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The current study aims to understand the particulate flow of the LD9 coal spiral concentrator using a multi-phase Computational Fluid Dynamics (CFD) model. The CFD model utilizes the Algebraic slip mixture model to simulate particulate flows. Initially, the volume of fluid (VOF) method and the Renormalization group k–ɛ turbulence model were adopted to track the water–air interface. The liquid depth and flow field predictions for varying flow rates were validated against the experimental literature data and found them in close agreement. Particulate flow simulations were then performed at low (0.3 and 3 wt%) and moderate (15 and 20 wt%) solids concentrations. Multiple particle-phase representing particles of poly sizes and multi-densities were simulated to study the particle segregation on the spiral trough surface. Predicted results showed close agreement with the experimental data. Further, this CFD model is used to study the change in pulp velocity, stream flow rates, and particle segregation at increasing solids concentration. For the same density particles, fines were mostly distributed in the middle and outer trough regions, whereas coarse particles were distributed in inner and central trough regions. Multi-phase flow predictions using the ASM model are promising to simulate particle dynamics at industrial feed solids concentration. The final implemented CFD model aids in designing the various spiral concentrators operating at moderate feed solids with different components. [ABSTRACT FROM AUTHOR]

The importance of this study is to investigate thoroughly the important design parameter "Erosion wear". Since erosion wear is a serious phenomenon in which material loss occurs due to the impact of the flow, research is going on experimentally and also computationally. Through the extensive study, various important parameters and flow characteristics were drawn and also discussed the importance given to that parameter which affects erosion wear. Thus, this analysis is useful for the researcher to take care of the important parameter either by the geometrical modification or adding the sacrificial element to the device or etc., to reduce the erosion wear which is taken care of and discussed in this paper. Various erosion test rigs developed by the researchers that can replicate the industrial environment were studied and the overview was given and also the author's point of view was briefly discussed in this paper. In addition to disseminating best practices and conducting an extensive review of the literature on experimental, computational, and mathematical investigations, the work's main accomplishments include the identification of certain research gaps and loose ends and the provision of future research directions was discussed. [ABSTRACT FROM AUTHOR]

Multiphase microfluidic has emerged as a powerful platform to produce novel materials with tailor-designed functionalities, as microfluidic fabrication provides precise controls over the size, component, and structure of resultant materials. Recently, functional materials with well-defined micro-/nanostructures fabricated by microfluidics find important applications as environmental and energy materials. This review first illustrated in detail how different structures or shapes of droplet and jet templates are formed by typical configurations of microfluidic channel networks and multiphase flow systems. Subsequently, recent progresses on several representative energy and environmental applications, such as water purification, water collecting and energy storage, were overviewed. Finally, it is envisioned that integrating microfluidics and other novel materials will play increasing important role in contributing environmental remediation and energy storage in near future.

Steam generator tube rupture (SGTR) accident is one of the accident scenarios that must be considered during the design and safety analysis process of lead-cooled fast reactors (LFR). Focused on this topic, numerous experiments and theoretical research have been conducted in recent decades, which could be generally categorized into two aspects: on the one hand, separation effect experiments and theoretical analysis focusing on the specific phenomena of lead-water interaction process; on the other hand, engineering test facilities and numerical simulations focusing on the overall process of LFR SGTR accident, mainly concentrated on the evolution of macro parameters such as system pressure and lead pool temperature during SGTR accident. In this paper, firstly, the basic mathematical and physical models of ACENA code was introduced; then the code was validated against the LBE-N2 two-phase flow experiment HESTIA-2, the KYILN-Ⅱ-S LBE-H2O interaction experiment and the analytical solution of the point-kinetic neutronic equations; after that the Eulerian multi-phase analysis code ACENA was applied to simulate the postulated unprotected SGTR process of European pool-type lead-cooled fast reactor ALFRED. Attention was paid to the simulated migration process of steam bubbles in the lead pool as well as the evolution of safety parameters such as maximum cladding temperature, fuel centerline temperature, relative nuclear power and reactor vessel pressure. Furthermore, the sensitivity of ruptured tube quantities, lead coolant circulation paths and neutron dynamics parameters on calculation results were analyzed. This paper’s study demonstrates that the Ishii-Chawla-Suzuki interfacial drag coefficient model could accurately predict the diffusion and migration characteristics of rising bubbles in circular/annular LBE flow channels when combined with the interfacial area concentration transport model proposed by Ishii et al; The simulation of KYLIN-Ⅱ-S experiment shows that ACENA code could reasonably reproduce phenomena such as system pressure fluctuations and temperature transients of liquid lead during the interaction process between LBE and water; the calculated results of ALFRED reactor’s key thermal-hydraulic parameters under hot full power condition by ACENA code are generally consistent with results obtained by internationally recognized one-dimensional system code TRACE/FRED, proving the reliability of ACENA code when applied to full reactor system level; The calculation of the hypothetical SGTR accident of the ALFRED reactor verifies the ACENA code’s capability of simulating the complex multi-component multi-phase flow, and the calculation results reveal that designing the primary coolant flow path rationally and reducing the number of ruptured pipes are of great significance to mitigating the potential consequences of LFR SGTR accidents. This work can provide reference for the safety analysis work of China’s pool-type lead-cooled fast reactors.

In this study, we present a successful application of the Computational Fluid Dynamics–Discrete Element Method (CFD–DEM) for simulating the complex phenomenon of multi-particle arch formation within high-concentration packed-bed environments. We investigate the roles of physical forces in this phenomenon, shedding light on aspects that are challenging to explore through experimentation. Our research is motivated by the desire to comprehend the conditions and parameters influencing the formation, stability, disruption, and reformation of multi-particle sand arches within filter openings. This arching phenomenon serves as an efficient particle retention mechanism, particularly in heavy oil production wells. We delve into factors like particle size, shape, and particle size distribution that may impact multi-particle arch performance. Additionally, we explore the physics behind multi-particle arching by examining the effects of various physical forces on arch performance. Utilizing a Computational Fluid Dynamics–Discrete Element Model, we investigate the multi-particle arching phenomenon under steady-state flow conditions in packed-bed environments. Our approach employs the unresolved coupling method in STAR-CCM+ (Siemens PLM). We test various filter slot geometries, including straight slots, keystone slots, wire-wrapped screens (WWS), and seamed slots, all under laminar flow conditions. Our findings highlight the significance of gravity, inter-particle forces, and interactions between the filter wall and the particles in multi-particle arch formation at both the slot opening and microscale levels. We confirm that a multi-particle arch can be formed within a specific slot width. Interestingly, while maintaining a constant slot width, we observe that the slot length has an insignificant effect on multi-particle arch formation and stability. In summary, our CFD–DEM model successfully simulates and predicts multi-particle arch formation, stabilization, breakage, and reformation, allowing for comprehensive testing of the effects of various parameters. This research offers valuable insights into a complex phenomenon that is crucial in packed-bed filtration systems. [ABSTRACT FROM AUTHOR]

