Numerical Simulation Of Two-phase Flow Research Articles

A modified Flux Corrected Transport method coupled with the MPFA-H formulation for the numerical simulation of two-phase flows in petroleum reservoirs using 2D unstructured meshes

A modified Flux Corrected Transport method coupled with the MPFA-H formulation for the numerical simulation of two-phase flows in petroleum reservoirs using 2D unstructured meshes

Three-dimensional numerical simulation of two-phase flow in a proton exchange membrane electrolysis cell and study of the effect of flow channel depth

Abstract The flow channel play a critical role in water-gas transfer within an electrolysis cell, directly impacting its mass and heat transfer capacity. While most studies concentrate on the overall shape and structure of the flow channel, limited attention has been given to its dimensions. This paper investigates the influence of various operational conditions and changes in flow channel depth on the electrolytic cell using a three-dimensional numerical model of PEMEC. Results indicate that higher temperatures enhance electrolysis cell performance, whereas the impact of water inlet velocity on the polarization curve is insignificant. Under constant inlet velocity, increasing the depth of the flow channel improves mass and heat transfer as well as electrolysis performance, whereas, under constant water flow rate, changes in inlet velocity have a greater effect than alterations in flow channel depth.

Numerical simulation of twophase flows on the base of phase-field method

Numerical simulation of twophase flows on the base of phase-field method

A Novel Connection Element Method for Multiscale Numerical Simulation of Two-Phase Flow in Fractured Reservoirs

Summary This paper presents a novel approach to the numerical simulation of fractured reservoirs, called the connection element method (CEM), which differs from traditional grid-based methods. The reservoir computational domain is discretized into a series of nodes, and a system of connection elements is constructed based on the given connection lengths and angles. The pressure diffusion term is approximated using generalized finite difference theory. Meanwhile, the transmissibility and volume of the connection elements are determined, and pressure equations are solved discretely to obtain pressure at nodes to approximate the upstream flux along connection elements. Then, we solve the transport equation to obtain oil saturation profiles with low numerical diffusion, utilizing the discontinuous Galerkin (DG) method. Moreover, the flow path tracking algorithm is introduced to quantify the flow allocation factors between wells. In all, the pressure equation can be solved at a global coarse-scale point cloud and the saturation equation is calculated at a local fine-scale connection element. In other words, CEM is of multiscale characteristics relatively. Finally, several numerical examples are implemented to demonstrate that CEM can achieve a relatively better balance between computational accuracy and efficiency compared with embedded discrete fracture modeling (EDFM). Furthermore, CEM adopts flexible meshless nodes instead of grids with strong topology, making it more practical to handle complex reservoir geometry such as fractured reservoirs.

A horizontal refined piecewise curve interface reconstruction (HOPCIR) algorithm for reconstructing the vapor-liquid interface

The vapor-liquid interface can be characterized as a circle or sphere affected by surface tension. However, linearization or planarization processing is commonly employed to simplify the reconstruction of the vapor-liquid interface within a grid cell, introducing errors in numerical simulations of two-phase flow. Therefore, this paper proposes a straightforward and accurate Horizontal Refined Piecewise Curve Interface Reconstruction (HOPCIR) algorithm to reconstruct the curve vapor-liquid interface for the two-dimensional structured grid. In this method, a standardized circle segment is employed to represent the vapor-liquid interface segment within each mixed grid cell, uniquely defined by its radius and center. The radius of this circle is determined by the curvature of the interface segment, and an iterative procedure is employed to calculate the circle's center using the known fluid volume fraction and initial interface obtained by linear reconstruction. Another integral aspect of the HOPCIR algorithm involves solving the reconstructed distance function to enhance the accuracy of curve reconstruction. Comparative analysis with the coupled volume-of-fluid and level set (VOSET) method demonstrates the superior performance of the HOPCIR algorithm in reconstructing vapor-liquid interfaces and solving the reconstructed distance function, interface curvature, surface tension, and fluid volume fraction.

