Search Results (375)

A multiphase model of hydrothermal liquefaction (HTL) using the computational fluid dynamics coupling discrete element method (CFD-DEM) is used to simulate biocrude oil production from sludge flocs in a continuous stirred tank reactor (CSTR). Additionally, the influence of the agitator speed and the slurry flow rate on dynamic biocrude oil production is investigated through full transient CFD analysis in a scaled-up CSTR study. The kinetics of the HTL mechanism as a function of temperature, pressure, and residence time distribution were employed in the model through a user-defined function (UDF). The multiphysics simulation of the HTL process in a stirred tank reactor using the Lagrangian–Eulerian (LE) approach, along with a standard k-ε turbulence model, integrated HTL kinetics. The simulation accounts for particle–fluid interactions by coupling CFD-derived hydrodynamic fields with discrete particle motion, enabling prediction of individual particle trajectories based on drag, buoyancy, and interphase momentum exchange. The three-phase flow using a compressible non-ideal gas model and multiphase interaction as design requirements increased process efficiency in high-pressure and high-temperature model conditions. Full article

Vertical low-permeability barriers are widely used to improve the stability and seepage resistance of flood embankments. The present study evaluates three barrier technologies—vibrating beam slurry walls (VBSWs), deep soil mixing (DSM), and low-pressure grout injection (LPG)—through a series of consolidated drained triaxial tests and permeability coefficient tests on soil samples collected from the sites where different barrier installation technologies were used. All three barrier installation methods produced substantial improvements in both mechanical and hydraulic performance: the effective angle of internal friction (φ′) increased by 3–6° in samples with a plasticity index near 3.5%, and coefficients of permeability dropped from 10⁻⁸–10⁻⁷ m/s in untreated soils to below 10⁻⁹ m/s in treated specimens. The key finding of the study is that the barrier performance varies by the technology and the soil type. According to the result, DSM is the most effective technology used in clay-rich soils (φ′ increased up to 4°); LPG achieved the lowest permeability (7 × 10⁻¹¹ m/s) in granular soils; and VBSWs balanced strength and impermeability, most effective in silty sands. Flow-pump tests further demonstrated that treated soils required much longer to stabilize under a constant flow rate and could sustain higher hydraulic gradients before reaching equilibrium. These findings show the importance of matching barrier technology to soil plasticity and liquidity characteristics and highlight saturation as essential for reliable laboratory evaluation. The results provide a scientific basis for selecting and designing vertical barriers in flood-preventing infrastructure, offering performance benchmarks for improving hydraulic and geotechnical structures. Full article

Alkanolamine additives play a critical role in enhancing the early process performance of cement slurries, thereby improving construction efficiency and structural durability. This study systematically evaluates the effects of ethanolamine (EA), diethanolamine (DEA), and triethanolamine (TEA) on cement slurry properties, including the thickening time, rheology, density, shrinkage, and hydration kinetics. Clear structure–activity relationships are established based on the findings. The experimental analysis demonstrated that increasing the hydroxyl group count in the alkanolamines significantly accelerated cement hydration. At a dosage of 1.0%, the thickening time of the cement slurry was significantly shortened to 125 min (EA), 15 min (DEA), and 12 min (TEA), respectively. Concomitantly, a reduction in fluidity was observed, with flow diameters measuring 15.8 cm (EA), 14.6 cm (DEA), and 14.1 cm (TEA). The rheological analysis revealed that the alkanolamine additives significantly increased the consistency coefficient (K) and decreased the flowability index (n) of the slurry, with TEA exhibiting the most pronounced effect. The density measurements confirmed the enhanced settlement stability, as the density differences diminished to 0.1 g/cm³ at the optimal dosages (0.6% TEA and 0.8% DEA). The hydration degree analysis indicated a hydration rate acceleration of up to 32% relative to plain slurry, attributed to the hydroxyl-facilitated promotion of Ca(OH)₂ formation and C₃S dissolution. The XRD analysis confirmed that the alkanolamines modified the reaction kinetics without inducing phase transformation in the hydration products. Crucially, the hydroxyl group count governed the performance: a higher hydroxyl density intensified Ca²⁺/Al³⁺ complexation, thereby reducing ion mobility and accelerating setting. These findings establish a molecular design framework for alkanolamine-based additives that balances early process performance development with practical workability. The study advances sustainable cement technology by enabling targeted optimization of rheological and mechanical properties in high-demand engineering applications. Full article