Determining the flame transfer function plays a crucial role during the development phase of lean-burn injectors to predict the overall stability of the combustion system. This study develops an enhanced acoustic post-processing strategy using acoustic network modeling and compressible large-eddy simulation for a lean-burn aero-engine injector in a realistic test rig. Results show that optical flame transfer functions experimentally obtained align with those derived from large-eddy simulation based on heat release rate. However, discrepancies, especially in gain, are observed when using the standard acoustic post-processing method. By employing an acoustic network model, it is shown that comparable flame transfer functions can be achieved through refined post-processing strategies. This study highlights the limitations of conventional acoustic post-processing and underscores the necessity of explicit acoustic modeling in complex setups to accurately obtain the flame response. A generalized formulation applicable to a broader range of setups, extending beyond simple configurations, is presented as an alternative to the conventional acoustic post-processing method. [ABSTRACT FROM AUTHOR]

Surface tension affects all aspects of fluid flow in porous media. Through measurements of surface tension interaction under multiphase conditions, a relative permeability curve can be determined. Relative permeability is a numerical description of the interaction between two or more fluids and the porous media. It is a critical parameter for various tools that characterize subsurface multiphase flow systems, such as numerical simulation for carbon sequestration, oil and gas development, and groundwater contamination remediation. Therefore, it is critical to get a good statistical distribution of relative permeability in the porous media under study. Empirical formula for determining relative permeability from capillary pressure are already well established but do not provide the needed flexibility that is required to match laboratory-derived relative permeability curves. By expanding the existing methods for calculating relative permeability from capillary pressure data, it is possible to create both two and three-phase relative permeability curves. Mercury intrusion capillary pressure (MICP) data from the Morrow 'B' Sandstone coupled with interfacial tension and contact angle measurements were used to create a suite of relative permeability curves. These curves were then calibrated to a small sample of existing laboratory curves to elucidate common fitting parameters for the formation that were then used to create relative permeability curves from MICP data that does not have an associated laboratory-measured relative permeability curve. [ABSTRACT FROM AUTHOR]

The appropriate design and operation of spillways are critical for dam safety. To enhance design practices and gain insights into flow hydraulics, both experimental and numerical modeling are commonly employed. In this study, we conducted a numerical investigation of flow over a mildly sloping (1V:3H) stepped spillway with various step geometries using a multi-phase mixture model with dispersed interface tracking in ANSYS Fluent. The model was validated against experimental data from Utah State University, focusing on water surface profiles over the crest, velocities, and air concentrations. The validated numerical model was used to simulate flow over different step geometries (i.e., 0.2 m H uniform Step, 0.1 m H uniform step, non-uniform steps, adverse slope steps, and stepped pool) for a range of discharges from 0.285 m3/s/m to 1.265 m3/s/m. While flow depths over the crest and velocities in the chute compared well with experimental results, air concentrations exhibited some deviation, indicating numerical limitations of the solver. The shift in the location of the inception point was found to be mainly influenced by a higher flow rate than the different design configurations over an identical mild slope. The downstream non-linear flow velocity curve with different flow rates indicated less effectiveness of the step roughness over a high flow rate as a result of the reduction in relative roughness. The theoretical velocity ratio indicated the least reduction in downstream velocity with the stepped pooled spillway due to the formation of a "stagnant pool". A higher negative-pressure region due to flow separation at the vertical face of the steps was obtained by adverse slope steps, which shows that the risk of cavitation is higher over the adverse slope step spillway. Turbulent kinetic energy (TKE) was found to be higher for uniform 0.2 m H steps due to the strong mixing of flow over the steps. The least TKE was found at the steps of the stepped pool spillway due to the formation of a "stagnant pool". Uniform 0.2 m H steps achieved the maximum energy dissipation efficiency, whereas the stepped pool spillway obtained the least energy dissipation efficiency, introducing higher flow velocity at the stilling basin with a higher residual head. The adverse slope and non-uniform steps were found to be more effective than the uniform 0.1 m H steps and stepped pool spillway. The application of uniform steps of higher drop height and length could achieve higher TKE over the steps, reducing the directional flow velocity, which reduces the risk of potential damage. [ABSTRACT FROM AUTHOR]

We analyze a diffuse interface model for multi-phase flows of N incompressible, viscous Newtonian fluids with different densities. In the case of a bounded and sufficiently smooth domain existence of weak solutions in two and three space dimensions and a singular free energy density is shown. Moreover, in two space dimensions global existence for sufficiently regular initial data is proven. In three space dimension, existence of strong solutions locally in time is shown as well as regularization for large times in the absence of exterior forces. Moreover, in both two and three dimensions, convergence to stationary solutions as time tends to infinity is proved. [ABSTRACT FROM AUTHOR]