Numerical Simulation of Solid-Liquid Two-Phase Flow in Pump

Abstract This paper is based on EDEM-FLUENT coupling calculation, the solid-liquid two-phase flow at pump is analyzed. Three kinds of solid phase volume concentration and three solid phase particle diameters are given respectively, and the solid-liquid two-phase flow numerical simulation of the internal flow field of the pump is carried out. The position distribution of solid particles in the flow field and the change of particle average velocity with time and the distribution of particle velocity are analyzed. The results show that the inlet of the runner and the pressure surface of the blade are the concentrated distribution areas of particles. With the increase in particle concentration, the particle distribution at the outlet of the volute is more uniform. The average velocity of particles at different particle concentrations varies similarly with time, but the average velocity of particles increases with the increase of concentration. With the increase in particle size, the average velocity of particles decreases, but the velocity value with the largest proportion of particles becomes larger.

Multiphase flow simulation in hybrid porous structure

Recent research has primarily focused on creating biporous and hybrid porous structures with multiple pore sizes and length scales to optimize capillary pressure and permeability. Despite numerous experimental investigations on biporous and hybrid media, there is a noticeable absence of numerical simulations that explore the multiphase flow within these media. Therefore, the present study aims to conduct a pore-scale numerical simulation of two-phase flow in a biporous structure. The biporous structure is proposed by arranging clusters of solid particles in a staggered regular pattern, with each cluster consisting of closely packed particles. The dimensions and characteristics of the simulated structure are based on previous experimental literature on biporous and hybrid media. A monoporous structure simulation is also included for comparison with biporous results. ANSYS Fluent is utilized to carry out the numerical simulations of capillary pumping flow. The simulation results indicate that the permeability and average capillary pressure of the biporous media are four times and over one and a half times higher, respectively, compared to those of the monoporous media. The presence of smaller pathways within each cluster of a biporous and hybrid porous media enhances the capillary effect in comparison to conventional monoporous structures. Additionally, the larger pores between the clusters contribute to a higher permeability of the hybrid porous structure. As a result, the combined effect of increased capillary action and higher permeability leads to improved performance of the hybrid porous structure. Overall, the proposed simplified biporous geometry accurately models fluid flow in real, complex biporous and hybrid structures.

Effect of different particle sizes on combustion characteristics of DCR engines

The ramjet engine has undergone rapid development in recent decades, and the dual combustion chamber ramjet (DCR) engine was proposed in the last century. Boron, with its high volumetric and gravimetric heating values, is one of the most attractive fuel additives for ramjet engines. However, due to the problem of low combustion efficiency, boron is difficult to achieve high efficiency combustion in practical applications. In order to investigate the combustion characteristics of boron-containing gas solid phase components in DCR engines, the Realizable k-ε model, finite rate/vortex dissipation model and boron particle King model ignition combustion calculation program were written. A three-dimensional full-scale two-phase flow numerical simulation was carried out in the combustion chamber of the DCR engine to calculate the effects of different particle sizes on the combustion characteristics. Through the analysis of the simulation results, the particle size affects the ignition time of boron particles and is positively correlated with the combustion efficiency, but with a non-linear growth. A smaller particle size can promote the ignition of boron particles, improve the solid phase combustion efficiency and achieve efficient combustion.

Hybrid Mimetic Finite Difference and Streamline Methods for Numerical Simulation of Two-phase Flow in Fractured Reservoirs

In this work, we present a novel numerical formulation for efficiently modeling two-phase flow in fractured reservoirs. The novel formulation is developed by hybridizing mimetic finite difference and streamline (MFD-SL) methods, in which mimetic finite difference (MFD) is employed to discretize the pressure equation, and the streamline (SL) method is adopted to solve the saturation equation along 1D streamlines. The hybrid formulation is implemented on discrete fracture model (DFM) and is operated in an IMPES-like manner. A simple and practical streamline tracing method is developed on 2D triangular and 3D tetrahedral grids that are commonly implemented in the DFM framework. We benchmark the hybrid MFD-SL formulation with others using various cases with different complexity. Results show the proposed approach could achieve promising results yet with lower computation costs compared to other classical formulations. These achievements benefit from utilizing streamline tracing, which significantly alleviates the numerical diffusion error and improves the computation efficiency. This work, for the first time, incorporates hybrid MFD-SL formulation into DFM in case of triangular and tetrahedral grids and has great potential to be deployed on reservoir-scale simulation workflow.

