Search Results (235)

This study utilizes a large-scale numerical simulation model to investigate the hydrodynamic behavior and particle transport characteristics of gas–liquid–solid three-phase flow in vertical wellbores featuring multi-source confluence and curved geometries. Simulation results indicate that increasing flow velocity shifts the dominant control mechanism from surface tension to inertial forces, transitioning the flow pattern from slug flow to churn flow. In curved pipe sections, centrifugal phase separation and geometric shielding effects cause significant flow asymmetry and maintain large bubble stability at the inner wall. Additionally, the multi-inlet structure induces shear rate gradients that result in the spatial coexistence of two distinct bubble scales. Furthermore, localized gas concentrations exceeding 70% at the upper inlet can trigger severe gas-locking phenomena and intense pressure pulsations. Full article

The mixing valve is a key component of an ultra-high-pressure premixed abrasive waterjet system, in which the abrasive–water mixing uniformity plays a decisive role in determining the erosion and cutting performance of the jet. The geometric parameters of the mixing chamber inside the valve are therefore critical factors affecting this uniformity. In this study, the liquid–solid two-phase flow within the mixing chamber was numerically investigated using the Eulerian k–ε turbulence model coupled with the Fluent–Rocky DEM approach. Single-factor simulations were first conducted to identify the effective ranges of key structural parameters influencing the mixing performance. Subsequently, a response surface model was established to describe the relationship between the mixing efficiency (ME) and four critical chamber parameters, namely the throat diameter (TD), throat length (TL), abrasive inlet pipe diameter (AD), and the distance between the throat exit and the abrasive inlet pipe center (TE). Based on this model, the optimal structural parameters of the mixing chamber were determined. The results indicate that when TD = 4 mm, TL = 12 mm, AD = 10 mm, and TE = 7 mm, the simulated ME reaches 34.40% ± 0.49%, which is in close agreement with the predicted value of 34.57%. Experimental validation conducted on a premixed abrasive waterjet test rig shows that the mean absolute relative error between the simulated and measured ME values is 7.54%, which is below the 10% threshold, confirming the reliability and accuracy of the numerical model. Full article

Two-stage anaerobic digestion systems are extensively researched for enhancing process stability and phase separation when processing complex organic materials. Scaling from laboratory setups to pilot plants necessitates engineering modifications to ensure operational feasibility. In this study, a laboratory-scale system comprising a 100 L horizontal CSTR and a packed-bed reactor was scaled up 100-fold. The design separates solid and liquid retention times, with fibers retained in the first stage while liquids and volatile fatty acids flow into the second. Fiber retention in the lab was achieved using a 100 µm sieve dividing the CSTR into two chambers, allowing prolonged lignocellulosic degradation. During scale-up, a filtration and recirculation system was introduced, able to return the fibers to the first reactor through a 1000 µm edge-gap filter, which separates liquids for the second reactor and recycles undegraded fibers. An economic analysis indicated a scale-up exponent of 0.396, indicating that unit costs decrease with plant size and demonstrating economies of scale. Laboratory-based mass balance estimates biogas production at approximately 16.3 m³ daily at the pilot scale, equivalent to 90 kWh. The modular system aims to be transferred to small farms, promoting cost-effective biogas from manure and local residues to support decentralized renewable energy in agriculture. Full article

Double-wall drill pipe reverse circulation drilling is expected to alleviate cutting-transport difficulties and the high risk of lost circulation during the shallow-section drilling of ultra-deep wells. Based on wellbore hydraulics theory and a transient solid–liquid two-phase flow model in the wellbore, considering the flow path transition effect at the reverse circulation converter near the bit, a corrected pressure loss method for the inner pipe accounting for cuttings influence is proposed, and a correlation for calculating the converter pressure loss is derived. A wellbore pressure calculation model for reverse circulation drilling using a double-wall drill pipe is then established. Furthermore, the influencing factors are investigated through sensitivity analysis, and a pump pressure selection chart is developed. Field-case calculations indicate that, under identical operating conditions, the bottomhole pressure in double-wall drill pipe reverse circulation drilling is reduced by approximately 6.31 MPa compared with conventional drilling. For shallow sections (well depth of about 1200 m) under flow rates of 20–40 L/s and drilling-fluid densities of 1200–1400 kg/m³, the maximum total circulating wellbore pressure loss, after incorporating surface flowline pressure losses, is approximately 10.91 MPa. In this case, a single pump can satisfy the circulation requirement, demonstrating the advantages of simplified equipment configuration and improved field adaptability for shallow-section operations. The proposed model and charts can provide a reference for parameter optimization and pressure-control design in double-wall drill pipe reverse circulation drilling. Full article

