Fluid Multiphase Flow Model Research Articles

Evolution mechanism and interaction of the muzzle combustion-gas jets field of underwater dual-barrel synchronized launch

Despite a certain amount of research that has been done on the muzzle combustion–gas jet field of underwater launching in recent years, there are still few reports on the evolution mechanism and interaction of underwater dual-barrel synchronised launch flow fields. To fill this gap, this study aimed to numerically analyse the effects of different barrel intervals on the transient jet field evolution characteristics of the dual-barrel launch. The three-dimensional unsteady multi-phase mathematical model was created and compared with an underwater sealed emission experiment of data for verification. The volume of fluid multi-phase flow model is used to describe the gas–liquid two-phase flow process, and the k–ε turbulence model simulates the turbulent mixing phenomenon in the jet field. On this basis, the user-defined function coupling internal ballistics process was used to determine the transient jet field of a double-barrelled, 30 mm (d = 30) underwater artillery numerically at the barrel intervals of 3d, 4d and 5d. The calculation results indicate that the closer the interval is, the more chaotic the pressure field is, and the Mach disc structure forms later. When the barrel interval is 3d, the Mach disc formation time is ∼ 0.2 ms, while it forms at ∼ 0.15 ms when the barrel interval is 5d. The movement law of projectiles in water is consistent with the change of Mach disc displacement with time, and both satisfy the exponential growth law. The velocity field core is elliptical, and the vortices on both sides of the muzzle continue to grow within 0.4 ms when the launch interval is 3d. As the barrel interval increases, the core of the velocity field is bottle-shaped, the vortex on both sides of the muzzle increases first and then decreases within 0.4 ms, and the maximum temperature of the flow field increases by 15 %.

Numerical investigation of sequential water entry for two projectiles at varied entry angles

In this paper, the effect of the water entry angle on the sequential water entry process of two projectiles was investigated numerically. A numerical method is established based on the STAR-CCM+ fluid simulation software, which employs the finite volume method, the volume of fluid multiphase flow model, and overlapping grid technology. The validity of the numerical method was confirmed by comparing the simulation results with experimental data. The sequential water entry processes are simulated at angles of 90°, 75°, 60°, 45°, and 30°, respectively. The flow field characteristics, motion stability, and drag reduction of both projectiles are analyzed. The results show that projectile 1 generates a series of air bubbles shedding from its cavity's tail, which distorts projectile 2's cavity. This air bubble reduces the wet area at projectile 2's head, enhancing its drag reduction capability. Projectile 1's motion remains unaffected by projectile 2 under varying water entry angles, while distinct motion characteristics are observed in projectile 2 due to significant interference from projectile 1. These results provide valuable theoretical insights for further research on sequentially launched trans-media weapons.

Incompressible versus compressible fluid flow models: A case study on furnace tap-hole lancing

Pyrometallurgical furnaces, essential for metal extraction, operate at temperatures exceeding 1600°C and represent complex multiphase systems that challenge direct industrial research. Multiphysics models play a key role in shedding light on their intricate behaviours, supporting the refinement of design and operational strategies. Integral to the operation are the tap-holes, which facilitate the removal of molten products and are routinely opened by lancing, a process comparable to the use of a cutting torch, where high temperatures result from oxygen reacting with an iron lance. When the lance pierces the clay, oxygen gas enters the furnace, which could influence the behaviour of the molten material inside. In this work, a multiphase fluid flow model was used to investigate bulk flow dynamics, with a focus on the effects of the lancing process on the inside of the furnace, immediately behind the tap-hole. Incompressible and compressible multiphase fluid solvers were used and compared with respect their performance - the intention was to assess whether using a compressible solver would yield a different solution to the incompressible one. It was concluded that there are negligible disparities in bulk fluid flow behaviour between the solvers for the case studies examined, indicating that solver selection might be less consequential for certain aspects of oxygen lancing.

