Numerical Simulation Of Two-phase Flow Research Articles

Research Progress on Numerical Simulation of Two-phase Flow in the Gas-solid Fluidized Bed

It is difficult to accurately measure the parameters of solid particles in the experiment of the gas-solid fluidized bed. The numerical simulation plays an important role to accurately describe flow characteristics in the fluidized bed. Combined with the research work of the research group, this paper analyzes the application of numerical simulation of fluidized bed from the aspects of gas-solid coupling algorithm, drag model, flow characteristics, and reaction characteristics based on the previous studies. The specificity improvement of the gas-solid coupling algorithm and the regional application of the drag model is the trend of the recent development of numerical simulation. Previous studies mainly focus on the gas-solid two-phase flow field characteristics in the traditional fluidized bed, but few on the complex flow characteristics such as gas-solid reverse flow and the coupling with reaction characteristics. It is of great significance for designing a novel fluidized bed reactor to realize gas-solid continuous reaction to establish and improve the numerical simulation method of gas-solid non-catalytic reaction.

Numerical investigation of immiscible Liquid-Liquid displacement in Hele-Shaw cell

In the present work, a numerical simulation has been performed on the immiscible liquid–liquid displacement flow in two- dimensional rectilinear Hele-Shaw cell (HSC) by using ANSYS FLUENT commercial software. The volume of fluid (VOF) model has been used to track the interface of immiscible liquids in the displacement flow process. A finger shape instability records at the oil–water interface when a large viscous liquid oil is displaced by lower viscous liquid water from the oil-saturated Hele-Shaw cell. This finger shape interfacial instability is called viscous fingering. The viscosity ratio (ratio of the viscosity of displacing and displaced liquids) of two-phase flow is less than unity then unstable displacement occurs and results in finger shape instability appears at the interface. The numerical simulation of two-phase flow has been performed by using the pressure base solver and transient model. The present work aims to capture the propagation of a finger shape instability at the oil–water interface and calculate the sweep efficiency by image processing. We observed that water displaces approximately 72.42% of oil from the entire oil-saturated HSC and sweep efficiency gradually increases with time in the displacement process.

A Qualitative Numerical Study on Catalytic Hydrogenation of Nitrobenzene in Gas-Liquid Taylor Flow with Detailed Reaction Mechanism

While the number of computational studies considering two-phase flows in microfluidic systems with or without mass transfer is increasing, numerical studies incorporating chemical reactions are still rare. This study aims to simulate the catalytic hydrogenation of nitrobenzene in gas-liquid Taylor flow by combining interface-resolving numerical simulations of two-phase flow and mass transfer by a volume-of-fluid method with detailed modeling of the heterogeneous chemical reaction by software package DETCHEMTM. Practically relevant physical properties are utilized for hydrodynamic and mass transfer simulations in combination with a preliminary reaction mechanism based on density functional theory. Simulations of mass transfer are conducted using a predetermined velocity field and Taylor bubble shape. At the beginning of the simulation when liquid nitrobenzene is not saturated by hydrogen, axial profiles of surface species concentrations and reaction rates show local variations. As hydrogen dissolves in nitrobenzene, the concentration profiles of surface species at the wall become uniform, eventually reaching an equilibrium state. Neglecting the local variation in a short initial period will allow further simplification of modeling surface reactions within a Taylor flow.