We consider steady-state immiscible and incompressible two-phase flow in porous media. It is becoming increasingly clear that there is a flow regime where the volumetric flow rate depends on the pressure gradient as a power law with an exponent larger than one. This occurs when the capillary forces and viscous forces compete. At higher flow rates, where the viscous forces dominate, the volumetric flow rate depends linearly on the pressure gradient. This means that there is a crossover pressure gradient that separates these two flow regimes. At small enough pressure gradient, the capillary forces dominate. If one or both of the immiscible fluids percolate, the volumetric flow rate will then depend linearly on the pressure gradient as the interfaces will not move. If none of the fluids percolate, there will be a minimum pressure gradient threshold to mobilize the interfaces and thereby get the fluids moving. We now imagine a core sample of a given size. The question we pose is what happens to the crossover pressure gradient that separates the power-law regime from the high-flow rate linear regime and the threshold pressure gradient that blocks the flow at low pressure gradients when the size of the core sample is increased. Based on analytical calculations using the capillary bundle model and on numerical simulations using a dynamical pore-network model, we find that the crossover pressure gradient and the threshold pressure gradient decrease with two distinct power laws in the size. This means that the power-law regime disappears in the continuum limit where the pores are infinitely small compared to the sample size. [ABSTRACT FROM AUTHOR]

Electrical capacitance volume tomography (ECVT) is an experimental technique capable of reconstructing 3D solid volume fraction distribution inside a sensing region. This technique has been used in fluidized beds as it allows for accessing data that are very difficult to obtain using other experimental devices. Recently, artificial neural networks have been proposed as a new type of reconstruction algorithm for ECVT devices. One of the main drawbacks of neural networks is that they need a database containing previously reconstructed images to learn from. Previous works have used databases with very simple or limited configurations that might not be well adapted to the complex dynamics of fluidized bed configurations. In this work, we study two different approaches: a supervised learning approach that uses simulated data as a training database and a reinforcement learning approach that relies only on experimental data. Our results show that both techniques can perform as well as the classical algorithms. However, once the neural networks are trained, the reconstruction process is much faster than the classical algorithms. [ABSTRACT FROM AUTHOR]

The production of natural gas hydrates will change the cementation strength, porosity, and effective stress in the stratum, which may lead to engineering and geological disasters. Sand production is a phenomenon where sand particles are carried out of the reservoir along with fluids during gas extraction, posing challenges to safe and sustainable production. This study explored the mechanism of fine particle migration in multiphase flow by a microscopic visualization test device. The device can inject a gas–liquid–solid phase at the same time and allow real-time observation. Experimental tests on fine particle migration of single- and two-phase fluid flow were carried out considering different conditions, i.e., fine particle concentration, fine particle size, fluid flow rate, and gas–liquid ratio. The results show that in single-phase fluid flow, the original gas will gradually dissolve in the liquid phase, and finally stay in the test device as bubbles, which can change the pore structures, resulting in the accumulation of fine particles at the gas–liquid interface. In two-phase fluid flow with mixed gas–water fluids, there are two flow modes of gas–liquid flow: mixed flow and separated flow. The interfacial tension at the gas–liquid interface can effectively migrate fine particles when the gas–liquid flows alternately and the sand production rate further increases as the gas–liquid ratio increases. In addition, changes in the concentration of fine particles, particle size, fluid flow rate, and the gas–liquid ratio will affect the migration of fine particles, leading to differences in the final sand production. [ABSTRACT FROM AUTHOR]

In the present study, a computational methodology based on computational fluid dynamics (CFD) is developed to investigate free surface film flow and its subsequent disintegration on a rotary disk atomizer. The present study provides an insight into efficiently modeling both liquid film formation and its subsequent disintegration. The presented computational methodology can easily be reproduced and can act as a benchmark for the modeling of liquid film formation as well as the disintegration phenomenon. The influence of disk speed, liquid flow and feed arrangement on the rotating disk are investigated. The film thickness profile on the disk resembles the formation of spiral waves at 500 RPM and an irregular breakup of the spiral waves for a disk speed of 1000 RPM. At higher speeds, a smooth and thin liquid film is observed on the disk. Offset feeding of the liquid on the disk alters the wave formation and breakup of the spiral waves. It is found that ligaments are formed at the lip of the disk owing to Rayleigh--Taylor instability, whereas liquid sheet breakup is due to combined rim and wave disintegration for the parameters investigated in this study. [ABSTRACT FROM AUTHOR]

A novel mixed enriched finite element model is developed for coupled non‐linear thermo‐hydro‐mechanical simulation of fractured porous media with three‐phase flow and thermal coupling. Simulation of induced acoustic emission (AE) and microseismic emission (ME) due to tensile fracturing and shear slip instability of pre‐existing fracture interfaces is carried out and the numerical results of the emitted signals are analysed. The mathematical model is based on the generalized Biot's theory for coupled interaction of solid and fluid phases. A computationally robust non‐linear solver is developed to handle the severe non‐linearities arising from fluid saturations, relative permeabilities of fluids, constitutive models of interfaces and convective thermal coupling. To model pre‐existing natural fractures and faults, discrete fracture propagation and nucleation of cracks (micro‐cracking) independently of the original mesh topology, a local Partition‐of‐Unity (PU) finite element method, namely, the Phantom Node Method (PNM) is implemented. The cohesive fracture modelling scheme is implemented to account for the non‐linear behaviour of fracturing and localization, and to rectify the non‐physical stress singularity condition at the fracture tip. Effects of different system parameters on fracturing, shear‐slip instability and the associated induced AEs and MEs are investigated through various numerical results. [ABSTRACT FROM AUTHOR]

Despite their diverse applications, experimental studies on multi-phase flow with phase change in fractured porous media are rare in the literature. In this study, water condensation of vapor in a fractured sandstone is investigated by means of 3D rapid in situ neutron tomography (30 s per tomogram). A water vapor and air mixture is injected at a constant rate, and the accumulation of condensed water is characterized through neutron tomography. Both phase-contrast and absorption-contrast X-ray tomography are jointly used to study the microstructure of the sandstone and measure the morphology of the splitting crack. The interplay between the pore matrix and fissure on the spatiotemporal distribution of water is studied through a combination of these techniques. The condensed water accumulates at the inlet boundary and gradually diffuses into the sample. Once the extracted crack is correctly aligned with with the neutron tomographies (registered), a propensity is seen for water to accumulate in small crack openings close to the cracks and migrate into the porous matrix predominantly due to the capillary effect. When enough liquid water condenses beyond a critical content, the air pressure in the crack transfers it into the porous matrix. This results in higher water content away from the crack. The water front propagates both along and transversely to the crack at a linear rate, albeit at different velocities. The final water distribution is found to be the result of two competing processes: condensation, occurring predominantly in the crack, and diffusion toward the matrix due to the capillary effect, as well as the pressure acting on the bottom of the sample and the crack walls. [ABSTRACT FROM AUTHOR]

