effect is limited by the very low particle concentration, where particle interactions are negligible. The model also captures the different responses caused by different distributions of the turbulent viscosity coefficient and the bottom reference concentration. Full article

Effective treatment of coal slime water is essential for sustainable coal preparation plant operation but hindered by the stable suspension of fine, negatively charged particles. To address this, a novel star-shaped inorganic–organic hybrid polymer (aluminum hydroxide-polyacrylamide, Al-PAM) was synthesized via in situ polymerization. Its performance was systematically compared with well-established coagulants/flocculants—polyaluminum chloride (PAC), non-ionic polyacrylamide (NPAM), and their binary combination through settling tests and quartz crystal microbalance with dissipation monitoring (QCM-D). The results showed a positive correlation between the molecular weight of Al-PAM and its flocculation efficiency. The optimal variant, Al-PAM-442, achieved an exceptionally high initial settling rate (50.4 m/h) and low supernatant turbidity (45.77 NTU) at an ultralow dosage of 6 mg/L. QCM-D analysis elucidated the mechanism: Al-PAM forms a thick, soft, and irreversibly adsorbed hydrated layer on silica, enabling strong electrostatic anchoring and effective polymer bridging. In contrast, PAC adsorption was reversible, while NPAM formed a thin, compact film with poor bridging capacity. Although the combined PAC/NPAM system showed synergistic performance, it required a significantly higher dosage (70 mg/L). This study demonstrates that the star-shaped Al-PAM architecture successfully integrates charge neutralization and bridging into a single molecule, offering a highly efficient and practical solution for industrial coal slurry dewatering. Full article

The accelerating pace of global population growth, urbanization, and industrialization is exerting considerable pressure on freshwater resources. In developing countries, where infrastructure constraints often hinder the adoption of advanced treatment technologies, cost-effective and efficient wastewater solutions are essential. Algal–bacterial bioremediation represents a promising, eco-friendly method for removing organic pollutants through biological processes. This study evaluates a hybrid treatment system composed of three ponds: a covered anaerobic pond for organic matter digestion, a microalgal pond equipped with rotating biological contactors (RBCs) that facilitate interactions between heterotrophic bacteria and diatoms, and a final settling pond. Granular activated carbon embedded within the RBC enhances biofilm formation by attracting heterotrophic bacteria, thereby increasing treatment efficiency. Under optimal conditions—10 g of activated carbon and 1.7 d hydraulic retention time—the system achieved removal efficiencies of 95.8% for total suspended solids (TSS), 96.3% for turbidity, 85% for biological oxygen demand (BOD), and 99.9% for Escherichia coli. Bacteriological analysis showed complete removal of fecal coliform and total coliform. The characteristics of the outflow treated wastewater are 3 mg/L, 0.9 NTU, and 3.2 mg/L for TSS, turbidity, and BOD, respectively, while E. coli detection is under detection limit. The treated effluent complies with Category A for the reuse of treated wastewater in the Egyptian code for the reuse of treated municipal wastewater for agricultural purposes, offering a scalable and sustainable solution for wastewater management in resource-constrained regions. Full article

Drill pipe pullback gravel packing is a novel sand control method for marine natural gas hydrate reservoirs, enabling rapid and uniform filling by synchronizing fluid injection with pipe retraction. However, the complex liquid–solid two-phase flow mechanisms and parameter sensitivities in this dynamic process remain unclear. To address this gap, a coupled Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) approach is adopted in accordance with the trial production requirements in the South China Sea. This investigation systematically analyzes the relative contributions of injection rate (0.8–2.2 m³/min) and sand-carrying ratio (30–60%) to the packing effectiveness. Additionally, the effects of carrier fluid viscosity and drill pipe pullback speed are explored. Results show that injection rate and sand-carrying ratio positively affect performance, with sand-carrying ratio as the decisive factor, exhibiting an impact approximately 73 times greater than that of the injection rate. Optimal parameters in this study are injection rate of 2.2 m³/min and sand-carrying ratio of 60%, which yield the highest gravel volume fraction and stable bed height. Furthermore, it is also found that while increasing carrier fluid viscosity improves bed height, excessive viscosity hinders particle settling and compaction. Similarly, a trade-off exists for the pullback speed to balance packing density and pipe burial risks. These findings provide a theoretical basis for optimizing sand control operations in hydrate trial productions. Full article