Erosive wear from suspended sediments significantly threatens the structural integrity and efficiency of composite tidal turbine blades. This study develops a novel framework for predicting erosion in FR4 glass fibre-reinforced polymers (GFRPs)—materials increasingly adopted for marine renewable energy components. While erosion models exist for metals, their applicability to heterogeneous composites with unique failure mechanisms remains unvalidated. We calibrated the Oka erosion model specifically for FR4 using a complementary experimental–computational approach. High-velocity slurry jet tests (12.5 m/s) were conducted at a 90° impact angle, and erosion was quantified using both gravimetric mass loss and surface profilometry. It revealed a distinctive W-shaped erosion profile with 3–6 mm of peak material removal from the impingement centre. Concurrently, CFD simulations employing Lagrangian particle tracking were used to extract local impact velocities and angles. These datasets were combined in a constrained nonlinear optimisation scheme (SLSQP) to determine material-specific Oka model coefficients. The calibrated coefficients were further validated on an independent 45° impingement case (same particle size and flow conditions), yielding 0.0143 g/h predicted versus 0.0124 g/h measured (15.5% error). This additional case confirms the accuracy and feasibility of the predictive model under input conditions different from those used for calibration. The calibrated model achieved strong agreement with measured erosion rates (R² = 0.844), successfully capturing the progressive matrix fragmentation and fibre debonding, the W-shaped erosion morphology, and highlighting key composite-specific damage mechanisms, such as fibre detachment and matrix fragmentation. By enabling the quantitative prediction of erosion severity and location, the calibrated model supports the optimisation of blade profiles, protective coatings, and maintenance intervals, ultimately contributing to the extended durability and performance of tidal turbine systems. This study presents a procedure and the output of calibration for the Oka erosion model, specifically for a composite material, providing a transferable methodology for erosion prediction in GFRPs subjected to abrasive marine flows. Full article

Slurry-based additive manufacturing (AM) enables the fabrication of dense and complex ceramic components through the layer-by-layer deposition of high-solid-content slurries. However, the reliable formation of uniform, defect-free slurry layers remains a bottleneck for process stability and final part quality. In this study, the slot-die coating window for alumina slurry (50 wt%, viscosity = 34 Pa·s) was systematically investigated using volume-of-fluid simulations and experiments, with coating speed (0.7–2.8 mm/s), flow rate (0.6–0.8 mL/min), and coating gap (200–400 μm) as key variables. The coating process exhibited three distinct regimes, namely overflow, stable, and unstable, depending on process conditions. For a coating gap of 200 μm on a glass substrate, stable bead formation was observed over the widest coating speed range without overflow or air entrainment. At higher speeds, dynamic wetting failure induced air entrainment and bead breakage, while lower speeds led to overflow defects. When coating on a dried alumina layer (contact angle, CA = 137$°$), the stable window narrowed significantly compared to the glass substrate (CA = 66.7$°)$, highlighting the substantial influence of substrate wettability on coating stability and defect formation. The results derived in this work offer practical guidance for optimizing process parameters to achieve uniform, defect-free films in multilayer ceramic AM. Full article

The vortex-induced vibration (VIV) dynamics of commercial-scale deep-sea mining risers with complex component arrangements (pumps, buffer stations, buoyancy modules) remain insufficiently explored, especially for 6000 m systems with nonlinear tension. This study investigates VIV control strategy by adjusting tension for a nonlinear riser system using the Iwan-Blevins wake oscillator model integrated with Morison equation-based analysis. An analytical model incorporating four typical current profiles was established to quantify the dynamic response under different flow velocities, internal flow density, and structural parameters. Increased buffer station mass effectively suppressed drift distance (over 35% reduction under specific conditions) by regulating axial tension. Dynamic comparisons demonstrated distinct VIV energy distribution patterns under different current conditions. Spectral analysis revealed that the vibration follows Strouhal vortex shedding lock-in principles. Spatial modal differentiation was observed due to nonlinear variations in velocity profiles, pipe diameters, and axial tension, accompanied by multi-frequency resonance, coexistence of standing and traveling waves, and broadband resonance with amplitude surges under critical velocities (1.75 m/s in Current-B). This study proposes to control the VIV amplitude by adjusting internal flow density and buffer mass, which is proved effective for reducing vibrations in upper (0–2000 m) risers. It validates vibration amplitude and frequency control through current velocity, buffer mass and slurry density regulation in a nonlinear riser system. Full article

