Multiphase Model Research Articles

Modeling long carbon-chain species formation with porous multiphase models

Context. Recent studies show that multiphase models trap too many volatile species such as CH4 inside ice mantles, so they usually underestimate the abundances of long carbon-chain species observed toward warm carbon-chain chemistry (WCCC) sources. Aims. We propose a new multiphase model that allows more volatile species to diffuse out of the ice mantle upon warming. The new multiphase model is used to study the synthesis of long carbon-chain molecules in WCCC sources. Methods. We included porous structure in the ice mantles. The porous structure can enlarge the active layers of ice mantles so that fewer volatile species are trapped. The porous multiphase models were simulated using an accelerated Gillespie algorithm. Results. The abundances of long carbon-chain species predicted by the porous multiphase models can be more than one order of magnitude higher than those predicted by the multiphase model at temperatures relevant to WCCC sources. Moreover, the porous multiphase models predict more abundant long carbon-chain species as the porosity of the ice mantles increases. On the other hand, the two-phase model still estimates higher long carbon-chain species abundances than the porous multiphase models do. The abundances of long carbon-chain species predicted by our porous multiphase models agree reasonably well with observations toward three WCCC sources, L483, L1527, and B228. Conclusions. Our porous multiphase model solves the problem of too many volatile species being trapped in ice mantles in the multiphase models.

Heat and mass transfer and deformation during chiffon cake baking

The structural transformation from a foam liquid to a porous solid during cake baking involves pore development and solidification, resulting in complex coupled heat transfer, mass transfer, and deformation processes. Studying the mechanisms can provide important references for understanding the physical processes of numerous foods containing gas pores. We constructed a multiphase flow-deformation model for chiffon cake baking, and validated its accuracy by comparing the experimental results of temperature and height. Based on the model, the heat transfer, mass transfer, and deformation characteristics were investigated. In the pore-closed region, the evaporation-diffusion-condensation process of water vapor enhances heat transfer, and its contribution to heat transfer has an equivalent thermal conductivity of up to 0.64 W/(m·K), which increases the heating rate. In the pore-opening region, the water vapor evaporates from the high-temperature, high-water activity region and is transported towards the lower-temperature region and external environment. This process enhances heat transfer and induces an evaporative cooling effect, resulting in a uniform temperature distribution that remains below 100 °C across the majority of the region. Cake expansion occurs in the low-viscosity, pore-closed region, and the water vapor generated at high temperatures serves as the primary driving force source, contributing up to 84.6%.

Four-phase CT lesion recognition based on multi-phase information fusion framework and spatiotemporal prediction module

Multiphase information fusion and spatiotemporal feature modeling play a crucial role in the task of four-phase CT lesion recognition. In this paper, we propose a four-phase CT lesion recognition algorithm based on multiphase information fusion framework and spatiotemporal prediction module. Specifically, the multiphase information fusion framework uses the interactive perception mechanism to realize the channel-spatial information interactive weighting between multiphase features. In the spatiotemporal prediction module, we design a 1D deep residual network to integrate multiphase feature vectors, and use the GRU architecture to model the temporal enhancement information between CT slices. In addition, we employ CT image pseudo-color processing for data augmentation and train the whole network based on a multi-task learning framework. We verify the proposed network on a four-phase CT dataset. The experimental results show that the proposed network can effectively fuse the multi-phase information and model the temporal enhancement information between CT slices, showing excellent performance in lesion recognition.

Multiphase field model of cells on a substrate: From three dimensional to two dimensional

Multiphase field model of cells on a substrate: From three dimensional to two dimensional

COMPARATIVE STUDY USING CFD OF COUNTER-CURRENT AND CO-CURRENT HYDROTREATING REACTORS USING JATROPHA CURCAS L VEGETABLE OIL

In this work, mathematical modeling and CFD simulation of two countercurrent and cocurrent hydrotreatment reactors were carried out, validating the results with a drained bed reactor (TBR), a commercial CoMo/γ-Al2O3 catalyst was used, the material the raw material was Jatropha Curcas L vegetable oil. The operating conditions were temperature 380 ° C, pressure 8 MPag. The kinetic model that was used considered 13 reactions that involve processes of decarboxylation, decarbonization, hydrodeoxygenation and hydrocracking reactions for triolein and tristearin triglycerides. The CFD simulation was carried out in Fluent 18.2 in a transient state and in 3D, considering the standard κ - ε turbulence models, Eulerian multiphase model and porous medium model, it was shown that the countercurrent reactor has less pressure drop than the countercurrent, the conversion the countercurrent reactor has a greater conversion of reactants of 99%, the generation of products from the countercurrent reactor has higher concentrations than the cocurrent reactor, this is because it has more contact areas between phases in the reactor.