In the present study, a computational methodology based on computational fluid dynamics (CFD) is developed to investigate free surface film flow and its subsequent disintegration on a rotary disk atomizer. The present study provides an insight into efficiently modeling both liquid film formation and its subsequent disintegration. The presented computational methodology can easily be reproduced and can act as a benchmark for the modeling of liquid film formation as well as the disintegration phenomenon. The influence of disk speed, liquid flow and feed arrangement on the rotating disk are investigated. The film thickness profile on the disk resembles the formation of spiral waves at 500 RPM and an irregular breakup of the spiral waves for a disk speed of 1000 RPM. At higher speeds, a smooth and thin liquid film is observed on the disk. Offset feeding of the liquid on the disk alters the wave formation and breakup of the spiral waves. It is found that ligaments are formed at the lip of the disk owing to Rayleigh–Taylor instability, whereas liquid sheet breakup is due to combined rim and wave disintegration for the parameters investigated in this study.

In this study, the species transport and functional characteristics of a Proton Exchange Membrane Fuel Cell (PEMFC) using the agglomerate model are carried out. The modeling is two-dimensional and a two-phase flow is provided to separate liquid water and gas inside the fuel cell. The water transfer modeling is carried out using three mechanisms of vapor, liquid water, and dissolved water through the membrane. The entropy generations due to viscous loss, heat transfer, Ohmic losses, mass transfer, and latent heat are obtained. The effects of agglomerate radius, active layer thickness, permeability, and porosity on the current density, species transport, power density, liquid water, temperature distribution, and entropy generation are investigated. The results show that permeability has a significant effect on water management formed in the cathode gas diffusion layer. Also, the total entropy generation is more evident at the low voltages. The findings show that using a smaller agglomerate radius and larger active layer thickness has a better effect on the current density and thus results in higher power density. At 0.7 V, as the agglomerate radius doubles, the current decreases by 41 %. At 0.6 V, however, a 34 % increase in power density is seen in the minimum agglomerate radius.

PAGs are now being considered as the lubricating oil in R290 room air conditioners (RAC) owing to their low pour points and low solubility with R290. However, little research concerning the flow characteristics and migration behavior of the partly miscible PAG in the R290 RAC during dynamics processes has been reported. In this study, visual observation was conducted to analyze the migration of oil during startup and defrosting process. Results show that, during startup process, though excessive oil was discharged from saturated compressor, annular oil film and oil crystal was observed at EEV outlet, the oil can finally return to compressor in the form of linear flow when system parameters gradually reached equilibrium, even though at extremely low ambient temperature. During defrosting processes, the separated oil droplets were found at the EEV inlet when the RAC switched from heating to defrosting, or from defrosting to re-heating mode. The observed adhesion behavior of these oil droplets near EEV increased the potential risk of oil blockage. The larger EEV opening was supposed to be used during this period to increase the reliability of RAC. [ABSTRACT FROM AUTHOR]

Recent developments in Liquid Metal Magnetohydrodynamic systems show that the self-evaporating magnetohydrodynamic system is a promising power generator that converts heat directly into electricity dispensing with a mixer and separator found in conventional systems. The vaporized fraction generated by heating the working liquid metal, drives the remaining liquid by a vapor ejector action. Aiming at higher power density, and higher conversion effectiveness for Liquid Metal Magnetohydrodynamic, we investigate the utilization of a circumferential annular ejector instead of the commonly used central axial ejector. For that purpose, we use Computational Fluid Dynamics to carry out a parametric study that includes the variations in annular ejector geometry, input heating power, and the mass fraction of the ejector flow. In addition, spatial distributions of the velocity, pressure, temperature, and liquid and vapor fractions are presented and analyzed. For an optimized study case, the circumferential annular ejector increased the output power by 8.7 % more than the central axial ejector. [ABSTRACT FROM AUTHOR]

The Ladle Shroud has become an important part of secondary steelmaking, with its role in reducing liquid steel contamination and process improvements. Due to the inherent negative pressure at the lower nozzle–Ladle Shroud joint, it is well known that Ladle Shrouds, protecting steel flows between a Ladle and a tundish below, can suffer from inadvertent ingress of air. Therefore, there is a need to apply inert gas injection at the joint. In the present paper, 3D transient multi-phase simulations of flows occurring for a Reverse Tapered Ladle Shroud during start-up were studied using CFD software ANSYS Fluent 19.1. This allowed us to study the initial multi-phase flow developed during the start-up and potential steel reoxidation, based on a first principles approach. Time-dependent phase fields as well as attendant velocity and turbulence fields were obtained, resulting in the prediction of a turbulent multi-phase flow during start-up and filling. Additionally, some transient phenomena like steel splashing and air suction were observed mathematically. A full-scale water model of the Ladle Shroud was used to qualitatively validate the initial multi-phase turbulent flow inside the Ladle Shroud, in the absence of inert gas injection. [ABSTRACT FROM AUTHOR]

Clustering of flexible fibers in riser flows is investigated using a hybrid approach of Discrete Element Method and Computational Fluid Dynamics. Unlike spherical particles, the flexible fibers possess elongated shape, undergo significant deformation, and dissipate kinetic energies through rapid fiber deformation. The present studies show that these distinct features have significant impacts on the cluster characteristics of the fibers. A larger fiber aspect ratio leads to larger number and sizes of agglomerates, while it causes a reduction in heterogeneity of solids distribution due to the more dilute clusters with reduced packing densities. As the fibers become more flexible, the heterogeneity increases, and denser clusters are obtained. More significant effects of the fiber flexibility on the clustering are observed for the fibers with larger aspect ratios. The increased energy dissipation through the rapid fiber deformation enhances the clustering by augmenting the number and size of the agglomerates. [ABSTRACT FROM AUTHOR]