Synchronous grouting slurry is widely used in shield tunnel construction to fill the gaps between stratum and shield tail segments. However, as grout is nearly liquid in the initial stages, the tunnel lining segments recently separated from the shield tail are easily affected by the upward buoyancy generated by grout, causing issues such as longitudinal misalignment and opening of ring joints. Therefore, studying the upward buoyancy characteristics of synchronous grout is crucial. In this study, floating characterisation parameters of grout were investigated using buoyancy model tests, orthogonal tests, and comprehensive tests. The floating characterisation parameters are affected by distribution ratio and types of each grout component. The relationship between the floating characterisation parameters of grout and buoyancy was established. The results show that density, flow index, and shear strength can be used as the floating characterisation parameters. Binder–sand and water–binder ratios have the largest impact on the density. The bentonite–water ratio exerts a primary influence on the flow index, while the water–binder ratio contributes a secondary effect. In addition, bentonite–water and binder–sand ratios have the greatest effect on the shear strength. Furthermore, the particle size of sand and type of bentonite considerably influence the flow index and shear strength. A high-shear grout using well-graded fine sand and a high mesh of sodium bentonite was considered in this study. When the content of bentonite exceeds 7% (P2.2), Archimedes’ law is not applicable for calculating the upward buoyancy of grout. Buoyancy supply rate exhibits gradual enhancement with flow index elevation, yet with diminishing growth rates. Full article

The increasing depth of coal mine construction has led to complex geological conditions involving high ground stress and elevated groundwater levels, presenting new challenges for water-sealing technologies in rock microfissure grouting. This study investigates ultrafine cement grouting in microfissures through systematic analysis of slurry properties and grouting simulations. Through systematic analysis of ultrafine cement grout performance across water–cement (W/C) ratios, this study establishes optimal injectable mix proportions. Through dedicated molds, sandstone-like microfissures with 0.2 mm apertures and controlled roughness (JRC = 0–2, 4–6, 10–12) were fabricated, and instrumented with fiber Bragg grating (FBG) sensors for real-time strain monitoring. Triaxial stress-permeation experiments under 6 and 7 MPa confining pressures quantify the coupled effects of fissure roughness, grouting pressure, and confining stress on volumetric flow rate and fissure deformation. Key findings include: (1) Slurry viscosity decreased monotonically with higher W/C ratios, while bleeding rate exhibited a proportional increase. At a W/C ratio = 1.6, the 2 h bleeding rate reached 7.8%, categorizing the slurry as unstable. (2) Experimental results demonstrate that increased surface roughness significantly enhances particle deposition–aggregation phenomena at grouting inlets, thereby reducing the success rate of grouting simulations. (3) The volumetric flow rate of ultrafine cement grout decreases with elevated roughness but increases proportionally with applied grouting pressure. (4) Under identical grouting pressure conditions, the relative variation in strain values among measurement points becomes more pronounced with increasing roughness of the specimen’s microfissures. This research resolves critical challenges in material selection, injectability, and seepage–deformation mechanisms for microfissure grouting, establishing that the W/C ratio governs grout performance while surface roughness dictates grouting efficacy. These findings provide theoretical guidance for water-blocking grouting engineering in microfissures. Full article

Subcooling-based ice slurry production faces challenges in terms of energy efficiency and operational stability, which limit its applications for large-scale cold energy storage. A thermodynamic model is established to investigate the effects of key control parameters, including evaporation temperature, condensation temperature, subcooling degree, water flow rate, type of refrigerant, and adiabatic compression efficiency. The results show that using the refrigerant R161 achieves the highest energy efficiency, indicating that R161 is the optimal refrigerant in this research. When the evaporation and condensation temperatures are −10 °C and 30 °C, respectively, the system achieves the maximum comprehensive performance coefficient of 2.43. Moreover, under a flow velocity of 0.8 m/s and a temperature of 0.5 °C, the system achieves a peak ice production rate of 45.28 kg/h. A high water temperature and high flow velocity would significantly degrade the system’s ice production capacity. This research provides useful guidance for the design, optimization, and application of ice slurry-based cold energy storage systems. Full article