Numerical Investigation of Film Formation Characteristics and Mechanisms through Airless Spraying on Spherical Surfaces

This paper focuses on key engineering issues, particularly the overall turbulent transport of paint spray and coating film distribution characteristics, in the process of airless spraying film formation. By deeply considering the geometric features of spherical surfaces and their impact on the near-wall region of the flow field, an airless spraying film formation model consisting of the Eulerian multiphase model, the realizable k–ε turbulence model, and the Eulerian Wall Film model was established. Through numerical simulations of static spraying on the inner and outer walls of spherical surfaces with different radii, the influence of geometric features on the spray flow field and film formation characteristics on spherical surfaces was investigated. Subsequently, based on numerical simulations of dynamic spraying on different nozzle trajectories, the film formation characteristics were analyzed, and the optimal spray trajectory planning method was determined. Additionally, this study examined the coating distribution characteristics during dynamic spraying on spherical surfaces with varying geometric dimensions. Finally, a kind of chlorinated rubber anti-corrosion primer was chosen to carry out spraying experiments, which validated that the airless spray coating model and the corresponding numerical simulation methods established in this paper were reasonable and feasible for investigating the film formation characteristics on spherical surfaces. This work is expected to further promote the application of airless spray techniques in machinery, automotive, shipbuilding, and aviation industries.

Development and validation of a 1D gas–liquid model for dissolved Mn(II) removal by oxidation process in a square bubble column

Modeling multiphase reactors requires an in-depth multidisciplinary analysis of various phenomena including the chemical kinetics, oxygen mass transfer, as well as the simulation of flows within these contactors. In this study, a 1D model of two-phase flow for Mn(II) removal from drinking water by aeration process is developed and validated. This model is based on the Eulerian description of two-phase gas–liquid flow with the comparison between a one-medium bubble size and a two-bubble class description to represent the bubble population in the heterogeneous flow regime. All the relevant chemical species are simulated by coupling hydrodynamics, gas–liquid mass transfer, and reaction kinetic. A pseudo-first-order model accounting for homogeneous and heterogeneous kinetics is considered for Mn(II) oxidation. The performance of the developed 1D model is compared and validated with experimental data. The 1D model was able to predict quantitatively Mn oxidation as a function of pH, initial Mn(II) and initial Mn(IV) concentrations.

Multi-physics modeling of phase change memory operations in Ge-rich Ge2Sb2Te5 alloys

One of the most widely used active materials for phase-change memories (PCM), the ternary stoichiometric compound Ge2Sb2Te5 (GST), has a low crystallization temperature of around 150°C. One solution to achieve higher operating temperatures is to enrich GST with additional germanium. This alloy crystallizes into a polycrystalline mixture of two phases, GST and almost pure germanium. In a previous work [R. Bayle et al., J. Appl. Phys. 128, 185 101 (2020)], this crystallization process was studied using a multi-phase field model (MPFM) with a simplified thermal field calculated by a separate solver. Here, we combine the MPFM and a phase-aware electrothermal solver to achieve a consistent multi-physics model for device operations in PCM. Simulations of memory operations are performed to demonstrate its ability to reproduce experimental observations and the most important calibration curves that are used to assess the performance of a PCM cell.