This study utilizes computational fluid dynamics (CFD), numerical simulation of particle separation characteristics enhanced by synergistic extraction–shearing is performed, and the two-phase flow in a liquid–solid stirred tank is simulated using the Eulerian–Eulerian two-fluid model and the standard $k-\epsilon$ model. The effects of impeller speed, the hole arrangement pattern of the annular shroud, and the hole area on the multiphase fluid dynamics behavior and stirring power inside the tank are systematically studied. The results show that stirring speed is a key operating parameter affecting turbulence intensity and particle mixing uniformity. When the stirring speed increases from 2000 r/min to 4000 r/min, the overall tank turbulence increases significantly, but the stirring power increases from 4.69 kW to 36.57 kW. The annular cover at the bottom is arranged with vertical openings, which enables full energy transfer within the tank and effectively enhances the turbulence intensity in the middle and lower sections of the flow field; the horizontal opening form is more conducive to the radial diffusion of particles in the middle layer. Reducing the hole area by half increases the fluid jet velocity and local shear stress, effectively improving particle distribution uniformity, while the stirring power decreases by 43.75%, thereby achieving the collaborative optimization of mixing efficiency and energy consumption. Full article

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

This study systematically investigates the gas–liquid phase transition heat transfer characteristics and volatilization loss behavior of magnetic liquid sealing devices under high-temperature and high-speed operating conditions. A magneto-thermal flow-coupled numerical model was established using ANSYS Maxwell (2025 R1) and Fluent (2025 R1) software to simulate and analyze the influence of rotational speed, solid content, and shaft diameter on the temperature distribution and gas-phase evolution of the magnetic liquid within the sealing gap. An experimental platform was also constructed for validation. The research indicates that increasing rotational speed significantly intensifies the vaporization of magnetic liquid, with bubbles migrating towards lower-concentration regions. The influence weight of rotational speed on phase transition is greater than that of shaft diameter. Under identical temperature fields, the phase transition interface morphology and the proportion of gas–liquid two-phase regions among magnetic liquids with different solid contents are highly similar. However, high-solid-content magnetic liquid can inhibit phase transition due to dense particle packing. Increasing shaft diameter notably expands the vaporization region, easily forming through-leakage channels. Full article

Erosive wear in pipe elbows subjected to liquid–solid two-phase flow is a major cause of material degradation and service failure in industrial piping systems. In this study, erosion characteristics of pipe elbows were investigated through erosion mapping experiments and numerical simulations. The effects of flow velocity and particle diameter on erosion location and intensity were analyzed. Erosion was found to be mainly concentrated on the outer wall of the elbow within the angular range of 10° to 90°, and both erosion intensity and affected area increased with increasing particle diameter and flow velocity. Dean vortices were shown to play an important role in particle transport and erosion distribution, especially for small particles. Inspired by the ribbed morphology of shells, a biomimetic elbow was further designed and evaluated through an orthogonal numerical study considering flow velocity, particle diameter, rib number, and rib diameter. The results indicate that the ribbed structure can effectively improve erosion resistance by altering particle trajectories, reducing particle impact probability, and dissipating kinetic energy through low-velocity rotating flow between adjacent ribs. This finding provides useful inspiration for addressing erosive wear problems in engineering applications. Full article

To elucidate the hydraulic transport characteristics of coarse-particle slurry in deep-sea mining vertical lifting pipelines and the governing effects of key operating parameters, a bidirectionally coupled CFD-DEM model was established, in which seawater was treated as the continuous phase and ore particles were treated as the discrete phase, while particle–fluid momentum exchange and particle–particle/particle–wall collisions were explicitly accounted for. The effects of inlet velocity, feed concentration, particle size, and particle shape on local particle concentration, local particle flow rate, and particle volume fraction distribution were systematically investigated. The results show that increasing the inlet velocity markedly reduces local particle concentration, increases the local particle flow rate, and promotes a faster transition of the solid–liquid two-phase flow toward a uniformly mixed state. Increasing the feed concentration enhances the conveying capacity, but simultaneously increases the risk of particle aggregation. The effect of particle size on local concentration is non-monotonic: the local concentration is relatively high at approximately 20 mm, whereas smaller particles exhibit better flow uniformity. The effect of particle shape is mainly manifested under low-velocity and high-concentration conditions, and gradually weakens with increasing inlet velocity. The present results provide a theoretical basis for parameter optimization of deep-sea mining vertical lifting systems. Full article