HPMC, regulating slurry properties, is widely used in cement-based materials. Research on the application of HPMC in gangue slurry is still in its early stages. Moreover, the interactive effects of various factors on gangue slurry performance have not been thoroughly investigated. The work examined the effects of slurry concentration (X₁), maximum gangue particle size (X₂), and HPMC dosage (X₃) on slurry performance using response surface methodology (RSM). The microstructure of the slurry was characterized via scanning electron microscopy (SEM) and polarized light microscopy (PLM), while low-field nuclear magnetic resonance (LF-NMR) was employed to analyze water distribution. Additionally, industrial field tests were conducted. The results are presented below. (1) X₁ and X₃ exhibited a negative correlation with layering degree and slump flow, while X₂ showed a positive correlation. Slurry concentration had the greatest impact on slurry performance, followed by maximum particle size and HPMC dosage. HPMC significantly improved slurry stability, imposing the minimum negative influence on fluidity. Interaction terms X₁X₂ and X₁X₃ significantly affected layering degree and slump flow, while X₂X₃ significantly affected layering degree instead of slump flow. (2) Derived from the RSM, the statistical models for layering degree and slump flow define the optimal slurry mix proportions. The gangue gradation index ranged from 0.40 to 0.428, with different gradations requiring specific slurry concentration and HPMC dosages. (3) HPMC promoted the formation of a 3D floc network structure of fine particles through adsorption-bridging effects. The spatial supporting effect of the floc network inhibited the sedimentation of coarse particles, which enhanced the stability of the slurry. Meanwhile, HPMC only converted a small amount of free water into floc water, which had a minimal impact on fluidity. HPMC addition achieved the synergistic optimization of slurry stability and fluidity. (4) Field industrial trials confirmed that HPMC-optimized gangue slurry demonstrated significant improvements in both stability and flowability. The optimized slurry achieved blockage-free pipeline transportation, with a maximum spreading radius exceeding 60 m in the goaf and a maximum single-borehole backfilling volume of 2200 m³. Full article

Sustainable deepwater drilling for oil and gas offers significant potential. In this work, we synthesized a nanoscale collapse-prevention agent by grafting didecyldimethylammonium chloride onto spherical nano-silica and characterized it using Fourier-transform infrared spectroscopy, thermogravimetric analysis, zeta-potential, and particle-size measurements, as well as SEM and TEM. Adding 1 wt% of this agent to a bentonite slurry only marginally alters its rheology and maintains acceptable low-temperature flow properties. Microporous-membrane tests show filtrate passing through 200 nm pores drops to 55 mL, demonstrating excellent plugging. Core-immersion studies reveal that shale cores retain integrity with minimal spalling after prolonged exposure. Rolling recovery assays increase shale-cutting recovery to 68%. Wettability tests indicate the water contact angle rises from 17.1° to 90.1°, and capillary rise height falls by roughly 50%, reversing suction to repulsion. Together, these findings support a synergistic plugging–adsorption–hydrophobization mechanism that significantly enhances wellbore stability without compromising low-temperature rheology. This work may guide the design of high-performance collapse-prevention additives for safe, efficient deepwater drilling. Full article

Understanding the rheological properties of fresh cement slurries is essential to maintain optimal pumpability, achieve dependable zonal isolation, and preserve long-term well integrity in oil and gas cementing operations and the 3D printing cement and concrete industry. However, accurately and efficiently modeling the rheological behavior of cement slurries remains challenging due to the complex fluid properties of fresh cement slurries, which exhibit non-Newtonian and thixotropic behavior. Traditional numerical solvers typically require mesh generation and intensive computation, making them less practical for data-scarce, high-dimensional problems. In this study, a physics-informed neural network (PINN)-based framework is developed to solve the governing equations of steady-state cement slurry flow in a tilted channel. The slurry is modeled as a non-Newtonian fluid with viscosity dependent on both the shear rate and particle volume fraction. The PINN-based approach incorporates physical laws into the loss function, offering mesh-free solutions with strong generalization ability. The results show that PINNs accurately capture the trend of velocity and volume fraction profiles under varying material and flow parameters. Compared to conventional solvers, the PINN solution offers a more efficient and flexible alternative for modeling complex rheological behavior in data-limited scenarios. These findings demonstrate the potential of PINNs as a robust tool for cement slurry rheological modeling, particularly in scenarios where traditional solvers are impractical. Future work will focus on enhancing model precision through hybrid learning strategies that incorporate labeled data, potentially enabling real-time predictive modeling for field applications. Full article