3D mesoscale model of steel fiber reinforced concrete based on equivalent failure of steel fibers

Steel fiber reinforced concrete (SFRC) is widely used in civil engineering. Investigating the mechanical properties and failure mechanisms of SFRC materials using mesoscopic models holds significant theoretical and practical importance. The bond-slip interaction between steel fibers and the cementitious matrix is crucial, yet current computational capabilities struggle to simulate the interactions among the numerous components within concrete containing a large number of steel fibers. This paper establishes an equivalent failure model to replace the bond-slip interaction. Based on this model, a multiphase mesoscopic model (including aggregates, the interfacial transition zone (ITZ), mortar, and steel fibers) is developed to predict the mechanical properties and failure modes of SFRC. The accuracy and validity of the model are verified by comparing the simulation results with the experimental results from four-point bending tests on SFRC beams, focusing on load-displacement curves, failure modes, and crack propagation. The results indicate that under load, the ITZ at the sharp edges of large aggregates in the SFRC beam is the first to be damaged, forming microcracks. Subsequently, these cracks bypass the large particles and propagate towards weaker regions with fewer steel fibers, forming macrocracks. At this stage, the steel fibers take over the load from the cementitious matrix and limit crack propagation. The simulated crack propagation trend and crack width during the loading process of the SFRC multiphase mesoscale model match well with the experimental observations. A higher fiber content can mitigate stress concentration within SFRC beams and enhance the fiber bridging effect, significantly improving the flexural load-bearing capacity and toughness of the beams. A smaller steel fiber inclination angle can effectively inhibit the propagation of vertical cracks, thereby increasing the load-bearing capacity and toughness of SFRC beams and extending the service life of the structure.

Single and multi-threaded power flow algorithm for integrated transmission-distribution-residential networks

The rapid development of renewable sources has significantly increased interdependencies between electricity networks of all voltage levels, leading to bidirectional flows between transmission and distribution networks, and requiring analysis of Integrated Transmission-Distribution (ITD) network. The interconnectivity is further amplified by additional coupling with electricity, gas, heat and hydrogen networks, on both national and regional levels. Moreover, installation of solar, wind and storage on customers’ premises has indicated that residential networks need to be included in the overall integrated model, called Integrated Transmission-Distribution-Residential (ITDR) network. The main goal of the paper is to develop a general model of the ITD/ITDR networks and to solve the power-flow problem on large-scale networks in an efficient way. The general model includes three-phase transmission and multi-phase distribution models, as well as accurate control strategies for traditional and electronically coupled electricity resources. The proposed model is solved via novel single-threaded power flow procedure, which incorporates new network elements’ models and the developed algorithm for integrated power flow calculations in different domains. This is further improved by developing a multi-threaded approach. Analyses on a small-scale ITD network have shown that single- and multi-threaded approaches are, respectively, (1.5–4) and (2–5) times faster compared to the state-of-the-art procedures. As network size increases, the efficiency of the proposed multi-threaded procedure becomes more pronounced compared to the single-threaded one (up to 2.39 times).

Numerical simulation on the condensation heat transfer and flow characteristics outside smooth and enhanced tubes

Most of the current studies only conducts two-dimensional simulations of condensation heat transfer and flow outside enhanced tubes, which cannot accurately reflect the flow and heat transfer characteristics of liquid film outside enhanced tubes. In order to provide theoretical support for the design optimization of enhanced tubes, this study adopts the VOF multiphase model and Lee condensation model to simulate the condensation heat transfer(HTC) of refrigerants outside smooth and enhanced tubes. The instantaneous film flow characteristics of the liquid film outside the horizontal smooth and enhanced tubes are analyzed, and the thickness of the liquid film and the relationship with the condensation heat transfer coefficient of the smooth and enhanced tubes under different working conditions are calculated. The refrigerants are compared under the same working conditions, and the results are shown: The simulation results are in good agreement with the experimental data and the Nusselt analytical solution, and the error is all within 15%; the distribution of liquid film is highly sensitive to the magnitude of local condensation heat transfer coefficients, and the condensation HTC outside the enhanced tube is approximately six times of that of smooth tube. Combining the distribution of the liquid film and the thermophysical properties of the refrigerants, it was determined that R410A has the highest HTC, while R1234yf has the lowest HTC.