Large-Scale Coupling Numerical Simulation of Two-Phase Flow and Electrochemical Phenomena in Alkaline Water Electrolysis

The alkaline water electrolysis is one of the methods of large-scale hydrogen production, and it is required to improve its efficiency. Experimental approach and numerical studies have been conducted to improve the efficiency [1,2]. Abdelouahed et al. [3] confirmed that bubbles strongly influence the flow field pattern and mix the local electrolyte near the electrodes. Ehrl et al. [4] conducted a numerical simulation of electrochemical systems with natural convection and solved both multi-ion transportation and flow in the cell. In these studies, macroscopic (mm scale) hydrodynamical behavior have been discussed, however, the size of the bubbles in water electrolysis can be micro scale and microscale flow can be induced. We have been studied about the microscale hydrodynamical effect on the alkaline water electrolysis with two-phase flow, electrochemical, and electromagnetic coupling numerical simulations. In our previous studies [1,2], numerical simulations of flow around the aligned bubbles with a cyclic boundary condition are conducted and it is revealed that the rising bubbles suppress the cell overpotential and this suppression is enhanced by a bubble atomization, however, there is a strong limitation to the bubble movement and it had been difficult to discuss the bubble-bubble interaction and the influence of that on the efficiency of the alkaline water electrolysis cell. From the background mentioned above, in this study, large-scale coupling numerical simulations are conducted to elucidate the influence of the bubble-bubble interactions on the cell overpotential. Strength of the interaction depends on dispersibility of bubbles. So, we also discuss the influence of the dispersibility of multiple bubbles on the cell overpotential.In this study, electrochemical, two-phase flow, electromagnetic field coupling numerical simulation are conducted with the same procedure as previous studies [1,2]. The analysis area is expanded to calculate the bubble-bubble interaction and the number of grids is 16 million. Graphical Processing Unit (GPU) are used in this calculation for Large-scale parallel analysis to realize this simulation. The average applied current density is 400 mA/cm2, the bubble size of oxygen bubbles is 500μm and four bubbles are set close to the anode at initial condition. The numerical simulations are conducted with changing the dispersibility from 0.25 to 0.92. Dispersibility is 1 when bubbles are equally spaced and is 0 when bubbles are concentrated and in touched.Figure 1 shows the influence of the dispersibility (D) on the cell overpotential. From D = 0.25 to 0.43, the overpotential is almost decreased with the increase in D, and it increased with the increase in D from D = 0.43 to 0.92. Fig.2 shows concentration distribution, iso-surface (1.7 mol/L) and bubbles position with dispersibility of (a) D = 0.25, (b) D = 0.43 and (c) D = 0.92. In the case of low dispersibility (D = 0.25, Fig.2 (a)), the overpotential is high and some bubbles are combined and remain close to the anode. These bubbles close to the anode, make shielding effect and increase the ohmic loss. The anodic activation overpotential is also high because fewer bubbles reduce the flow and decrease the concentration near the anode. With the increasing in D, the overpotential is suppressed (D = 0.43, Fig.2 (b)). In this case of optimum dispersibility, some bubbles locate far from the anode. This is because, the upper bubble leaves from the anode because of the lift force against the anode [5] and induces repulsive force to the lower bubble [6]. This upper bubble far from the anode, reduces shielding effect and suppresses the ohmic loss. The anodic activation overpotential is also suppressed because the interaction between the bubbles enhance the flow which facilitate the ion transportation and increase the concentration near the anode. In the case of high dispersibility (D = 0.92, Fig.2 (c)), many bubbles remain close to the anode. These bubbles make shielding effect and increase the ohmic loss. The anodic activation overpotential is also increased because there is little interaction between bubbles to generate strong flow and the concentration near the anode are decreased. In conclusion, this study reveals that the interaction between bubbles affects the cell overpotential, and bubbles in optimum dispersibility, the cell overpotential can be suppressed. Acknowledgement This study is partially supported by Nissin Sugar Found and Japan High Performance Computing and Networking plus Large-scale Data Analyzing and Information Systems. Figure 1

Design of coupled finite volume schemes minimizing the grid orientation effect in reservoir simulation

In this paper, we propose an analysis method for the so-called grid orientation effect (GOE) in the numerical simulation of two-phase flows in porous media. The GOE, which occurs when using coupled finite volume schemes on structured grids, is well known to engineers. Several attempts, most of which are of empirical nature, have been put forward in order to alleviate this undesirable phenomenon. Here, our approach relies on a more rigorous notion of angular error for all directions, which in turn enables us —via integration and minimization— to single out the “least anisotropic” scheme within a given family of schemes depending on some tuning parameter(s). Numerical test problems testify to the improvement brought by the new construction.

