Search Results (606)

This study presents an eccentric pipe separator (EPS) designed according to the shallow pool principle and Stokes’ law as a compact alternative to conventional gravitational tank separators for offshore platforms. To investigate the internal oil–water flow characteristics and separation performance of the EPS, both field experiments with crude oil on an offshore platform and computational fluid dynamics (CFD) simulations were conducted, guided by dimensional analysis. Crude oil volume fractions were measured using a Coriolis mass flow meter and the fluorescence method. The CFD analysis employed an Eulerian multiphase model coupled with the renormalization group (RNG) k-ε turbulence model, validated against experimental data. Under the operating conditions examined, the separated water contained less than 50 mg/L of oil, while the separated crude oil achieved a purity of 98%, corresponding to a separation efficiency of 97%. The split ratios between the oil and upper outlets were found to strongly influence the phase distribution, velocity field, and pressure distribution within the EPS. Higher split ratios caused crude oil to accumulate in the upper core region and annulus. Maximum separation efficiency occurred when the combined split ratio of the upper and oil outlets matched the inlet oil volume fraction. Excessively high split ratios led to excessive water entrainment in the separated oil, whereas excessively low ratios resulted in excessive oil entrainment in the separated water. Crude oil density and inlet velocity exhibited an inverse relationship with separation efficiency; as these parameters increased, reduced droplet settling diminished optimal efficiency. In contrast, crude oil viscosity showed a positive correlation with the pressure drop between the inlet and oil outlet. Overall, the EPS demonstrates a viable, space-efficient alternative for oil–water separation in offshore oil production. Full article

Hydrogen-based direct reduction (H-DR) represents an environmentally benign and energy-efficient alternative in ironmaking that has significant industrial potential. This study reviews the current status of H-DR shaft furnaces and accompanying hydrogen-rich reforming technologies (steam and autothermal reforming), assessing the three dominant numerical frameworks used to analyze these processes: (i) porous medium continuum models, (ii) the Eulerian two-fluid model (TFMs), and (iii) coupled computational fluid dynamics (CFD)–discrete element method (DEM) models. The respective trade-offs in terms of computational cost and model accuracy are critically compared. Recent progress is evaluated from an engineering standpoint in four key areas: optimization of the pellet bed structure and gas distribution, thermal control of the reduction zone, sensitivity analysis of operating parameters, and industrial-scale model validation. Current limitations in predictive accuracy, computational efficiency, and plant-level transferability are identified, and possible mitigation strategies are discussed. Looking forward, high-fidelity multi-physics coupling, advanced mesoscale descriptions, AI-accelerated surrogate models, and rigorous uncertainty quantification can facilitate effective scalable and intelligent application of hydrogen-based shaft furnace simulations. Full article

This study numerically investigates pavement damage caused by explosions in buried leaking natural gas pipelines using a coupled Lagrangian–Eulerian (CLE) framework in LS-DYNA. The gas phase is described by a Jones–Wilkins–Lee-based equation of state, while soil and pavement are modeled using a pressure-dependent soil model and the Riedel–Hiermaier–Thoma concrete model with strain-based erosion, respectively. The approach is validated against benchmark underground explosion tests in sand and blast tests on reinforced concrete slabs, demonstrating accurate prediction of pressure histories, ejecta evolution, and crater or damage patterns. Parametric analyses are then conducted for different leaked gas masses and pipeline burial depths to quantify shock transmission, soil heave, pavement deflection, and damage evolution. The results indicate that the dynamic response of the pavement structure is most pronounced directly above the detonation point and intensifies significantly with increasing total leaked gas mass. For a total leaked gas mass of 36 kg, the maximum vertical deflection, the peak kinetic energy, and the peak pressure at the bottom interface at this location reach 148.46 mm, 14.64 kJ, and 10.82 MPa, respectively. Moreover, a deflection-based index is introduced to classify pavement response into slight (<20 mm), moderate (20–40 mm), severe (40–80 mm), and collapse (>80 mm) states, and empirical curves are derived to predict damage level from leakage mass and burial depth. Finally, the effectiveness of carbon fiber reinforced polymer (CFRP) strengthening schemes is assessed, showing that top and bottom surface reinforcement with a total CFRP thickness of 2.67 mm could reduce vertical deflection by up to 37.93% and significantly mitigates longitudinal cracking. The results provide a rational basis for safety assessment and blast resistant design of pavement structures above buried gas pipelines. Full article