Numerical Simulation of Gas Atomization and Powder Flowability for Metallic Additive Manufacturing

The quality of metal powder is essential in additive manufacturing (AM). The defects and mechanical properties of alloy parts manufactured through AM are significantly influenced by the particle size, sphericity, and flowability of the metal powder. Gas atomization (GA) technology is a widely used method for producing metal powders due to its high efficiency and cost-effectiveness. In this work, a multi-phase numerical model is developed to compute the alloy liquid breaking in the GA process by capturing the gas–liquid interface using the Coupled Level Set and Volume-of-Fluid (CLSVOF) method and the realizable k-ε turbulence model. A GA experiment is carried out, and a statistical comparison between the particle-size distributions obtained from the simulation and GA experiment shows that the relative errors of the cumulative frequency for the particle sizes sampled in two regions of the GA chamber are 5.28% and 5.39%, respectively. The mechanism of powder formation is discussed based on the numerical results. In addition, a discrete element model (DEM) is developed to compute the powder flowability by simulating a Hall flow experiment using the particle-size distribution obtained from the GA experiment. The relative error of the time that finishes the Hall flow in the simulation and experiment is obtained to be 1.9%.

Beyond symmetry: Investigating asymmetric melt pool evolution in multi-pulse laser surface melting

A numerical investigation is carried out to explore the intricacies of multi-pulse pulsed laser surface melting (pLSM) to understand its impact on surface evolution. A finite-element-based multi-phase model with temperature-dependent properties is employed to track the interface for multiple laser pulses. Examining various overlap spacings and conducting a comparative analysis of the number of pulses, the study focuses on the exclusive influence of overlapping in surface texture generation. Notably, the assumption of an initially flat surface eliminates the effects of the initial surface roughness to provide unique insights completely based on multi-pulse dynamics. While the first pulse on a flat initial surface resulted in a symmetric surface evolution, asymmetric melt pools were observed in the second pulse and subsequent pulses. The asymmetry results from non-uniform cooling and melt pool flows influenced by the surface evolved in the first pulse. The topography-driven surface tension from the first pulse made the trailing peak solidify slower than the leading peak. The asymmetry was significant for smaller overlaps between the two pulses and reduced as the overlap increased. Further, an increase in the number of laser pulses promotes the generation of identical asymmetric surface features. In conclusion, the study demonstrates the importance of the developed model in accurately predicting the surface evolution influenced by topography-driven surface tension and that single pulse axisymmetric models are insufficient.

Characteristics and optimization strategy of microwave thermal regeneration of spent activated carbon based on a multi-physical field model

Microwave thermal regeneration is an efficient and low-consumption way to recycle spent activated carbon. However, traditional experimental approaches are difficult to analyze the electromagnetic field distribution in the microwave cavity, heat and mass transfer process of adsorbates, and optimization of the microwave reactor. Therefore, in this work, a multi-phase porous media model coupled with electromagnetism, heat and mass transfer is established to study the characteristics of microwave thermal regeneration procedure and to propose an optimization strategy for the microwave reactor. The results showed that the absorption of microwave by the sample can be strengthened by adjusting the width to height ratio of the waveguide. The optimal waveguide size (width: length = 80 mm: 10 mm) increased the microwave utilization efficiency from 65.4 % to 98.5 %. In addition, the combination of rotary and intermittent microwave heating significantly optimized the temperature uniformity in both lateral and vertical directions and reduced the microwave heating time. The combined microwave heating time was reduced from the initial 136 s to 80 s, saving 41 % of energy consumption. The temperature difference of the sample was also reduced from the initial 536 K to 191 K, and the covariance COVT decreased from 0.52 to 0.24. The results provide a valuable technical guideline for the optimization of the microwave reactor in order to improve the regeneration efficiency and the quality of the regenerated carbon.

Influence of the number of guide vane blades on the energy conversion characteristics of gas-liquid mixing pumps

Abstract To investigate the optimal number of guide vanes for peak performance efficiency in a mixing pump, this study employs a self-engineered gas-liquid mixing pump to the principal subject of analysis. adopts SST κ -ω turbulence model, Euler multiphase flow model and SIMPLEC algorithm, and conducts three-dimensional flow field numerical simulation under five operating conditions with the number of guide vane of the gas-liquid mixing pump as 5, 7, 9, 11, 13, 15, and 17, and the volume gas content as 10% to 50%, respectively. Volume gas content were 10% ∼ 50% of the five conditions for three-dimensional flow field numerical simulation, the experimental findings indicate that: with an increase in the number of guide vane blades, the efficiency of the pump’s secondary impeller varies in a cubic function relationship. When the gas content at the inlet is between 10% and 20%, efficiency is highest with 9 blades. When the gas content at the inlet is between 30% and 50%, efficiency is highest with 15 blades. Additionally, when there are 9 blades, the head of the secondary impeller reaches its maximum at different gas contents at the inlet.