Large-Scale Coupling Numerical Simulation of Two-Phase Flow and Electrochemical Phenomena in Alkaline Water Electrolysis

The alkaline water electrolysis is one of large-scale hydrogen production methods. While a lot of experiments and numerical simulations have been conducted to elucidate the internal phenomena and to improve the efficiency of the alkaline water electrolysis, there still is room for improvement in the efficiency. In this study, large-scale coupling numerical simulations of two-phase flow and electrochemical phenomena are conducted to elucidate the influence of the bubble-bubble interactions on ion transport and cell overpotential. The results showed that the interaction between bubbles affects cell overpotential, and cell overpotential can be suppressed when bubbles are optimally dispersed.

Numerical Simulation of Two-Phase Flows in Heterogeneous Porous Media

In this work,we present three-dimensional numerical simulations of water-oil flow in porous media in order to analyze the influence of the heterogeneities in the porosity and permeability fields and, mainly, their relationships upon the phenomenon known in the literature as viscous fingering. For this, typical scenarios of heterogeneous reservoirs submitted to water injection (secondary recovery method) are considered. The results show that the porosity heterogeneities have a markable influence in the flow behavior when the permeability is closely related with porosity, for example, by the Kozeny-Carman (KC) relation.This kind of positive relation leads to a larger oil recovery, as the areas of high permeability(higher flow velocities) are associated with areas of high porosity (higher volume of pores), causing a delay in the breakthrough time. On the other hand, when both fields (porosity and permeability) are heterogeneous but independent of each other the influence of the porosity heterogeneities is smaller and may be negligible.

Numerical Simulation of Two-Phase Flows in Heterogeneous Porous Media

In this work,we present three-dimensional numerical simulations of water-oil flow in porous media in order to analyze the influence of the heterogeneities in the porosity and permeability fields and, mainly, their relationships upon the phenomenon known in the literature as viscous fingering. For this, typical scenarios of heterogeneous reservoirs submitted to water injection (secondary recovery method) are considered. The results show that the porosity heterogeneities have a markable influence in the flow behavior when the permeability is closely related with porosity, for example, by the Kozeny-Carman (KC) relation.This kind of positive relation leads to a larger oil recovery, as the areas of high permeability(higher flow velocities) are associated with areas of high porosity (higher volume of pores), causing a delay in the breakthrough time. On the other hand, when both fields (porosity and permeability) are heterogeneous but independent of each other the influence of the porosity heterogeneities is smaller and may be negligible.

Overvoltage Suppression Mechanism of Alkaline Water Electrolysis by Magnetic Field with Two-phase Flow and Magneto Hydro Dynamic Coupling Numerical Simulation Around a Bubble

Overvoltage Suppression Mechanism of Alkaline Water Electrolysis by Magnetic Field with Two-phase Flow and Magneto Hydro Dynamic Coupling Numerical Simulation Around a Bubble

Numerical simulation of two-phase flow within sudden expansion in horizontal channel pressure and velocity distribution

In this paper, we will study the flow of two immiscible fluids (air/water) through a sudden expansion in a horizontal channel. The first part of the paper will be a detailed bibliography study of sudden expansion problems followed by a mathematical and numerical study where detailed equations and numerical methods used for the numerical simulation are presented. The second part of the paper represents the numerical results obtained. First, we will validate our numerical model with the experimental results obtained by Chalfi and Ghiaasiaan (Int J Multiph Flow 34(1):2–12, 2008. https://doi.org/10.1016/j.ijmultiphaseflow.2007.09.004). The validation will be for the pressure distribution in the channel and the pressure jump over the sudden expansion. A comparison will be also done with the experimental results from Chalfi and Ghiaasiaan (2008) and the theoretical model from Armand-type void-quality expression for the pressure with different Reynolds numbers. After that, a numerical study will be done with a different ratio of the same geometry, pressure and velocity parameter will be studied and the jump over these variables is captured at the sudden expansion. The numerical part is done with the FEniCS platform which is a powerful finite-element computational open-source scientific platform.