This work describes an innovative three-dimensional model of a proton exchange membrane electrolyzer. For the first time, a multi-phase model has captured segregated channel flow together with multiphase flow in a porous medium, as well as heat transfer and phase change employing an Eulerian multiphase model. The novel electrolyzer design investigated employs a symmetrical, interdigitated flow field to facilitate even water distribution. In the current case, a hot spot is predicted with a temperature increase of 7 °C at a current density of 1.0 A/cm². The flow field plates are horizontally oriented, and it is shown that gravity plays an important role in the electrolyzer design and orientation. A parametric study shows, for the first time, the effect of operating a PEM electrolyzer at sub-ambient anode pressure to favorably adjust the concentration ratio between water vapor and oxygen in the anode compartment. This ratio is increased by a factor of 5.6 when the pressure is decreased from one bar to 500 mbar. Full article

With the growing requirements for multi-particle process simulation, improving computational accuracy, efficiency, and scalability has become a critical challenge. This study generally focused on comprehensive analyses of existing numerical methods for simulating particle–substrate interactions in gas–thermal spraying (including gas–dynamic spraying processes), covering both single-particle and multi-particle models to develop practical recommendations for the optimization of modern coating spraying processes. First of all, this paper systematically analyzes the key limitations of current approaches, including their inability to handle high deformations effectively or high computational complexity and their insufficient accuracy in dynamic scenarios. A comparative evaluation of four numerical methods (Lagrangian, Arbitrary Lagrangian–Eulerian (ALE), Coupled Eulerian–Lagrangian (CEL), and Smoothed Particle Hydrodynamics (SPH)) revealed their strengths and weaknesses in modeling of real gas–thermal spraying processes. Furthermore, this study identifies the limitations of the widely used Johnson–Cook (JC) constitutive model under extreme conditions. The authors considered the Zerilli–Armstrong (ZA), Mechanical Threshold Stress (MTS), and Preston–Tonks–Wallace (PTW) models as more realistic alternatives to the Jonson–Cook model. Finally, comparative analyses of theoretical and realistic deformation and defect-generation processes in gas–thermal coatings emphasize the critical need for fundamental changes in the simulation strategy for modern gas–thermal spraying processes. Full article

This study proposes a model for a wet string grid dust removal system based on gas–droplet–particle turbulent Eulerian–Lagrangian simulation, providing in-depth insights into the dust removal mechanism of droplet groups and its impact on dust collection efficiency. Through numerical simulations and theoretical derivation, we systematically introduce the mathematical expression of the droplet group dust removal efficiency and validate its applicability in wet string grid dust removal processes. The study reveals that the dust removal efficiency of the wet string grid system is influenced by multiple factors, including airflow velocity, droplet distribution, and the interaction between droplets and dust particles. By adjusting spray volume, wind speed, and the geometric parameters of the water mist zone, the dust removal process was optimized. The results show that increasing the wind speed enhances dust removal efficiency, but excessive wind speed reduces the dust capture efficiency of droplets. Additionally, based on simulation results of the flow field, the study identifies key factors influencing the dust removal efficiency of droplet groups and provides valuable insights for optimizing wet string grid dust removal systems in practical engineering. Full article

Branched horizontal wells are widely applied in oil and gas development. However, their complex structures make cuttings transport and deposition problems more pronounced. In this study, a three-dimensional branched wellbore model was established based on an intelligent drilling and completion simulation system. A computational fluid dynamics (CFD) approach, incorporating the Eulerian–Eulerian two-fluid model and the kinetic theory of granular flow, was employed to investigate the effects of wellbore diameter, eccentricity, curvature, flow rate, and rheological parameters on cuttings transport behavior. Results from the steady-state simulations indicate that increasing the wellbore diameter and eccentricity intensifies cuttings deposition at the connection section, with the lower-region concentration rising significantly as the eccentricity increases from 0% to 60%. A larger curvature enhances local flow disturbance but reduces the overall cuttings transport efficiency. Increasing the flow rate improves hole cleaning but may promote cuttings accumulation near the bottom of the main wellbore. As the flow behavior index increases from 0.4 to 0.8, the average cuttings concentration rises from 0.0996 to 0.1008, and the pressure drop increases from 1,010,894 Pa to 1,042,880 Pa, indicating improved transport capacity but higher energy consumption. Experimental results are consistent with the numerical simulation trends, confirming the model’s reliability. This study provides both theoretical and experimental support for optimizing complex wellbore structures and drilling fluid parameters. Full article