The production of natural gas hydrates will change the cementation strength, porosity, and effective stress in the stratum, which may lead to engineering and geological disasters. Sand production is a phenomenon where sand particles are carried out of the reservoir along with fluids during gas extraction, posing challenges to safe and sustainable production. This study explored the mechanism of fine particle migration in multiphase flow by a microscopic visualization test device. The device can inject a gas–liquid–solid phase at the same time and allow real-time observation. Experimental tests on fine particle migration of single- and two-phase fluid flow were carried out considering different conditions, i.e., fine particle concentration, fine particle size, fluid flow rate, and gas–liquid ratio. The results show that in single-phase fluid flow, the original gas will gradually dissolve in the liquid phase, and finally stay in the test device as bubbles, which can change the pore structures, resulting in the accumulation of fine particles at the gas–liquid interface. In two-phase fluid flow with mixed gas–water fluids, there are two flow modes of gas–liquid flow: mixed flow and separated flow. The interfacial tension at the gas–liquid interface can effectively migrate fine particles when the gas–liquid flows alternately and the sand production rate further increases as the gas–liquid ratio increases. In addition, changes in the concentration of fine particles, particle size, fluid flow rate, and the gas–liquid ratio will affect the migration of fine particles, leading to differences in the final sand production.

One canonical practice in the development and application of level set methods is to convect a shape represented by zero level set with a given, reversible, and periodic velocity field and test how well the original shape is recovered after each cycle. In this short letter, we mathematically show that Crank–Nicolson time integration, combined with standard Galerkin finite element, can exactly recover the original shape after each cycle, regardless of spatiotemporal resolution. This surprising finding is also numerically demonstrated by LeVeque's problem. [ABSTRACT FROM AUTHOR]

The dynamic response of rocks to thermal, hydrodynamical, mechanical, and geochemical solicitations is of fundamental interest in several disciplines of geosciences, including geo-engineering, geophysics, rock physics, hydrology, mineralogy, and environmental and soil sciences. From crystal shape to rock microstructure or pore space and fluid distribution, parameters characterizing the rock physico-chemical properties evolve at different time and spatial scales. X-ray micro-tomography (XMT), as a non-invasive and non-destructive imaging technique, offers an unprecedented opportunity to add the fourth dimension, i.e. time, to the three-dimensional spatial visualization of rock and mineral microstructures. The technique is increasingly used to explore dynamic processes in porous and fractured rocks, thanks to synchrotron sources and laboratory XMT scanners, new generations of detectors, and increasing computational power. Image processing allows for tracking the evolution of the fluid–fluid or fluid–mineral interfaces as well as measuring incremental deformations, as rocks deform and react through time under in situ conditions of the sub-surface. Here, we review recent advances in 4D X-ray micro-tomography applied to thermo-hydro-mechano-chemical (THMC) sub-surface processes where fluids, porosity, minerals, and rock microstructures evolve together.

Particle-laden gas flows occur in a wide variety of process technologies. It is therefore a common safety scenario to understand how many particles will escape in the event of a leak or emergency pressure relief. Therefore, a vessel filled with gas and homogeneously dispersed solid particles was considered. The aim was to derive a model to describe the discharge of arbitrary spherical particles. For this purpose, multiple numerical simulations were performed with ANSYS CFX©. A cylindrical vessel with a volume of 2 m³, a 25 mm opening and a length to diameter ratio of 2 was considered. The system was considered adiabatic, isentropic, compressible, and subcritical with an ideal gas. The velocity field was described with a one-way Euler-Lagrange method. The particle density, particle size, the gas in the vessel, as well as the initial temperature and pressure in the vessel were varied. Based on a dimensional analysis a model was developed to estimate the discharged mass of particles. This model achieves a small mean absolute deviation from the simulation data of −0.03%. The prediction model is thus able to correctly represent all variables varied without having to carry out single complex numerical simulations. The model is the first model to derive the discharge behaviour of particles from pressure vessels.

[Display omitted] Hypothesis : The migration of supercritical CO 2 (scCO 2) injected into underground reservoirs as part of carbon capture and storage is influenced by organic contamination affecting mineral wettability. Molecular dynamics (MD) simulations of relevant systems that incorporate representative organic solutes allow detailed investigation of changes in fundamental interfacial and capillary properties. Experiments : We use MD simulations to explore the effects of four organic solutes (quinoline, decanoic acid, coronene, sorgoleone) on the wettability of quartz by water in the presence of scCO 2. We examine the impacts of polar, alkyl, and aromatic moieties as well as fluid flow velocity at elevated temperatures and pressures. Findings : Organic molecules accumulate at the water-CO 2 interface, where they distribute according to their size and functional groups. Certain organics penetrate the adsorbed water film at the quartz-CO 2 interface, revealing two modes of hydrogen bonding between polar organic functional group, water, and quartz surface –OH groups. Interfacial energies and contact angles are minimally impacted by organic adsorption at the water-CO 2 interface, possibly due to simultaneous CO 2 desorption. Non-equilibrium MD simulations reveal that flow-induced redistribution of organic compounds modulates the radii of curvature of the advancing and receding water-CO 2 interfaces. Our results indicate that organic adsorption on water surfaces is likely ubiquitous during multi-phase flow in soils and sedimentary rocks, with implications for the mobilization and transport of organic compounds. [ABSTRACT FROM AUTHOR]

Aiming at the simulation of multi-phase flow in the wellbore during the processes of gas kick and well killing of complex-structure wells (e.g., directional wells, extended reach wells, etc.), a database including 3561 groups of experimental data from 32 different data sources is established. Considering the effects of fluid viscosity, pipe size, interfacial tension, fluid density, pipe inclination and other factors on multi-phase flow parameters, a new gas-liquid two-phase drift flow relation suitable for the full flow pattern and full dip range is established. The distribution coefficient and gas drift velocity models with a pipe inclination range of −90°–90° are established by means of theoretical analysis and data-driven. Compared with three existing models, the proposed models have the highest prediction accuracy and most stable performance. Using a well killing case with the backpressure method in the field, the applicability of the proposed model under the flow conditions with a pipe inclination range of −90°–80° is verified. The errors of the calculated shut in casing pressure, initial back casing pressure and casing pressure when adjusting the displacement are 2.58%, 3.43%, 5.35%, respectively. The calculated results of the model are in good agreement with the field backpressure data.