MODELING OF TWO-PHASE GAS-LIQUID SLUG FLOWS IN MICROCHANNELS

Even though numerical simulation of two-phase flows in microchannels has been attempted by many investigators, most efforts seem to have failed in correctly capturing the flow physics, especially the slug-flow regime characteristics. The presence of a thin liquid film in the order of 10 μm around the bubble (sometimes called gas pocket or gas slug) may be a contributing factor to the above difficulty. Typically, liquid films have a significant effect on the flow field. Thus, there is a strong motivation to employ numerical simulation methods to avoid some of the experimental difficulties. In this paper, the characteristics of two-phase slug flows in microchannels are calculated with the help of the volume-of-fluid (VOF) method. Formation of the slugs for different superficial velocities, capillary numbers, and gas volume fractions are investigated. The minimum mesh resolution required to capture the liquid film surrounding the gas bubble is reported employing a dynamic mesh adaptation methodology with interface tracking. Results are shown to be in good agreement with experimental data and empirical correlations.

Evolution of air-entraining vortices in inclined intake pumping stations under low sump water depth condition

The air-entraining vortices may appear in a pump sump when the pumping station operates at a low water depth, which will induce undesirable phenomena such as cavitation and vibration. In this paper, the evolution process of air-entraining vortices is studied in detail based on the volume of fluid (VOF) two-phase flow numerical simulation method, to clarify its hydraulic characteristics and influence. The results show that the water-air interface in the sump varying periodically with time under a low water depth consists of four stages, that is, slow rise, fast rise, continuous stability and reduction. The shape of the air-entraining vortices shows a periodic evolution under the interference of water surface fluctuations, from the surface dimple to the full air core to intake, then to the vortex pulling air bubbles to intake, and finally back to the surface dimple. The inhaled air volume fraction in the suction pipe changes with the evolution of the air-entraining vortices. In addition, the average angle of velocity distribution and the average swirl angle are analyzed in depth to improve the understanding of flow pattern caused by the complicated and diversified inhaled air.

A New Fully Implicit Two-Phase Pore-Network Model by Utilizing Regularization Strategies

In this paper, we address the expensive computational cost resulting from limited time-step sizes during numerical simulations of two-phase flow in porous media using dynamic pore-network models. To overcome this issue, we propose a numerical method for dynamic pore-network models using a fully implicit approach. The proposed method introduces a regularization strategy considering the historical fluid configuration at the pore throat, which smooths the discontinuities in local conductivity caused by invasion and snap-off events. The results demonstrate the superiority of the proposed method in terms of accuracy, efficiency and consistency in comparison with other numerical schemes. With similar computational cost, determined by time-step sizes and number of Newton iterations, the developed method in this work yields more accurate results compared to similar schemes presented in the literature. Additionally, our results highlight the enhanced robustness of the our scheme, as it exhibits reduced sensitivity to variations in time-step sizes.

Parallel Immersed Boundary Method for Two-Phase Flows on DCU Clusters

The immersed boundary method (IBM) is widely used in simulating multiphase flows. DCU (Deep Computing Unit) acceleration device is a kind of GPU-like device, which is developed by GPU technology authorised by AMD. To achieve an efficient numerical simulation of two-phase flows, we develop a parallel DCU-based immersed boundary method using the MPI+HIP programming model. To solve the slow convergence problem caused by domain partitioning in multigrid methods, a coarse grid aggregation (CGA) technique is effectively employed. We adopt a nonblocking communication approach with HIP streams to overlap computation and communication. To validate the proposed method running on DCU clusters, we conducted two numerical experiments of droplet deformation in shear flow and the rising bubble. Performance tests show that a speedup of 181 times more than the CPU version can be achieved with 32 DCUs in a 1024 × 512 × 512 mesh grid.