Pore-scale investigation of the displacement fluid mechanics during two-phase flows in natural porous media under the dominance of capillary forces

This paper presents the results of numerical simulations of two-phase flows in porous media under capillary forces dominance. For modeling of immiscible two-phase flow, the lattice Boltzmann equations with multi relaxation time operator were applied, and the interface phenomena was described with the color-gradient method. The objective of study is to establish direct links between quantitative characteristics of the flow and invasion events, using high temporal resolution when detecting simulation results. This is one of the few works where Haines jumps (rapid invasion event which occurs at meniscus displacing from narrow pore throat to its wide body) are considered in three-dimensional natural pore space, but the focus is also on the displacement mechanics after jumps. It was revealed the sequence of pore scale events which can be considered as a period of drainage process: rapid invasion event during Haines jump; finish of jump and continuation of uniform invasion in current pore; switching of mobile interfaces and displacement in new region. The detected interface change, along with Haines jump, is another distinctive feature of the capillary forces action. The change of the mobile interfaces is manifested in step-like behavior of the front movement. It was obtained that statistical distributions of pressure drops during Haines jumps obey lognormal law. When investigating the flow rate and surface tension effect on the pressure drop statistics it was revealed that these parameters practically don’t affect on the statistical distribution and influence only on the magnitude of pressure drops and the number of individual Haines jumps.

Numerical simulation of two-phase flows in 2-D petroleum reservoirs using a very high-order CPR method coupled to the MPFA-D finite volume scheme

The focus of the present work is to model the two-phase flow of oil and water in 2-D anisotropic petroleum reservoirs using a novel appropriate combination of a non-orthodox cell-centered Multipoint Flux Approximation with a Diamond Stencil (MPFA-D) finite volume method to discretize the pressure equation coupled to the very high-resolution Correction Procedure via Reconstruction (CPR) scheme for the discretization of the saturation equation. To suppress numerical oscillations (under/overshoots) near shocks, that are typical in higher-order schemes, and to deliver high accuracy in smooth regions of the solution, a hierarchical Multidimensional Limiting Process (MLP) is used in the reconstruction stage. The integration in time is carried out using a third-order Runge–Kutta method. The coupling of the pressure-saturation set of equations is carried out using a classical Implicit Pressure Explicit Saturation (IMPES) procedure. To properly couple the MPFA-D method with the CPR formulation, it is necessary to obtain an adequate velocity reconstruction throughout the control volumes of the mesh. Because the cell-centered finite volume method naturally delivers fluxes across control surfaces of the primal grid, then, we use a reconstruction operator based on the lowest order Raviart–Thomas interpolation functions and the Piola transformation, to get the complete knowledge of the velocity field throughout the domain. Finally, some representative problems were solved to evaluate the accuracy, efficiency, and shock-capturing capabilities of our new numerical methodology.

Multiscale mixed methods for two-phase flows in high-contrast porous media

The Multiscale Robin Coupled Method (MRCM) is a domain decomposition procedure that has been developed to efficiently approximate velocity and pressure fields for single-phase flows in highly heterogeneous porous media. It generalizes other well-established multiscale domain decomposition mixed methods and it adds great flexibility to the choice of interface spaces as well as in the boundary conditions for subdomain coupling. We investigate the approximation of two phase flows in porous media using the MRCM to compute velocity fields. We consider an operator splitting strategy, where a scalar conservation law for the saturation of one of the phases and the velocity field are updated sequentially. We find that the coupling of nearest neighbor subdomains through the imposition of a continuous pressure (respectively, normal fluxes) is the best strategy to approximate two-phase flows in the presence of high (resp., low) permeability channels (resp., regions). A new adaptivity strategy for setting an algorithmic parameter of the MRCM, that controls the relative importance of Dirichlet and Neumann boundary conditions in the coupling of subdomains, is proposed and tested in challenging, high-contrast permeability fields. Our numerical simulations of two-phase flows show that by switching between existing multiscale procedures we can observe unprecedented accuracy, in that we produce better solutions for problems with high-contrast permeability coefficients when compared to solutions obtained with some standard multiscale mixed methods.