This study examines the effect of smooth and humped flow channels on the recovery of industrial magnetic seeds in a drum magnetic separator. The results demonstrate that under varying feeding slurry quantities and drum rotational speeds, the humped channel consistently achieves higher recovery rates compared with the smooth channel, with an improvement of up to 3%. Scanning electron microscopy and vibrating sample magnetometry analyses of the samples reveal the presence of a small amount of impurities (predominantly consisting of elements, such as Al, Si, and Ti) in the industrial magnetite magnetic particles. These impurities exhibit lower magnetization, leading to reduced capture efficiency in the conventional smooth-channel drum magnetic separator. Simulations of the magnetic field, flow field, and particle trajectory indicate that the magnetic field force at the bottom of the smooth channel is only 0.6 kg²/(m·s⁴·A²), i.e., approximately 18 times lower than that at the roller surface. The incorporation of a humped channel shifts the impure magnetic seeds from a region with low magnetic field force to a region with higher magnetic field force, significantly enhancing the capture efficiency of the impure magnetic seeds. Full article

This study investigates cement–bentonite slurries with hydration accelerators for borehole backfilling applications in infrastructure reconstruction projects. Two formulations with different accelerator dosages (5 and 10 kg/m³) were evaluated through combined experimental testing and Moving Particle Semi-implicit (MPS) numerical modeling to optimize material performance. The research focuses on time-dependent rheological evolution and its impact on construction performance, particularly bleeding resistance and workability retention. Experimental flow tests revealed that both formulations maintained similar initial flowability (240–245 mm spread diameter), but the higher accelerator dosage resulted in 33% flow reduction after 60 min compared to 12% for the lower dosage. Bleeding tests demonstrated significant improvement in phase stability, with bleeding rates reduced from 2.5% to 1.5% when accelerator content was doubled. The MPS framework successfully reproduced experimental behavior with prediction accuracies within 3%, enabling quantitative analysis of time-dependent rheological parameters through inverse analysis. The study revealed that yield stress evolution governs both flow characteristics and bleeding resistance, with increases several hundred percent over 60 min while plastic viscosity remained relatively constant. Critically, simulations incorporating time-dependent viscosity changes accurately predicted bleeding behavior, while constant-viscosity models overestimated bleeding rates by 60–130%. The higher accelerator formulation (10 kg/m³) provided an optimal balance between initial workability and long-term stability for typical borehole backfilling operations. This integrated experimental–numerical approach provides practical insights for material optimization in infrastructure reconstruction projects, particularly relevant for aging infrastructure requiring proper foundation treatment. The methodology offers construction practitioners a robust framework for material selection and performance prediction in borehole backfilling applications, contributing to improved construction quality and reduced project risks. Full article

The phase-change solidification plugging material (PSPM), a novel type of plugging material for severe fluid loss in demanding formations, necessitates performance enhancement and deeper insight into its hydration mechanism. In this paper, with a foundational formula comprising a nucleating agent (S1), activator (M1), and deionized water, a comprehensive investigation was conducted. This involved basic performance testing, including fluidity, setting or thickening time, hydration heat analysis, SEM and XRD for hydration products, and conduction of kinetics model. The focus was on analyzing the effects of three additives on system properties, hydration process, and hydration products, leading to the inference of the hydration mechanism of PSPM. It was found that the structure additives (SA) and flow pattern regulator (6301) did not partake in the hydration reaction, focusing instead on enhancing structure strength and maintaining slurry stability, respectively. Conversely, the phase regulator (BA) actively engaged in the hydration process, transitioning the system from the KG-N-D to the KG-D model, thereby extending the thickening time without altering the final hydration products. The morphology and composition of the products confirmed that SI and M1 dissolve in the aqueous solution and progressively form Mg(OH)₂ and MgSO₄·zMg(OH)₂·xH₂O. The slurry gradually solidifies, ultimately resulting in the formation of a high-strength consolidated body, thereby achieving the objective of lost circulation control. Full article