Gradually replacing fossil fuels with renewable energy constitutes a long-term strategy for achieving sustainable development. In the short term, it is necessary to explore unconventional oil and gas resources to support current economic sustainability and to secure essential time for the energy transition. With the continuous growth in global energy demand, unconventional resources such as shale oil and shale gas have become important alternative energy sources. Lacustrine mudrock successions demonstrate significant potential for unconventional oil and gas resources. However, the unclear understanding of how paleoenvironmental evolution influences lithofacies and organic matter enrichment restricts the optimization of shale oil reservoirs and evaluation of shale oil resources, thereby hindering the progress of lacustrine shale oil exploration and development. The mudrocks in the Chang 7 Member of the Triassic Yanchang Formation, Ordos Basin, were deposited in a pro-delta to a deep lacustrine environment and are rich in shale oil resources. Through petrographic, sedimentological, sequence stratigraphic, and geochemical analyses, this study reveals how the evolution of the paleoenvironment controlled the development of mudrocks and the enrichment of organic matter, and establishes a sedimentary model for freshwater lacustrine systems. Six lithofacies have been identified within the mudrock interval of the Chang 7 Member. According to the T-R (transgressive–regressive) sequence model, the Chang 7 Member can be subdivided into three fourth-order sequences, termed Parasequence Set 1–3 (PPS1–3). Mudrock is predominantly developed in the fourth-order sequences PSS1 and PSS2. The PSS1 and the lower part of PSS2 consist of lithofacies 1–4, representing semi-deep to deep lacustrine deposits. The upper part of PSS2 develops lithofacies 5, representing shallow lacustrine to pro-delta deposits. Fluctuations of the lake level controlled the vertical stacking of lithofacies and the transition in depositional mechanisms. During lake-level rise, bottom currents shifted to suspension settling, whereas the opposite occurred during lake-level fall. The organic matter is derived from algae, and its enrichment is jointly controlled by productivity and the redox conditions. Volcanic–hydrothermal activity and a humid climate promoted high productivity in the water body. This high productivity promotes dyoxic conditions in the bottom water. Fourth-order relative lake-level fluctuations also influence organic matter enrichment. During lake-level rise, increased productivity coupled with reduced consumption and dilution favors organic matter enrichment. Conversely, organic matter accumulation is inhibited during lake-level fall. Ultimately, a depositional model for a freshwater lacustrine basin under a humid to semi-humid climatic background was established. This paper elucidates the influence of sedimentary environment on mudrock lithofacies and organic matter enrichment, providing a theoretical basis for optimizing shale oil reservoir selection and resource assessment, thereby promoting efficient exploration and low-carbon development of shale oil in lacustrine basins. Full article

Dredged sludge is characterized by a high water content, low permeability, and poor load-bearing capacity, which hinder its sustainable utilization as an engineering filler. During the stabilization process using vacuum preloading (VP), fine-grained sludge readily clogs drainage channels, thereby prolonging consolidation duration and compromising drainage efficiency. To address these persistent challenges, this study proposes an improved method that combines electroosmosis, VP, and polyacrylamide (PAM) to enhance the consolidation performance of dredged sludge. Column settling experiments demonstrated that the optimal application dosages of anionic polyacrylamide (APAM) and calcium chloride (CaCl₂) were 0.25% and 4.0% of dry sludge mass, respectively. Excessive dosage of either APAM or CaCl₂ disturbed the agglomeration and sedimentation of fine-grained particles due to surface charge inversion. Electroosmotic VP (EVP) facilitated the directional movement of pore water, which increased the cumulative water discharge mass by 37.3%. The combination of APAM and CaCl₂ enhanced particle flocculation via adsorption and bridging effects, significantly improving soil permeability and dewatering performance. Driven by an electric field, Ca²⁺ ions transported water molecules toward the cathode. Subsequently, these Ca²⁺ ions participated in reactions to generate cementitious agents. Compared with VP, this integrated method increased the sludge shear strength by 108.1% and produced a much denser microstructure. Full article