Modelling of wall-bounded cavitating flow and spray mixing in multi-component environments using the PC-SAFT equation of state

This work introduces a numerical multiphase model for multi-component mixtures, utilizing tabulated data for physical and transport properties across a spectrum of conditions from near-vacuum pressures to supercritical states. The property data are derived using Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT), vapor-liquid equilibrium (VLE) calculations, entropy scaling methodologies, and Group Contribution (GC) methods. These techniques accurately reflect the thermodynamic behaviors of real fluids, avoiding the empirical estimation of Equation of State (EoS) input parameters. Implemented in OpenFOAM, the fluid dynamics solver is designed to address the three-dimensional Navier-Stokes equations for multi-component mixtures. The methodology integrates operator splitting to manage hyperbolic and parabolic steps distinctively. Hyperbolic terms are solved using the HLLC (Harten-Lax-van Leer-Contact) solver with temporal integration performed via a third-order Strong-Stability-Preserving Runge–Kutta (SSP-RK3) method. Viscous stress tensor contributions in the momentum equation are handled through an implicit velocity correction equation, while parabolic terms in the energy equation are explicitly solved. The simulation efficiency is further enhanced by adaptive Local Time Stepping and the Immersed Boundary (IB) method, which addresses interactions between the fluid and solid boundaries. Turbulence is resolved using the Wall Adaptive Large Eddy (WALE) model. Applied to high-pressure diesel fuel spray injections into non-reacting (nitrogen) gas environments, the model has been validated against Engine Combustion Network (ECN) data for the Spray-C configuration, featuring a fully cavitating multi-hole orifice. Results demonstrate that the model achieves accurate predictions across a broad range of tested conditions without the need for tuning or calibration parameters.

Numerical Investigation of the Fuel Tank Sloshing Condition of a Commercial Vehicle

This study investigates the impact of baffles on fuel sloshing behavior within truck fuel tanks using numerical simulations. The volume of the fluid multiphase model is employed to analyze the flow dynamics of 25% diesel fuel in a 250 L tank, modeled in a 3D domain. Two configurations were compared: a tank with baffles and one without. The primary focus is to analyze fuel distribution within the intake port region during vehicle acceleration and deceleration maneuvers. The simulated scenario mimics a realistic driving situation. The vehicle accelerates from 0 km/h to 60 km/h over 10 s, followed by a 3-s braking period to reach a complete stop (0 km/h) at the 13-s mark. The simulation then observes the fuel behavior within the tank for an addi-tional 7 s while the vehicle remains stationary. Results reveal significant differences in fuel behavior between baffled and unbaffled tanks. In the absence of baffles, the sloshing motion is substantial, leading to a complete depletion of fuel in the intake port region for a duration of 3 s during both the acceleration and deceleration phases (between 10 and 13 s). Compared to a standard tank, the presence of baffles significantly reduced the sloshing amplitude by approximately 70%. Furthermore, baffles led to a 50% decrease in pressure variations on the tank walls. Temporary fuel starvation can negatively impact engine performance and combustion efficiency. Conversely, the presence of baffles within the tank effectively mitigates sloshing and ensures continuous fuel presence at the intake port the entire simulation. This suggests that baffles play a crucial role in maintaining a stable and consistent fuel supply to the engine, even during dynamic vehicle maneuvers.

A Deep Insight into the Micro-Mechanical Properties of Mortar through a Multi-Phase Model

This study investigates the micro-mechanical behavior of mortar under uniaxial compression using a three-phase model in PFC3D. By simulating mortar as a composite of cement, sand, and the interfacial transition zone (ITZ), the research examines the impact of particle size on stress–strain behavior, crack propagation, porosity distribution, contact forces, and energy transformation. The simulations reveal that reducing sand particle size from 1–2 mm to 0.25–0.5 mm leads to a significant increase in uniaxial compressive strength, with peak strength values rising from 65.3 MPa to 89.6 MPa. The elastic modulus similarly improves by approximately 20% as particle size decreases. The study also finds that tensile cracks dominate failure, accounting for over 95% of total cracks, with their onset occurring at lower strains as the particle size is reduced. Porosity analysis shows that smaller particles result in a more uniform distribution, with the final porosity at peak strength ranging between 0.26 and 0.29, compared to 0.22 to 0.31 for larger particles. Additionally, energy dissipation patterns reveal that as particle size decreases, the boundary energy transformation into strain energy becomes more efficient, with a 15% increase in strain energy storage observed. These findings provide critical insights into optimizing mortar microstructure for enhanced mechanical performance in construction applications.