We present a fully Lagrangian particle level-set method based on high-order polynomial regression. This enables meshfree simulations of dynamic surfaces, relaxing the need for particle-mesh interpolation. Instead, we perform level-set redistancing directly on irregularly distributed particles by polynomial regression in a Newton-Lagrange basis on a set of unisolvent nodes. We demonstrate that the resulting particle closest-point (PCP) redistancing achieves high-order accuracy for 2D and 3D geometries discretized on irregular particle distributions and has better robustness against particle distortion than regression in a monomial basis. Further, we show convergence in classic level-set benchmark cases involving ill-conditioned particle distributions, and we present an example application to multi-phase flow problems involving oscillating and dividing droplets. • We accurately approximate closest points on surfaces from point-cloud data. • This enables level-set redistancing in Lagrangian particle methods. • We use polynomial regression in Newton-Lagrange basis on a set of unisolvent nodes. • We show results for basic geometries, spiraling vortex, and multi-phase hydrodynamics. • We compare with a Smoothed Particle Hydrodynamics colorfield approach. [ABSTRACT FROM AUTHOR]

While multiphase flows are abundant in both natural environments and engineering applications, their analysis and quantification present challenges. In particular, simultaneously measuring the flow field and quantifying particle behavior pose many challenges. Methods based on Particle Image Velocimetry (PIV) and Particle Tracking Velocimetry (PTV) principles have been used in the last two decades to measure flow fields and dispersed (particle) phases, respectively. Despite the extensive application of these principles to multiphase flow, there are numerous approaches and techniques used to synchronize and combine PIV and PTV measurements. Combined PIV and PTV data acquisition also requires consideration of phase discrimination to obtain distinct data for the fluid and dispersed phases. In the literature, various methods have been proposed and applied to achieve phase discrimination. This review paper aims to consolidate and classify various phase discrimination techniques used in specialized applications in hydraulic engineering. These methods are categorized into optical (spectral, temporal, and hybrid) and post-processing methods, with a particular emphasis on their applicability within the realm of hydraulic engineering. Moreover, this review expands on several emerging PIV/PTV technologies and applications, where the combination of equipment and algorithms has led to significant strides in the non-intrusive measurement of multiphase flow. By consolidating and critically evaluating current methods for particle discrimination, this paper aims to enhance the scientific community's understanding of simultaneous phase velocity measurements, thereby setting the stage for advancements in multiphase flow visualization techniques. [Display omitted] • Review of phase discrimination methods based on the underlying techniques from optical to post-processing. • Optical phase discrimination method highlighted as most prevalent, but pose technology and detection limitations. • Options for phase discrimination in processing are discussed, usable alone or with optical phase discrimination. • Examination of emerging PIV/PTV technologies in phase analysis. [ABSTRACT FROM AUTHOR]

• The study expanded the database for surface wettability measurement. • Through the melt infiltration experiment, our work has improved and partially validated infiltration models. The model demonstrate predictive capabilities, thereby advancing our comprehension of melt infiltration dynamics. • The wettability of particulate beds markedly influences melt infiltration dynamics: wettable beds enhance, while non-wettable beds hinder, the initial infiltration process. • Our findings underscore the critical importance of addressing both capillary-driven and gravity-driven flow regimes in melt infiltration models for inclusion in debris bed remelting models. Melt infiltration into porous media is an intriguing phenomenon that holds immense significance across various sciences and technologies. In this work, the problem of metallic melt infiltration in particulate beds is investigated for understanding and prediction of severe accident progression associated with a molten pool penetrating through an underlying debris bed which may form in the reactor core or in the lower head of a light water reactor. The present study aims to quantify the effect of particle surface's wettability on melt infiltration kinetics. For this purpose, two categories of experiment are conceived and carried out to measure the wettability of different material surfaces by melt and to characterize melt infiltration kinetics in one-dimensional particulate beds, respectively. The melt material is tin–bismuth eutectic alloy with a melting point of 139 °C. Copper (Cu), stainless steel (SS), Tin (Sn) and tin-coated stainless steel (Sn-coated SS) are chosen as materials of substrates and particles in wettability measurement and melt infiltration study. The particulate beds, packed with 1.5 mm spheres, are preheated to 200 °C before the melt infiltration begins. The experimental data of wettability measurement shows that the contact angles of liquid Sn-Bi eutectic on the above-mentioned material surfaces range from 79° to 135°. The results of melt infiltration tests confirm the significant effect of wettability on melt penetration kinetics. The capillary force plays a significant role in the initial infiltration of particulate beds. Specifically, a wettable particulate bed enhances the initial melt infiltration, whereas non-wettable beds hinder it. [ABSTRACT FROM AUTHOR]

In this study, a free energy model of the Lattice Boltzmann Method (LBM) is performed to simulate the motion, deformation, and decomposition of a droplet in the presence of electrohydrodynamic flow in porous media. To simulate the multi-phase flow in the presence of dielectric current by using the LBM, three distribution functions are used. To implement the free energy mode of HCZ, two equilibrium distribution functions are considered, one for solving the Navier-Stokes equation and the other for solving the Cahn-Hillard equation. Initially, the ability of the code to apply surface tension is tested by using the Laplace law and the droplet release test. Results show that there is a linear relation is between surface tension and κ which is a parameter in the HCZ model. The results show that the present numerical program is capable of modeling the regulated surface tension force as well. Then, the Rayleigh–Taylor instability simulation is used to evaluate the code's ability to apply volume forces. Also, the obtained results of the written numerical program are in good agreement with the numerical results of other valid references. Obtained results show that the difference between droplet deformation measured by numerical method and Taylor function is less than 2%. After modeling the droplet motions to investigate the droplet deformation, two electric fields are inserted into the droplet with reverse directions of each other. Then, by various tests, it is shown that at a given potential difference the droplet breaks down after much deformation and is divided into smaller droplets. The decomposition of droplets in a pre-mixed emulsion is a common technique to produce the monodisperse droplets. The presence of monodisperse droplets in an emulsion improves the physical properties of polymer from the science expert's perspective. The results of this study are used to improve the quality of polymer components.