Municipal solid waste (MSW) composition and properties play a critical role in determining the efficiency and environmental impact of waste incineration processes. However, the effects of moisture variation in MSW on combustion performance in full-scale grate systems remain insufficiently understood. To reveal how the moisture variation in municipal solid waste (MSW) properties affects the combustion process in full-scale grate systems, a 50 t/d mechanical grate incinerator was modeled. The influence of MSW inlet moisture content (42.85%, 35.71%, and 28.57%) was investigated. When the moisture content is 35.71%, the horizontal and vertical temperature gradient of the incinerator was least pronounced, and the high-temperature zone in the incinerator would not be locally concentrated. The moderate ignition position could reduce the corrosion of the front and rear arches of the grate incinerator. In the combustion process of three moisture contents, the complete evaporation positions were located at X = 4.23 m in the combustion section, X = 3.15 m in the drying section and X = 2.63 m in the drying section, the corresponding ignition points were X = 6 m, X = 4.47 m, and X = 3.74 m in the combustion section, respectively. After the moisture content was reduced to 35.71% and 28.57%, the drying process was advanced by 25.5% and 37.8%, respectively; the ignition points were advanced by 25.5% and 37.7%, respectively. It is recommended that the moisture content of MSW be maintained within the range of 33.8% to 41.6% under practical operating conditions. With the decrease in the moisture content of the MSW, the O₂ content at the incinerator outlet decreased; the CO₂ content increased. The findings offer quantitative guidance on feed pre-treatment for MSW incineration plants. Full article

A touch-off explosion on concrete slabs is considered one of the simplest yet most destructive forms of adversarial loading on building elements. It causes far greater damage than explosions occurring at a distance. The impact is usually concentrated in a small area, leading to surface cratering, scabbing of concrete, and even tearing or rupture of the reinforcement. Studies available on the behavior of reinforced concrete (RC) slabs under touch-off (contact) and standoff explosions commonly indicate that the maximum damage occurs when the blast is applied to the center of the slab. This observation raises an important question about how the position of an explosive charge, especially relative to the free edge of the slab, affects the overall damage pattern in slabs supported on only two sides with clamped supports. This study uses a modeling strategy combining Eulerian and Lagrangian domains using the finite element tools of Abaqus Explicit v2020 to examine the behavior of a square slab supported on two sides with clamped ends subjected to blast loads at different positions, ranging from the center to the free edge and beyond, under touch-off explosion conditions. The behavior of concrete was captured using the Concrete Damage Plasticity model, while the reinforcement was represented with the Johnson–Cook model. Effects of strain rate were included by applying calibrated dynamic increase factors. The developed numerical model is validated first with experimental data available in the published literature for the case where the explosive charge is positioned at the slab’s center, showing a very close agreement with the reported results. Along with the central blast position, five additional cases were considered for further investigation as they have not been investigated in the existing literature and were found to be worthy of study. The selected locations of the explosive charge included an intermediate zone (between the slab center and free edge), an in-slab region (partly embedded at the free edge), a partial edge (partially outside the slab), an external edge (fully outside the free edge), and an offset position (250 mm beyond the free edge along the central axis). Results indicated a noticeable transition in damage patterns as the detonation point shifted from the slab’s center toward and beyond the free edge. The failure mode changed from a balanced perforation under confined conditions to an asymmetric response near the free edge, dominated by weaker surface coupling but more pronounced tensile cracking and bottom-face perforation. The reinforcement experienced significantly varying tensile and compressive stresses depending on blast position, with the highest tensile demand occurring near free-edge detonations due to intensified local bending and uneven shock reflection. Full article