Development of an efficient numerical model for two-phase flows in air-lift pumps and its application to deep-sea mining

Air-lift pump system has been selected as a potential application to convey the Rare-Earth mud in deep-sea mining processes due to the superior reliability and schematic simplicity. It is a major focus of current research to study the behavior and mechanism of the two-phase flow. Based on the drift flux model and modified Akawa pressure drop equation, mathematical model controlling the numerical simulation of two-phase flow within air-lift pump system is proposed and constructed. Comparison with experimental data concerning steady and unsteady two-phase flows in vertical pipes shows the high precision of the model. Combing with the robustness test results, it can be found that the present model can accurately predict the maximum flow rate of the two-phase flow at the outlet of the gas lift pump, as well as the average gas and liquid flow rates of the two-phase flow at the outlet in both steady and unsteady states. On this basis, several operation laws of the deep-sea mining airlift pump were studied. The relationship between input and output in the mining process is established and the output of the gas lift pump system is predicted. It is found that changing the position of the injected gas, the time for the two-phase flow in the vertical pipe to reach dynamic equilibrium varies equiprimordially. And changing the maximum amount of gas injected, the time required to reach dynamic equilibrium shows a symmetric relationship with the volume fraction after dynamic equilibrium. A series of laws closely related to the prediction of rare earth mud at the outlet of gas-lift pumps in deep-sea mining are investigated to be proposed for subsequent studies.

Drag force modification model for turbulent suspended-load sediment solid–liquid two-phase flow

The calculation accuracy of a solid–liquid two-phase flow numerical simulation is related directly to the reliability of the results obtained. The interphase drag force significantly affects the calculation results of the solid concentration distribution of suspended-load sediment solid–liquid two-phase flow. However, the conventional Wen–Yu drag force model is obtained by adding solid concentration to the standard drag force coefficient curves. The model does not consider the influence of turbulence, which is a comprehensive reflection of particle inertia and liquid turbulence intensity. To improve the calculation accuracy of the Wen–Yu model, the particle inertia and turbulence intensity factors are introduced to express the comprehensive influence of the particle inertia and liquid turbulent intensity on the drag force coefficient for the suspended-load sediment solid–liquid two-phase flow. The turbulence modification function preliminary expression is determined and further modified to improve the calculation accuracy for a particle Reynolds number of less than 100 by combining experimental data and the least square method through experiments and theoretical research. Then, the final expression of the turbulence modification function is proposed to help modify the drag force coefficient of the Wen–Yu model, and finally establish the modified turbulence effect (MTE)-Wen–Yu drag force modification model. The calculations for the suspended-load sediment solid–liquid two-phase flow in the circular tubes show that the solid-phase concentration values calculated by the MTE-Wen–Yu drag force model are considerably closer to the experimental results than those obtained by the Wen–Yu drag force model in the suspended-load sediment solid–liquid two-phase flow calculation for different inlet velocities, inlet solid concentrations, and particle diameters. Hence, the calculation accuracy of the MTE-Wen–Yu model is higher than that of the Wen–Yu drag force model. The calculation precision of the solid-phase concentration distribution calculated using the MTE-Wen–Yu drag force model decreases with the increase in particle diameter owing to the high quality and large inertia of large particles. Therefore, it is more suitable for the numerical simulation of suspended-load sediment solid–liquid two-phase flow with a small particle diameter.

Integrated modeling of heat transfer, shear rate, and viscosity for simulation-based characterization of polymer coalescence during material extrusion

The material extrusion process (MEX), also known as the fused filament fabrication process, has attracted attention in the manufacturing industry. A major obstacle to further application of the technology is the lack of mechanical strength due to the weak interlayer strength and poor coalescence between the adjacent beads. Understanding the effect of printing parameters on the coalescence of the adjacent beads is a step toward the improvement of the process. In this study, a novel two-phase flow numerical simulation approach coupled with heat transfer simulation has been applied to the high-viscosity polymers to determine the coalescence in the MEX process. The influence of printing temperature, substrate temperature, and the temperature of the printing chamber, as well as material deposition strategy (unidirectional and bidirectional) on the coalescence of the beads, has been investigated by numerical simulation and validated by experimental study. The modeling approach is applied to Glycerol, Polyether ether ketone (PEEK) and Polylactic acid (PLA). The results show that increasing temperature points (substrate temperature, chamber temperature, and printing temperature), increase the coalescence between the beads in the MEX process. The heat transfer model reveals that the cooling rate of the deposited bead in the MEX process is relatively high, and hence, the time window for reaching the coalescence between beads/layers is short. The heat transfer model also indicates that deposition of the further layers and beads does not influence the coalescence. The coalescence in the bidirectional deposition is higher compared to the unidirectional all conditions remaining similar. Unidirectional deposition leads to a uniform coalescence between the beads. However, the coalescence is not uniform for bidirectional deposition. The main novelty of this research is to simultaneously model heat transfer, shear rate and coalescence for numerical simulation to study the effect of printing parameters on the coalescence in the MEX process. Since the modeling of coalescence is time-consuming, two empirical equations based on obtained results have been proposed to predict the coalescence for PLA and PEEK separately.