This study explores the application of high-silica flux ore in copper smelting and converting processes at the Zhezkazgan Copper Smelting plant. Pilot-scale experiments and SEM analyses were performed to assess its influence on slag composition, temperature regime, and metal recovery. The results demonstrated that replacing conventional flux with high-silica ore reduced flux consumption by 19%, increased converter slag temperature from 1124 to 1174 °C, and decreased copper content in converter slag from 10% to 4.5%. SEM micro-analysis revealed the formation of lead-containing silicate rims around matte inclusions, which hinder their settling at low temperatures. However, when the slag temperature exceeded 1400 °C, these rims were destroyed, facilitating separation and reducing residual copper. These findings highlight the potential of high-silica fluxes (>90% SiO₂) to improve both energy efficiency and metal recovery in process of copper matte converting, offering practical recommendations for industrial operations. Full article

This study investigates sedimentation dynamics and microstructural evolution of silty clay and mucky sediments from the immersed tube tunnel trench of the Shunde Tanzhou Waterway. Experiments examined different initial unit weights (11.5–12.6 kN/m³) and heights (10–60 cm) through sedimentation tests (N = 30, representing five heights × three unit weights × two soil types) and scanning electron microscopy (SEM) imaging. Results identified two sedimentation patterns: consolidation (inverse “S” curve) and hindered (three-stage) types. Key findings reveal that silty clay exhibits height-dependent transition between patterns (critical height = 30 cm at γ = 12.6 kN/m³). Mucky soil demonstrates stable hindered settlement across conditions (rate = 0.09 ± 0.01 cm/min at γ = 12.0 kN/m³). Moisture distribution analysis reveals that unstable structures in low-unit-weight slurries exhibit slow drainage and steady moisture content changes. Microstructural analysis uncovered height-dependent porosity increases and pore complexity in mucky soils, alongside reduced honeycomb-like cavities and enhanced particle aggregation in silty clay under lower unit weights. These results provide novel insights into the interplay between initial slurry conditions and sedimentation behavior, offering a theoretical foundation for optimizing dredging strategies and ensuring long-term sediment stability in immersed tube tunnel projects. Full article

This paper addresses inherent limitations in unmanned aerial vehicle (UAV) undercarriages hindering vertical takeoff and landing (VTOL) capabilities on uneven slopes and obstacles. Robotic landing gear (RLG) designs have been proposed to address these limitations; however, existing designs are typically limited to ground slopes of 6–15°, beyond which rollover would happen. Moreover, articulated RLG concepts come with added complexity and weight penalties due to multiple drivetrain components. Previous research has highlighted that even a minor 3-degree slope change can increase the dynamic rollover risks by 40%. Therefore, the design optimization of robotic landing gear for enhanced VTOL capabilities requires a multidisciplinary framework that integrates static analysis, dynamic simulation, and control strategies for operations on complex terrain. This paper presents a novel, hybrid, compliant, belt-driven, three-legged RLG system, supported by a multidisciplinary design optimization (MDO) methodology, aimed at achieving enhanced VTOL capabilities on uneven surfaces and moving platforms like ship decks. The proposed system design utilizes compliant mechanisms featuring a series of three-flexure hinges (3SFH), to reduce the number of articulated drivetrain components and actuators. This results in a lower system weight, improved energy efficiency, and enhanced durability, compared to earlier fully actuated, articulated, four-legged, two-jointed designs. Additionally, the compliant belt-driven actuation mitigates issues such as backlash, wear, and high maintenance, while enabling smoother torque transfer and improved vibration damping relative to earlier three-legged cable-driven four-bar link RLG systems. The use of lightweight yet strong materials—aluminum and titanium—enables the legs to bend 19 and 26.57°, respectively, without failure. An animated simulation of full-contact landing tests, performed using a proportional-derivative (PD) controller and ship deck motion input, validate the performance of the design. Simulations are performed for a VTOL UAV, with two flexible legs made of aluminum, incorporating circular flexure hinges, and a passive third one positioned at the tail. The simulation results confirm stable landings with a 2 s settling time and only 2.29° of overshoot, well within the FAA-recommended maximum roll angle of 2.9°. Compared to the single-revolute (1R) model, the implementation of the optimal 3R Pseudo-Rigid-Body Model (PRBM) further improves accuracy by achieving a maximum tip deflection error of only 1.2%. It is anticipated that the proposed hybrid design would also offer improved durability and ease of maintenance, thereby enhancing functionality and safety in comparison with existing robotic landing gear systems. Full article