Numerical simulation of two-phase flow in 4x4 simulated bundle

An evaluation methodology of a thermal-hydraulics based on a mechanism in light water reactors (LWRs) is needed from a viewpoint of the safety analysis during normal operation and unanticipated transient such as under a severe accident. Currently, the evaluation of safety for the nuclear reactor has been implemented by a best estimate (BE) code and subchannel analysis code. These analysis codes contain models and empirical correlations. Therefore, the full-scale mock-up tests are needed to evaluate the reliability and validation of code. And the model and empirical correlation are allowed to be applied only in the range where the experiments were implemented. The large mock-up tests are once again needed in order to consider the new geometry and boundary conditions when the design of components is changed. Hence, the 3D detailed numerical simulation by the mechanistically based method is expected to be applied for the preliminary analysis to improve the design of fuel assemblies and evaluate the safety. This 3D detailed numerical simulation can reduce the large mock-up tests. The detailed numerical simulation method can provide much information relating to the two-phase flow such as the bubble size, its velocity, and detailed void distribution which, for example, are needed to predict the critical heat flux based on the mechanism. Moreover, JAEA is implementing the development of the nuclear-thermal-coupling code by using a detailed two-phase flow analysis code based on the VOF method like a JUPITER code. In this study, the numerical simulation of two-phase flow in the 4x4 bundle was examined by numerical simulation code JUPITER in order to examine the possibility of the JUPITER code for the large scale two-phase flow analysis. The simulation results are verified by the previous experimental data of two-phase flow.

Experiment and numerical simulation of two-phase flow in oxygen enriched side-blown furnace

Abstract Taking an oxygen enriched side-blown furnace as the prototype, a hydraulic model was established according to the similarity principle. The influence of three factors on the gas—liquid two-phase flow was analyzed, i.e. the airflow speed, the submerged depth and the downward angle of the nozzle. A numerical simulation of the hydraulic model was carried out trying to find the suitable turbulence model which can describe the side-blown two-phase flow correctly by comparing the simulation results with the experimental data. The experiment shows that the airflow speed has a great influence on the flow of the water. The submerged depth of the nozzle has a relatively smaller influence on the penetration depth and the surface fluctuation height in the liquid phase. When the nozzle is at a downward angle of 15°, the penetration depth and the surface fluctuation height are reduced. It is concluded that the numerical results with the realizable k–ɛ turbulence model are the closest to the experiment for the penetration depth, the surface fluctuation height and the bubble scale.

Investigation of influential factors on well temperature for gas-liquid two-phase flow in under-balanced drilling operation

Analysis of the drilling fluid temperature due to heat transfer of drilling fluid with the formation in under-balanced drilling operation is the main objective of this study. Gas-liquid two-phase flow model considering thermal interaction with the formation is used to numerically simulate a well with real dimensions. In the present study, the continuity, momentum, and energy equations are developed to compute the wellbore temperature profile. In this simulation, the effects of oil and gas production from the reservoir into the annulus and heat generated by viscous dissipation within the drilling fluid, heat generated by friction between the rotating drill string and the wellbore wall, and heat generated by the drill bit were included in the model. The results are validated with actual field data and also with two-phase flow model using the geothermal temperature gradient given in the literature. Comparisons of the present results show that two-phase flow numerical simulation with thermal consideration gives more accurate results compared to other models for the prediction of the bottom-hole pressure. Results show that the fluid temperature at the bottom-hole increases with increasing well depth, the flow rate of gas, and source terms consideration. Whereas the fluid temperature at the bottom-hole decreases with increasing liquid flow rate and specific heat of liquid and gas.