Numerical simulation of two-phase flow in gas diffusion layer and gas channel of proton exchange membrane fuel cells

Liquid water within the cathode Gas Diffusion Layer (GDL) and Gas Channel (GC) of Proton Exchange Membrane Fuel Cells (PEMFCs) is strongly coupled to gas transport properties, thereby affecting the electrochemical conversion rates. In this study, the GDL and GC regions are utilized as the simulation domain, which differs from previous studies that only focused on any one of them. A Volume of Fluid (VOF) method is adopted to numerically investigate the two-phase flow (gas and liquid) behavior, e.g., water transport pattern evolution, water coverage ratio as well as local and total water saturation. To obtain GDL geometries, an in-house geometry-based method is developed for GDL reconstruction. Furthermore, to study the effect of GDL carbon fiber diameter, the same procedure is used to reconstruct three GDL structures by varying the carbon fiber diameter but keeping the porosity and geometric dimensions constant. The wall wettability is introduced with static contact angles at carbon fiber surfaces and channel walls. The results show that the GDL fiber microstructure has a significant impact on the two-phase flow patterns in the cathode field. Different stages of two-phase flow pattern evolution in both cathode domains are observed. The liquid water in the GDL experiences water invasion, spreading, and rising, followed by the droplet breakthrough in the GDL/GC interface. In the GC, the water droplets randomly experience accumulation, combination, attachment, and detachment. Due to the difference in surface wettability, the water coverage of the GDL/GC interface is smaller than that of the channel side and top walls. It is also found that the water saturation inside the GDL stabilizes after the water breakthrough, while local water saturation at the interface keeps irregular oscillations. Last but not the least, a water saturation balance requirement between the GDL and GC is observed. In terms of varying fiber diameter, a larger fiber diameter would result in less water saturation in the GDL but more water in the GC, in addition to faster water movement throughout the total domain.

A study on droplet group evaporation modeling based on interface resolved numerical simulations of two-phase flow

Large-scale numerical analyses of the evaporation of groups of 640 droplets and 2,964 droplets were conducted by the interface-resolved simulation method, and the effect of mutual droplet interference on the evaporation rate of droplets in groups was modeled. The interference effect reduces the evaporation rate of each droplet due to the increase in its surrounding fuel concentration caused by the evaporation of neighboring droplets. The evaporation rate interference coefficient, which is the ratio of the evaporation coefficient of each droplet in a group to that of a single droplet without interference, was modeled using three parameters: the distance between the droplets, the size of the droplet interfering with an object droplet, and the evaporation state of the interfering droplet. A new droplet evaporation rate parameter containing these model parameters was proposed, and it was confirmed that the proposed parameter properly models the evaporation rate interference coefficient calculated using the droplet group evaporation numerical analysis results. In addition, the accuracy of the model was improved by including a further parameter to express the positional relationship of a droplet within a group.

Numerical Simulation of Two-Phase Flow in Glutenite Reservoirs for Optimized Deployment in Horizontal Wells

It is known that the pore media characteristics of glutenite reservoirs are different from those of conventional sandstone reservoirs. Low reservoir permeability and naturally developed microfractures make water injection in this kind of reservoir very difficult. In this study, new exploitation methods are explored. Using a real glutenite reservoir as a basis, a three-dimensional fine geological model is elaborated. Then, combining the model with reservoir performance information, and through a historical fitting analysis, the saturation abundance distribution of remaining oil in the reservoir is determined. It is shown that, using this information, predictions can be made about whether the considered reservoir is suitable for horizontal well fracturing or not. The direction, well length, well spacing and productivity of horizontal well are also obtained.

Numerical simulation of two-phase flow in a microchannel for evaluating liquid film thickness and its Reynolds number dependency

Numerical simulation of two-phase flow in a microchannel for evaluating liquid film thickness and its Reynolds number dependency