To address the imbalance between the shearing–mixing quality and energy efficiency of deepwater drilling mud mixers and breakthrough the limitations of existing independent single-objective analytical perspectives, the Eulerian solid–liquid two-phase numerical simulation was adopted in this study. Combined with a modified shear rate algorithm and a triple energy coupling analysis of shear rate, Lamb vortex energy and Enstrophy, the energy conversion and particle dispersion mechanisms inside the mixer under variable flow rates and solid concentrations were systematically investigated, and the performance differences between the first-generation and optimized mixers were clarified. Structural optimizations including an additional modular stator with a designed shear gap of 2 mm, improved blade profiles and shear angles to 14.2°, and miniaturized radial dimensions of the impeller and volute were implemented to achieve compact structural upgrading. The results demonstrate that high-energy regions are concentrated in the rotor–stator gap. After optimization, the peak shear rate increases from 12,010 s⁻¹ to 17,092 s⁻¹, representing a 42.3% enhancement. The peak Lamb vortex energy and the mean Enstrophy rise by 8.6% and 18.9%, respectively. Shear rate correlates weakly positively with Lamb vortex energy and strongly negatively with Enstrophy, revealing vortex sensitivity to flow velocity and tight coupling of viscous dissipation to particle concentration. The outlet coefficient of variation C_v decreases by 59.6%. Higher flow rates strengthen the coupling of shear and vortex energy, and higher solid concentrations weaken stator shear performance. The optimized mixer achieves synergistic improvements in shear efficiency and mixing quality, with over 50% enhancement in mud dispersion stability and more than 15%. Full article

The transport mechanism of non-spherical particles in complex pipelines, such as right-angle elbows, remains insufficiently understood, posing challenges to the efficiency optimization of industrial systems like deep-sea mining. This study investigates the fundamental mechanisms governing the upward transport of 1–15 mm non-spherical particles in a 100 mm right-angle bend by integrating Particle Image Velocimetry (PIV) experiments with coupled computational fluid dynamics and discrete element method (CFD-DEM) simulations. We systematically quantify the effects of key factors—flow velocity, particle size distribution, and shape factor (ranging from 0.4 to 1)—on flow asymmetry, particle dynamics, and transport efficiency. The results reveal a pronounced flow asymmetry, where the outer-side peak velocity is approximately twice that of the inner side, accompanied by a persistent separation vortex. Crucially, transport efficiency is governed by particle interactions: wide-grading blends achieve up to 12% higher conveying speed than narrow fractions at high flow rates. While spherical particles (shape factor, SF = 1) attain the highest axial velocity, particles with SF ≥ 0.8 are identified as optimal, maintaining moderate rotation, concentrating in the central high-speed zone, and thereby combining high transport velocity with minimal wall contact. These findings elucidate the underlying particle–fluid interactions in bends and provide a quantitative basis for optimizing particle morphology in industrial hydraulic transport systems. Full article

The current state and prospects of microreactor synthesis of functional materials in single- and two-phase flows with a liquid continuous phase are analyzed. Microreactors allow fine control over the size, composition, structure, and properties of synthesized particles in co-precipitation processes. The results obtained by various teams provide grounds to expect fairly extensive capabilities for controlling the processes of nucleation and particle growth in microreactors—by controlling the pH, reagent concentrations, micromixing quality, and residence time in each of the reactor zones—in the nucleation growth zones. The advantages of microreactor synthesis have been demonstrated with a high quality of micromixing in a volume of 0.2–0.5 mL, which ensures the production of nanoparticles without impurities, a stoichiometric ratio of atoms in the product, and limitation of agglomerate growth due to a short residence time (in the order of several milliseconds). The transition to an industrial scale is very easy due to the fairly high productivity of a single microreactor (up to 10 m³/day for suspension, up to 200–300 kg/day for solid phase). Intensive mixing in microreactors with a diameter of 2–4 mm or less, due to Taylor vortices, contributed to the use of two-phase microreactors for the synthesis of both organic and inorganic substances. Full article