Current research on tower crane control lacks high-fidelity models and fails to account for the coupling effects between the tower crane structure and the hoisting and luffing systems. A new dynamic analysis platform based on the flexible multibody system theory is proposed in this investigation for the tower crane which contains a large-scale steel structure and hoisting mechanisms undergoing large displacements and large deformations. The Arbitrary Lagrangian–Eulerian–Absolute Nodal Coordinate Formulation (ALE–ANCF) cable element was employed to model the varying length of the steel rope in the hoisting mechanisms. Nonlinear kinetic equations were used to describe the motion of a luffing trolley. The solving strategy of the system’s dynamical equations are presented. Two different trajectories were tested. Simulation results demonstrate the feasibility and rationality of the proposed dynamic analysis platform. The primary conclusion is that this platform serves as a reliable and high-fidelity testbed for developing and evaluating advanced control algorithms under realistic dynamic conditions, thereby providing a dependable tool for both research and engineering applications. Full article

Air flotation separation technology has emerged as one of the core techniques for oily wastewater treatment in oilfields, owing to its advantages of high throughput, high separation efficiency, and short retention time. Originally applied in mineral processing, this technology was first introduced to oilfield produced water treatment by Shell in 1960. With the optimization of microbubble generators, advances in microbubble generation technology—characterized by small size, high stability, and uniformity—have further expanded its applications across various wastewater treatment scenarios. To optimize the separation performance of a horizontal compact closed-loop cyclonic air flotation unit, this study employs CFD numerical simulation to investigate two key aspects: First, for the flotation zone, the effects of structural parameters (deflector height, inclination angle) and operational parameters (gas–oil ratio, bubble size, inlet velocity) on flow patterns and gas distribution were systematically examined. Device performance was evaluated using metrics such as gas–oil ratio distribution curves and flow field characteristics, enabling the identification of operating conditions for stratified flow formation and the determination of optimal deflector structural parameters. Second, based on the Eulerian multiphase flow model and RSM turbulence model, a numerical simulation model for the oil–gas–water three-phase flow field was established. The influences of key parameters (bubble size, throughput, gas–oil ratio) on oil–water separation efficiency were investigated, and the optimal operating conditions for the unit were determined by integrating oil-phase/gas-phase distribution characteristics with oil removal rate data. This research provides theoretical support for the structural optimization and engineering application of horizontal compact closed-loop cyclonic flotation units. Full article

The flow field evolution in the first turn of the spiral concentrator is decisive for the separation efficiency of solid particles. A laboratory-scale Φ300 mm spiral concentrator was employed as the study subject. The fluid phase was simulated using the RNG k-ε (Renormalization Group) turbulence model and the VOF (Volume of Fluid) multiphase model, while the particles were calculated with an Eulerian multi-fluid VOF model that incorporates the Bagnold effect. The influence of the cross-sectional curve equation on the evolution of flow field parameters in the first turn and on the separation behavior of hematite and quartz particles was systematically investigated. The results indicated that the evolution characteristics of fluid parameters, such as the depth of flow film, the tangential velocity of surface flow, the velocity of secondary circulation, and radial flux, were similar. All parameters were observed to undergo an initial decrease or increase, eventually stabilizing as the longitudinal travel progressed. A negative correlation was identified between the index of the cross-sectional curve equation and both the depth of flow film and the tangential velocity of surface flow in the inner half of the trough, whereas an inverse relationship was noted in the outer half. With an increase in the index of the cross-sectional curve equation, the outward circulation velocity in the initial stage and its radial flux in the outer zone were enhanced, while the fluctuations in the evolution of local fluid parameters were suppressed, with more active fluid radial migration observed at the indices of the cross-sectional curve equation of 2.5 and 3. As the flow field evolved, axial separation between hematite and quartz particles was progressively achieved by gravity due to their density difference. In the middle and inner-outer zones, the migration directions of hematite and quartz were observed to become opposite in the later stage of evolution, while the difference in their migration magnitudes was also found to be widened. With an increase in the index of the cross-sectional curve equation, the disparity in the axial separation and movement between hematite and quartz was enhanced, albeit with a diminishing rate of increase. The maximum separation efficiency between hematite and quartz particles was significantly improved with increased longitudinal travel, reaching over 60% by the end of the first turn; higher indices were determined to be more favorable for achieving this performance. Based on the previous research, the variation in separation indices in the third turn was investigated under both independent adjustment of the index of the cross-sectional curve equation and its combined adjustment with the downward bevel angle. Relatively high and stable separation performance was achieved with the indices of the cross-sectional curve equation of 2.5 and 3, where a maximum separation efficiency of 82.02% was obtained, thereby validating the high efficiency and suitability of the selected spiral concentrator profile. This research elucidated the decisive role of the flow field evolution through the first turn in particle separation behavior from the perspective of quantitative description of hydrodynamic parameters, providing beneficial references for the cross-sectional structure design of spirals and the prediction of the separation index of specific feed. Full article