Experimental study on microscopic production characteristics and influencing factors during dynamic imbibition of shale reservoir with online NMR and fractal theory

Dynamic imbibition and displacement between the matrix and fractures in shale reservoirs can significantly enhance oil recovery (EOR) following initial depletion. However, the microscopic production characteristics and seepage mechanisms at different pore scales during the dynamic imbibition process remain incompletely understood. In this study, we established an online physical simulation experiment method that combines dynamic displacement and imbibition based on nuclear magnetic resonance (NMR) and fractal theory, and a series of online NMR water flooding dynamic imbibition experiments were conducted. Through real-time dynamic monitoring of multiphase flow and migration behavior of crude oil in each stage of dynamic imbibition, the microscopic production characteristics and influencing factors were quantitatively studied from the recovery and residual oil saturation field distribution of different scale pores. Additionally, we developed a novel two-dimensional (2-D) NMR interpretation model to investigate the dynamic development characteristics of shale oil injection-imbibition-soaking-production integration, and the multiphase and multi-scale dynamic imbibition crude oil migration models were discussed. The results show that shale oil occurrence pores can be categorized into two types based on the corresponding production mode (imbibition + displacement). The water flooding dynamic imbibition process in shale reservoirs unfolds in three stages: strong displacement and weak imbibition stage characterized by the rapid production of large pores and fractures under displacement action; weak displacement and strong imbibition stage involving the slow production of small pores under reverse imbibition; and dynamic equilibrium stage characterized by weak displacement and weak imbibition. When viewing the entire water flooding dynamic imbibition process as an organism, it becomes imperative to maximize the recovery of large pores while ensuring the recovery degree of small pores. High permeability contributes to better pore throat connectivity and a greater imbibition and displacement production degree. The contribution of the.two production modes to the recovery of small and large pores increased by 4.67 % and 3.17 %, respectively. A negative correlation was observed between high displacement pressure and imbibition recovery, yet it is conducive to the contribution of displacement to total recovery. Notably, fractures can effectively reduce oil-water seepage resistance, and increase the contribution of displacement to recovery by 21.65 %. Finally.a positive correlation was noted between increased imbibition amount and free oil recovery, while residual oil gradually shifted towards adsorbed and organic matter-dominated forms, leading to decreased recoverability. Effectively utilizing the bridge flow conductivity of fractures, fluid imbibition displacement, and carrying effect is crucial for achieving optimal EOR. The findings provide theoretical support for clarifying the interaction between matrix-fracture imbibition and displacement and for the efficient development of shale oil.

Intercellular friction and motility drive orientational order in cell monolayers

Spatiotemporal patterns in multicellular systems are important to understanding tissue dynamics, for instance, during embryonic development and disease. Here, we use a multiphase field model to study numerically the behavior of a near-confluent monolayer of deformable cells with intercellular friction. Varying friction and cell motility drives a solid-liquid transition, and near the transition boundary, we find the emergence of local nematic order of cell deformation driven by shear-aligning cellular flows. Intercellular friction contributes to the monolayer's viscosity, which significantly increases the spatial correlation in the flow and, concomitantly, the extent of nematic order. We also show that local hexatic and nematic order are tightly coupled and propose a mechanical-geometric model for the colocalization of [Formula: see text] nematic defects and 5-7 disclination pairs, which are the structural defects in the hexatic phase. Such topological defects coincide with regions of high cell-cell overlap, suggesting that they may mediate cellular extrusion from the monolayer, as found experimentally. Our results delineate a mechanical basis for the recent observation of nematic and hexatic order in multicellular collectives in experiments and simulations and pinpoint a generic pathway to couple topological and physical effects in these systems.