Semi-open impeller sewage pumps are widely used for transporting solid-laden fluids due to their anti-clogging properties. However, unlike extensive research on clear water conditions, the specific mechanisms governing pressure instabilities under solid–liquid two-phase flows remain underexplored. This study investigates the unsteady flow field and pulsation characteristics of a Model 80WQ4QG pump using unsteady CFD simulations based on the Standard k−ϵ turbulence model and the Eulerian–Eulerian multiphase model. The effects of flow rate, particle size, and volume fraction were systematically analyzed. Results indicate that the blade-passing frequency (95 Hz) dominates the pressure spectra, with the volute tongue and impeller outlet identified as the most sensitive regions. While increased flow rates weaken fluctuations at the volute tongue, the presence of solid particles significantly amplifies them. Specifically, compared to single-phase flow, the pulsation amplitudes at the volute tongue increased by 68.15% with a 3.0 mm particle size and by 97.73% at a 20% volume fraction. Physically, this amplification is attributed to the intensified momentum exchange between phases and the enhanced turbulent flow disturbances induced by particle inertia at the rotor–stator interface. These findings clarify the particle-induced flow instability mechanisms, offering theoretical guidelines for optimizing pump durability in multiphase environments. Full article

During liquid drainage from intermediate vessels in various industrial processes such as continuous steel casting, aircraft fuel supply, and chemical separation, free-surface vortices commonly occur. The formation and evolution of these vortices not only entrain surface slag and gas, but also lead to deterioration of downstream product quality and abnormal equipment operation. The vortex evolution process exhibits notable three-dimensional unsteadiness, multi-scale turbulence, and dynamic gas–liquid interfacial changes, accompanied by strong coupling effects between temperature gradients and flow field structures. Traditional macroscopic numerical models show clear limitations in accurately capturing these complex physical mechanisms. To address these challenges, this study developed a mesoscopic numerical model for gas-liquid two-phase vortex flow based on the lattice Boltzmann method. The model systematically reveals the dynamic behavior during vortex evolution and the multi-field coupling mechanism with the temperature field while providing an in-depth analysis of how initial perturbation velocity regulates vortex intensity and stability. The results indicate that vortex evolution begins near the bottom drain outlet, with the tangential velocity distribution conforming to the theoretical Rankine vortex model. The vortex core velocity during the critical penetration stage is significantly higher than that during the initial depression stage. An increase in the initial perturbation velocity not only enhances vortex intensity and induces low-frequency oscillations of the vortex core but also markedly promotes the global convective heat transfer process. With regard to the temperature field, an increase in fluid temperature reduces the viscosity coefficient, thereby weakening viscous dissipation effects, which accelerates vortex development and prolongs drainage time. Meanwhile, the vortex structure—through the induction of Taylor vortices and a spiral pumping effect—drives shear mixing and radial thermal diffusion between fluid regions at different temperatures, leading to dynamic reconstruction and homogenization of the temperature field. The outcomes of this study not only provide a solid theoretical foundation for understanding the generation, evolution, and heat transfer mechanisms of vortices under industrial thermal conditions, but also offer clear engineering guidance for practical production-enabling optimized operational parameters to suppress vortices and enhance drainage efficiency. Full article

To investigate the influence of particle characteristics on wear in slurry pump flow-through components, this study established a computational fluid dynamics-discrete element method (CFD-DEM) coupled with the Archard wear model for numerical simulation of solid-liquid two-phase flow characteristics and wear mechanisms within the pump. Focusing on the correlation between wear contour distribution and particle collision frequency, the study systematically analyzed the influence mechanisms of particle concentration, size distribution, and shape on wear patterns within the pump. The reliability of the coupled model was validated through external characteristic tests. Results indicate that wear severity on both the impeller and volute increases significantly with rising particle concentration, while wall particle collision frequency exhibits a positive correlation with concentration. Particles of 1.5 mm diameter cause the most severe localized wear on the impeller, whereas the presence of mixed particles partially mitigates the wear effect of larger particles. Both total and localized wear on the volute peak at a particle diameter of 1 mm. Low-sphericity particles intensified overall wear on both the impeller and volute; while high-sphericity particles reduced overall wear, they induced more severe localized wear on the impeller. Volute localized wear was most pronounced at a sphericity of 0.84. This study elucidates the mechanism by which particle characteristics influence wear on slurry pump flow-through components, providing a theoretical basis for optimizing slurry pump design. Full article