Direct-methanol fuel cell (DMFC) systems are comparatively simple, sometimes just requiring a fuel cartridge and a fuel cell stack with appropriate control devices. The key challenge in these systems is the accurate determination and control of the flow rates and the appropriate mixture of methanol and water, and fundamental understanding can be gained by computational fluid dynamics. In this work, a three-dimensional, steady-state, two-phase, multi-component and non-isothermal DMFC model is presented. The model is based on the Eulerian approach, and it can account for gas and liquid transport in porous media subject to mixed wettability, i.e., the simultaneous presence of hydrophilic and hydrophobic pores. Other phenomena considered are variations in surface tension due to water–methanol mixing and the capillary pressure at the gas diffusion layer–channel interface. Another important aspect of DMFC modeling is the transport of methanol and water across the membrane. In this model, non-equilibrium sorption–desorption, diffusion and electro-osmotic drag of both species are included. The DMFC model is validated against experimental measurements, and it is used to study the interaction between volume porosity of the anode gas diffusion layer and the capillary pressure boundary condition at the anode, and how it affects performance and limiting current density. [ABSTRACT FROM AUTHOR]

Computational fluid dynamics (CFD) coupled with a three-dimensional discrete element method (DEM) was applied to investigate the flow of corn-shaped particles in a cylindrical fluidized bed. The fluid phase was simulated with a k − ε turbulent model, and particle movement was simulated by the DEM. The particle motion coupled with the volume-averaged conservation of mass, momentum, and energy equations over a discretized domain. The corn-shaped particles were constructed as multi spheres (i.e., 4, 6, and 8 spherical elements). The particle-particle and particle-wall interactions were modeled using the Hertz-Mindlin no-slip contact model. The research was focused on the minimum velocity of fluidization (Umf) and pressure drop (ΔP) of the corn particles with three different shapes. Additionally, the influence of the velocity of the fluid and particle shape on heat transfer was investigated. The simulation results showed that Umf increases with an increasing number and arrangement of spherical elements. As the number of particles increases, Umf and ΔPmax increase as well. The minimum fluid velocity of 2 Umf is sufficient for the corn kernels to be thoroughly mixed. [ABSTRACT FROM AUTHOR]

The passage of a bubble and the required energy for its motion through a confining pore can potentially be affected by the surface roughness and geometry of the pore. The motion of an isolated bubble passing through four different pore geometries (three circular pores, a smooth pore and 2 with different roughness, and a sharp triangular pore) is investigated. The shape of the deformed bubble passing these geometries was evaluated to determine the pressure drop across the bubble and hence the driving force to cause motion. The results of investigating the motion of the bubbles and the change in the pressure and velocity of the bubbles showed that the pore shape and surface roughness have a significant effect on the passage of the isolated phase. The motion of the bubble entering the entrance of the circular pores was similar for all circular cases. On exiting, however, a clear difference between the cases due to the presence of the peaks of the roughness was observed. These results indicate that, in addition to the critical pressure at the entrance of the pore, extra resistance will be introduced due to bubble phase pinning at the exit caused by roughness of the pore. [ABSTRACT FROM AUTHOR]

Co-curing composites facesheets to produce sandwich structures involves heating a prepreg-core assembly in a vacuum bag and compacting it by an external pressure until the prepreg cures and bonds to the core. During this process, vacuum pressure can cause atmospheric air in the honeycomb core to bubble through uncured prepreg facesheets and impact material quality, such as excess resin bleed and void growth in either the facesheet or the bondline. In this paper, we propose a multiphase flow model to predict core gas pressure throughout the process. Fully impregnated prepreg facesheets only become permeable to gas as liquid resin desaturates pores in the fabric weave. To solve for the core gas pressure, resin and gas transport equations are solved simultaneously. The permeability of each phase is a function of saturation–defined by the Brooks-Corey model to be a power law function of the capillary pressure. Deviating from a single phase (gas only) model, using dimensionless analysis we identify four material properties which control the outcome: (i) an intrinsic permeability, K i , which only depends on the fabric architecture and is invariant to all process variables (time, temperature, pressure), (ii) the ratio of fluid viscosities, μ w / μ g , where resin viscosity varies strongly with temperature and degree of cure, (iii) a bubbling (capillary) pressure, P b , which defines the minimum pressure needed to penetrate the largest pore, and (iv) a pore size distribution parameter, λ, which defines the percentage of pores which may desaturate given the evolving capillary pressure. Changes in observed gas permeability due to time and temperature are explained by the evolving desaturation of facesheet resin and the known relationship to resin viscosity. By applying this model, a reduced set to material characterization is required and complex process cycles can quickly be interrogated. With our experiments we demonstrate that one single value for K i and one single value for λ can be used to predict the gas pressure decay (time dependent) at different temperatures, confirming that the intrinsic permeability is constant for the fiber network and changes in the relative permeability to air are due to the decrease in viscosity only. The limitations of this model are presented and discussed. [ABSTRACT FROM AUTHOR]

Deep wells control safety problems have always been the focus of attention due to the influence of complicated geological conditions, such as high-temperature and high-pressure (HTHP). Considering the mathematical model is only approximation of reality, thus the continuous transmission of real-time measurements is more popular, which can be used to identify the undetermined downhole parameters and improve accuracy of the model predictions. In the current study, we use two pressure while drilling tools to monitor downhole parameters in real time. Firstly, combined with the unscented-Kalman-filter (UKF) algorithm, a well hydraulics forward model with density factor and friction factor based managed-pressure-drilling (MPD) system is developed to quantitatively analyze the actual transient annular pressure. Secondly, a new multi-phase flow inversion model is established by determining the inversion parameters as gas kick rate and the position of the gas kick, which is used to track the values of pressure and outlet flow rate in real-time. The results of the case indicate that the inversion accuracy of the inversion parameters increases with the distance between dual-measurement points, and the reasonable value is selected as 30 m. Additionally, the proposed model is successfully validated using synthetic data and experimental data, where the maximum errors in predicting the position of the gas kick are only 3.1% and 5.3% when tuning the model stably tends towards the true value, respectively. The proposed model achieves accurate quantitative interpretation and analysis of downhole gas kick conditions, further clarifies the previously unknown key parameters of downhole gas kick, and has important significance for the realization of safe and efficient drilling. [ABSTRACT FROM AUTHOR]