This study presents a novel unresolved SPH-DEM coupling framework to investigate the complex interactions between rising gas bubbles and sinking solid particles in multiphase systems. Traditional numerical methods often struggle with large deformations, multiphase interfaces, and computational efficiency when simulating dense particle-laden flows. To address these challenges, the proposed model leverages SPH’s Lagrangian nature to resolve fluid motion and bubble dynamics, while the DEM captures particle–particle and particle–bubble interactions. An unresolved coupling strategy is introduced to bridge the scales between fluid and particle phases, enabling efficient simulations of large-scale systems with discrete bubbles/particles. The model is validated against benchmark cases, including single bubbles rising and single particle’s sedimentation. Simulation studies reveal the effects of particle/bubble number and initial distance on phase interaction patterns and clustering behaviors. Results further illustrate the model’s capability to capture complex phenomena such as particle entrainment by bubble wakes and hindered settling in dense suspensions. The framework offers a robust and efficient tool for optimizing industrial processes like mineral flotation, where bubble–particle dynamics play a critical role. Full article

Copper-containing sludge and spent petrochemical catalyst (SPC) were investigated for recovering palladium (Pd) and silver (Ag). Increasing the mixing ratio of alumina-based SPC leads to reduced recovery rates at 1500 °C. Specifically, as the SPC mixing ratio increases from 10% to 30%, the recovery rate of Pd and Ag sharply decreases to 62.1% and 91.0%, respectively. This is attributed to an increase in the slag viscosity as well as to the higher sulfur content in the metal phase by decreasing the CaO/Al₂O₃ ratio of the slag. An increase in the slag viscosity causes a decrease in the metal recovery, as it lowers the settling velocity of metal droplets, resulting in imperfect metal separation, i.e., an increase in physical loss. Additionally, the presence of sulfur at the slag–metal interface was found to reduce interfacial tension, facilitating the entrapment of copper droplets within the slag. This further hindered phase separation and contributed to an increase in physical loss. This study highlights that physical loss is more serious in metal recovery rather than chemical loss, which is dependent on the thermochemical solubility of the target metals in the slag. The results emphasize the need for the precise control of slag properties to maximize the metal recovery processes in conjunction with a mitigation of CO₂ emissions. Full article

The morphological characteristics and surface roughness of substrata can significantly affect the settlement behaviour of planktonic larvae and the post-settlement survival of benthic organisms, such as mussels. Despite widespread recognition of these effects on ecological and aquaculture processes, species-specific complexities and limited research hinder a comprehensive understanding of the phenomenon and the potential to harness its application. In this study, the settlement of juvenile green-lipped mussels (Perna canaliculus; 0.32–3.59 mm shell length) on 42 different custom-designed artificial substrata with varied branch widths and surface microstructures were compared. Mussels smaller than 0.99 mm in shell length exhibited a clear preference for substrates with a thinner branch width (1.6 mm), wider roughness width (3.2 mm), and shorter roughness height (0.4 mm) on both V-shaped and squared-shaped surface microstructures. In contrast, for mussels larger than 1 mm, only the branch width of artificial substrata significantly influenced mussel attachment, while millimetre-scale surface features had no measurable effect. These findings indicate that, at the millimetre scale, the attachment of mussels > 1 mm does not conform to the surface contact theory, which proposes that settling organisms prefer substrates with microstructures that maximize their surface contact. Overall, a thinner branch width consistently yielded higher attachment densities, underscoring its dominant role. Our results reveal significant opportunities for optimizing the design of artificial substrata in mussel aquaculture, such as spat catching and nursery ropes, potentially improving seed collection efficiency and reducing the subsequent loss of seed mussels during their culture on mussel farms. Full article