Investigation of slug-churn flow induced transient excitation forces at pipe bend

Numerical simulations of two-phase flow induced fluctuating forces at a pipe bend have been carried out to study the characteristics of multiphase flow induced vibration (FIV). The multiphase flow patterns and turbulence were modelled using the volume of fluid (VOF) method and the k−ϵ turbulence model respectively. Simulations of seventeen cases of slug and churn flows have been carried out showing the effects of superficial gas and superficial liquid velocities. The simulations results show good agreement of the volume fraction fluctuation frequencies of slug and churn flows with the reported experiment. In addition, the vibration characteristics of the excitation force have been accurately captured. The simulation results show that the predominant frequency of fluctuations of force decreases and the RMS of force fluctuation increases with the increase of superficial gas velocity. On the other hand, both predominant frequency and the RMS of force fluctuations increases with the increase of superficial liquid velocity. Increase of gas fraction narrows the range of frequency ranges, while increasing the liquid expands the frequency ranges of force fluctuations.

Three-Dimensional Numerical Coupling Simulation of Two-Phase Flow and Electrochemical Phenomena on Alkaline Water Electrolysis

Hydrogen is an essential energy carrier to ensure energy security. The alkaline water electrolysis is one of the methods of hydrogen production and large-scale hydrogen production can be achieved with this method. Since the energy efficiency on a present water electrolysis plant is only 60% [1], improving the efficiency is required for high energy efficiency hydrogen energy system. The energy loss in water electrolysis with high current density comes from a lack of the ion on the electrode, therefore promoting the ion transportation can improve the electrolysis efficiency. The reason of the decrease in the water electrolysis efficiency have been studied; Qian [2] showed generated gas bubbles sticking to the electrodes decrease effective surface area, and Jassen [3] revealed the presence of gas bubbles prevents ion transportation in the electrolyte. Whereas, Vogt [4] reported that mass transportation phenomena are classified into three types of convections induced by gas bubbles, which can encourage ion transportation. These results indicate the dynamics of bubbles play a significant role on the ion transportation and the efficiency. As the investigation with experiments have a limitation, numerical simulations have also been carried out. Mat [5] investigated an effect of gas evolution on a vertical electrochemical cell with two-phase flow model simulating void fraction in the cell. Hreiz [6] simulated two-phase flow induced by electrogenerated bubbles using the two-way momentum coupling Euler-Lagrange CFD approach. Nevertheless, there are only a few studies that dealt with both two-phase flow and electrochemical reaction. Furthermore, no previous study has analyzed an effect of gas bubble dynamics on the electrolysis with taking bubble-induced micro-convection into consideration. From the background mentioned above, in this study, we conducted three-dimensional coupling numerical simulation of two-phase flow and electrochemical phenomena and analyze influence of the convection with micro bubbles on the ion transportation and a cell overpotential. Moreover, we discuss the influence of the bubble atomization on the efficiency under various bubble conditions. Two-phase flow is simulated with lattice kinetic scheme (LKS) including a phase-field model proposed by Inamuro [7]. The rate of electrochemical reaction is calculated given by Butler-Volmer equation. The ion mass transportation in the electrolyte is simulated with Nernst-Planck equation. The electrical field generated by applying a voltage on the electrodes is governed by Maxwell’s equation. We use a nickel for both electrodes and 6 mol/L KOH solution for the electrolyte. The cell temperature is 298 K, and bubble size is less than 1 mm. The water electrolysis is simulated under constant current; the average of current density is 820 mA/cm2. Time variations of the cell overpotential is shown in Fig.1. The flow is generated by bubble rising and the cell overpotential is suppressed. The overpotential suppression by the flow overcomes an overpotential increase by the presence of gas bubbles preventing ion transportation in the electrolyte. Moreover, this overpotential suppression is enhanced by bubble atomization. The overpotential suppression can be separated into two types of an overpotential; one is an ohmic loss, the other is an anodic concentration overpotential. Fig.2 illustrates time variations of drop in ohmic loss and anodic concentration overpotential. Both of the overpotential constantly decreases with time. The anodic concentration is suppressed by promoting ion transportation to the anode surface and ohmic loss is suppressed by mixing the electrolyte. Fig.3 shows three-dimensional concentration distribution, and the 2 mol/L iso-surface is also illustrated in this figure. The iso-surface shifts to the anode side with increases in the number of bubbles, and smaller bubble accelerates ion transportation to the electrode and decreases the anodic overpotential and ohmic loss. This result can be explained by the result reported by Guan [8] that a smaller bubble lowers the lift force against a wall and approaches closer to the wall. [1] Pletcher, D. & Li, X. Int. J. Hydrogen Energy 36, 15089–15104 (2011). [2] Qian, K., Chen, Z. D. & Chen. J. J. J, J. Appl. Electrochem. 28, 1141–1145 (1998). [3] Janssen, L. J. J. J. Appl. Electrochem. 30, 507–509 (2000). [4] H, Vogt. Electrochim. Acta 38, 1421–1426 (1993). [5] Mat, M. D. & Aldas, K. Int. J. Hydrog. Energyn 30, 411–420 (2005). [6] Hreiz, R., Abdelouahed, L., Fünfschilling, D. & Lapicque, F. Chem. Eng. Reseach Des. 100, 268–281 (2015). [7] Inamuro, T., Yokoyama, T., Tanaka, K. & Taniguchi, M. Comput. Fluids 137, 55–69 (2016). [8] GUAN, C., YANASE, S., MATSUURA, K., KOUCHI, T. & NAGATA, Y. Japan Soc. Fluid Mech. 37, 281–289 (2018). Figure 1