Flow regimes of vertical upflow for slightly cohesive Geldart A powders at high solids mass flux ($G_s$$\gtrsim$ 500 kg/m²s) are not fully resolved. In particular, Dense Suspension Upflow (DSU) as a distinct flow regime and its transition boundaries are not broadly accepted. Furthermore, the locus of the pressure gradient minimum, which is the broadly accepted dense–dilute transition at low $G_s,$ requires validation at high $G_s$. In our recent work, by adapting the phase map of Wirth and by Eulerian modeling, DSU was defined as a distinct flow regime with gross upflow of solids and with granular temperature at the wall greater than that in the bulk. This study has further validated the definition of DSU and its transition boundaries by extending the modeling to areas not fully explored in the earlier work. Furthermore, this study has identified (a) the possibility of a phase of DSU between fast fluidization and turbulent regime at all $G_s$; and (b) the need to review the suitability of the locus of the pressure gradient minimum as the dense–dilute transition at high $G_s$. Additionally, our work has demonstrated (a) a new provisional correlation that the upper transport velocity for Geldart A powders is significantly greater than hitherto predicted; and (b) the slip velocity in the transport regimes increases with $G_s$ to peak within fast fluidization and falls thereafter to attain low multiples of the terminal settling velocity within DSU. Full article

This study investigates the effects of spume droplets on coherent vortical structures (CVSs) in turbulent airflow over a wavy water surface, focusing on the role of wave steepness and droplet injection velocity in modulating these interactions. Direct numerical simulations are performed using a droplet-laden Couette turbulent airflow over progressive surface waves as an idealized model. A Eulerian-Lagrangian approach is employed, considering low- and high-steepness wave conditions ($ak =0.1$ and $0.2$, where $a$ is wave amplitude and $k$ is wavenumber) and two droplet injection velocities (surface and airflow velocities near wave crest). Results from droplet-free simulations reveal strong phase dependence in CVS formation, with forward and reversed horseshoe vortices near wave troughs and quasi-streamwise vortices aligning along the windward surface. Droplets injected at the surface velocity remain near wave crests, where CVS formation is weak, leading to minimal interaction. In contrast, droplets injected at the airflow velocity disperse broadly, increasing the likelihood of interactions with CVSs. For low-steepness waves, these droplets stay within the surface layer, attenuating CVSs and suppressing ejection and sweep events. However, as wave steepness increases, more droplets escape the near-surface layer, reducing their influence on CVSs. Full article

Wet milling of aluminum alloys involves complex interactions among thermal, fluid, and mechanical fields that strongly affect cutting temperature, stress distribution, and surface integrity. To achieve reproducible and physics-based predictions of these coupled phenomena, this study develops a three-dimensional thermo–fluid–solid-coupled Eulerian–Lagrangian (CEL) framework for the wet milling of Al6061. The model system in this study evaluated the effects of milling cutter feed rate and spindle speed, feed per tooth of the milling cutter, axial cutting depth, and coolant flow rate on equivalent stress and peak milling temperature., as well as their correlation with surface roughness metrics (Ra, Sa). Simulation results reveal that higher feed rates significantly raise T_peak (+12.9%) while reducing σ_eq (−22.7%) and deteriorating surface quality (Ra +104.2%, Sa +29.9%). Increasing spindle speed lowers both T_peak (−2.2%) and σ_eq (−8.5%) and improves surface finish (Ra −39.3%, Sa −16.6%). A greater depth of cut amplifies mechanical and thermal loads, increasing T_peak (+10.3%) and σ_eq (+17%). Enhanced coolant flow reduces T_peak (−23.5%) and σ_eq (−6.1%) and markedly improves surface quality (Ra −88.8%, Sa −51.3%). Research findings indicate that coolant coverage is the dominant factor determining surface integrity. Although experimental data for T_peak and σeq were not directly validated, this framework clearly articulates modeling assumptions, quantifies parameter sensitivities, and provides a reproducible methodology for future experimental-numerical verification. Full article