This study develops robust numerical algorithms for the simulation of three-phase (solid-liquid-gas) boiling and bubble formation problems in rectangular channels. The numerical algorithms are based on the Finite Volume Methods (FVM) and implement both the volume-of-fluid (VOF) methods for liquid-gas interface tracking as well as the volume-fraction methods to account for the concentration of embedded solid nano-particles in the liquid phase. Water is used as the base-liquid and the solid phase is modelled via metallic nano-particles (both aluminium oxide and titanium oxide nano-particles are considered) that are homogeneously mixed within the liquid phase. The gas phase is considered as a vapour arising from the bolling processes of the liquid-phase. The finite volume methodology is implemented on the OpenFOAM software platform, specifically by careful modification and manipulation of existing OpenFOAM solvers. The governing fluid dynamical equations, for the three-phase boiling problem, take into account the thermal conductivity effects of the solid (nano-particle), the momentum and energy equations for both the liquid-phase and the gas-phase, and finally the decoupled mass conservation equations for the liquid- and gas- phases. The decoupled mass conservation equations are specifically used to model the phase change between the liquid- and gas- phases. In addition to the FVM and VOF numerical methodologies for the discretization of the governing equations, the pressure-velocity coupling is resolved via the PIMPLE algorithm, a combination of the Pressure Implicit with Splitting of Operator (PISO) and the Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) algorithms. The computational results are presented graphically with respect to variations in time as well as in the nano-particle volume fractions. The simulations and results accurately capture the formation of vapour bubbles in the two-phase (particle-free) liquid-gas flow and additionally the computational algorithms are similarly demonstrated to accurately illustrate and capture simulated boiling processes. The presence of the nano-particles is demonstrated to enhance the heat-transfer, boiling, and bubble formation processes. [ABSTRACT FROM AUTHOR]

Interfacial area is an important factor during two-phase flow in porous media because mass-transfer mechanisms take place at the interfaces of immiscible phases. The objective of this work is to quantify how grain-size distribution affects the temporal development of interfacial area during two-phase flow through porous media. A two-phase lattice Boltzmann model (color gradient method) was used to simulate drainage (displacement of a wetting fluid by a non-wetting fluid) and imbibition (displacement of the non-wetting fluid by the wetting fluid) in an ensemble of two-dimensional porous media samples. Five groups of porous media, each comprising 20 realizations, were characterized by their median grain size (d50) and coefficient of uniformity (Cu). For all 100 realizations, simulations of drainage and imbibition were conducted until steady-state saturation was achieved, and interfacial area was monitored throughout the simulations. During both drainage and imbibition, the interfacial area initially increases with time until reaching a peak area, then decreases, and then plateaus at a steady-state value. Interfacial area is higher during imbibition than during drainage. The temporal evolution of interfacial area, as quantified by peak area and time to reach peak area, was similar in the three groups characterized by small grain size (d50 ≈ 7.7 lattice units) and relatively uniform grain-size distribution (Cu ≈ 1.21, 1.49, 1.85), for both drainage and imbibition. This suggests that, for the fluid conditions considered here, nonuniformity of grain size is not important below a certain threshold value of Cu. However, two groups with larger grain size (d50 ≈ 8.9 lattice units) and relatively nonuniform grain-size distribution (Cu ≈ 1.85, 2.29) exhibited differences from each other, suggesting that nonuniformity of grain size affects interfacial area when Cu is above a certain value. Furthermore, median grain size was observed to have important effects on temporal evolution of interfacial area. [ABSTRACT FROM AUTHOR]

In this paper, we generalize the solid boundary condition where a one-sided Riemann solver is introduced to determine the fluid–solid interaction for weakly compressible smoothed particle hydrodynamics (SPH) presented in Zhang et al. (2017) to model multi-phase flows with large density ratio and multi-phase fluid–structure interaction (FSI) in multi-resolution scenario. Compared with the boundary condition proposed by Adami et al. (2012) where solid is discretized by dummy particles whose physical quantities are extrapolated from surrounding fluid particles, the present method is very simple and efficient as extra extrapolation is avoided by constructing a one-sided Riemann problem for each interacting fluid–solid particle pair. This feature makes its extension to multi-phase flow and FSI straightforward. Furthermore, we adopt a penalty method in multi-resolution discretization to prevent particle penetration in violent multi-phase simulation. A set of examples involving multi-phase flows with high density ratio and complex interface, and multi-phase FSI are studied to demonstrate the accuracy, robustness and versatility of the present method. The validations presented herein and those reported by Zhang et al. (2017) where free-surface flows exhibiting violent events such as impact and breaking are studied indicate that the present method provides a unified approach for addressing the solid, i.e., rigid and flexible, boundary condition in multi-physics SPH applications. [ABSTRACT FROM AUTHOR]

• Application of the Euler-Euler method to CFD modelling of the flow of ice slurry. • Low slip velocity of solid particles. • Highest slip velocities are observed near the channel sidewalls. • Homogeneous flow, lower border velocities for downward compared to upward flow. • Flow map of ice slurry for vertical flow in slit channel. In this article, the Euler-Euler method was applied to CFD modelling of adiabatic ice slurry flow, for different flow directions in a vertical slit channel. The mean relative accuracy of determining pressure drops compared to experimental studies was 5.6%. Calculations showed that the relative slip velocity and the effect of flow direction on slip velocity increase with decreasing carrier fluid concentration, decreasing mean flow velocity, and decreasing mean solid particles volume fraction. The mean particle slip velocity does not exceed 4%, and local slip velocity values can be 58% of the mean suspended solids flow velocity. For heterogeneous flow, the highest slip velocities occur at a distance of 15% of the channel width from the channel sidewalls. The shape of the solid particles distribution profile is determined by the mean flow velocity and the mean solid particles volume fraction. Excluding the area at a distance of 8% of the channel width from the sidewall where local maximum (for low velocities) and minimum (for higher velocities) values may occur, the profile is stabilised in the central part of the channel. In this study, the boundary curves between heterogeneous and homogeneous flow were determined for ice slurry flow in a vertical slit channel. [ABSTRACT FROM AUTHOR]