Numerical Simulation of Two-Phase Flow Within Aerated-Liquid Injectors

Aerated-liquid atomization involves the injection of a small amount of gas into a liquid stream to initiate primary breakup within the injector itself. The sprays that result have good penetration and lateral dispersion characteristics, and are suitable for fueling high-speed air-breathing propulsion systems. In this study, the flow within aerated-liquid injectors featuring both inside-out and outside-in aeration schemes is simulated using an implicit large-eddy simulation method equipped with a sharp phase-interface-capturing technique and a continuum model for surface tension. Results are compared with time-averaged and time-resolved X-ray measurements of liquid-phase density and imaging obtained at the 7-BM beamline at Argonne National Laboratory using beryllium injector models. A good agreement between computational predictions and experimental measurements is generally achieved, with each indicating that the end state of the aeration process for both injector designs is the formation of a core-annular two-phase flow in the nozzle portion of the injectors. The numerical model is less successful in predicting the structure of the separated two-phase flows observed before the expansion of the mixture through the nozzle. One-dimensionalized liquid-phase density, velocity, and momentum flux distributions obtained from the numerical model and the experiment display a close agreement for all injector configurations.

Numerical Simulation of Internal Flow and External Atomization in Pressure Swirl Nozzle

A computational fluid dynamics (CFD) study is carried out on the internal flow characteristics of pressure swirl nozzle and the breakup of external liquid film outside the nozzle. The numerical simulation of two-phase flow shows the unsteady characteristics inside the nozzle and the breaking mechanism of liquid film outside the nozzle. In the nozzle, the numerical simulation reveals the three-dimensional velocity distribution in the swirl chamber and the nozzle outlet. At the same time, the study shows that the breakup of liquid film is caused by the circumferential disturbance wave produced by R-T instability under the condition of 0.7 MPa inlet pressure. The influence of inflow characteristics on the instability of liquid film is pointed out.