Analyzing cavity evolution and motion characteristics of asynchronous parallel oblique water-entry super-cavitating projectile

Based on the volume of fluid multiphase flow model and the overset mesh technique, a numerical method for an asynchronous parallel oblique water-entry super-cavitating projectile was established. Experimental studies of the oblique water-entry of a high-speed single-launch projectile were carried out to validate the viability of the numerical method. The paper performed the numerical simulations and analyses of cavity evolution and motion characteristics of the front and rear projectiles in different initial intervals and in two sequences of top-side water-entry projectile first and bottom-side water-entry projectile first. The results show that when the initial interval of the first launch projectile is 0.5 time the projectile length, the first launch projectile cannot produce a cavity to completely encapsulate the projectile due to the violent squeezing of the following launch projectile cavity, and its movement is seriously affected and eventually loses its trajectory stability. At the same time, the first launch projectile that enters water from top side is squeezed to a larger degree than the one from bottom side, and the wetting phenomenon occurs earlier and loses stability faster. As the initial interval increases, the influence of the following launch projectile cavity near the first launch projectile is weakened, and the first launch projectile in both water entry sequences move steadily. For the following launch projectile, due to the continuous influence of the first launch projectile cavity, its cavity is always asymmetrical, and its motion stability is affected. The following launch projectile deflects to the inner side and destabilizes when the initial interval is 0.5 times the projectile length. When the initial interval is 1 time the projectile length, it moves steadily. It deflects to the outer side and destabilizes when the initial interval is 2 and 3 times the projectile length. In addition, the motion characteristics of the following launch projectile are basically identical in two water-entry sequences.

A compressible multiphase Mass-of-Fluid model for the simulation of laser-based manufacturing processes

A new model for compressible multiphase flows involving sharp interfaces and phase change is presented, that uses a variant of the Volume-of-Fluid model to track phases by advecting their respective mass, and is hence called Mass-of-Fluid model. The framework is aimed at predicting the coupled multi-physical phenomena involved in most processes encountered in laser material processing, with the aim of minimizing a priori assumptions on the nature of the process. Emphasis is put on the multiphase fluid flow model, especially on the treatment of compressibility and phase change. The model’s accuracy and suitability is demonstrated on problems of increasing complexity, including well-known benchmarks and problems encountered in laser material processing, where simulation results are compared to experimental observations.

Cavity evolution of ventilated vehicle launch under a rolling condition

The unsteady development of the tail cavity of a vehicle after it leaves a tube often causes adverse effects, most notably an impact load on the vehicle when the cavity ruptures. The rolling of the launch platform can alter the development of the tail cavity, significantly altering the influence of the impact load on the motion and attitude of the vehicle. The present study employs the shear stress transport k-w model, the volume of fluid multiphase flow model, the Schnerr–Sauer cavity model, and the overlapping mesh technique to conduct numerical simulations of the underwater launching process of a ventilated vehicle under both stationary and rolling boundaries. A comparative analysis is conducted to examine the evolution of the cavity shape, pressure distribution, and collapse-induced load in the tail cavity under various conditions after vehicle launch. The findings suggest that the rolling of the tube induces an asymmetrical development of the shoulder cavity lengths and widths on both the windward and leeward sides, with the result of a lower peak pressure at the cavity closure position compared with that under stationary conditions. The rolling of the tube reduces the internal velocity within the tail cavity, elevates the rupture position of the tail cavity, delays the tail cavity rupture, impacts the timing of the force peak occurrence in the vertical direction of the vehicle, reduces the high pressure at the point of tail cavity rupture, and modifies the post-rupture structural characteristics of the tail cavity.

Numerical study on the influence of centroid‐to‐buoyancy center ratio on the motion stability of supercavitating vehicle

SummaryIn order to study and solve the influence of the change of the position of the centroid of the supercavitating vehicle on the motion stability, the influence law of the position of the centroid of the supercavitating vehicle on the motion stability is found, and the quantitative criterion that can guide the design of the supercavitating vehicle is summarized. On the basis of theoretical analysis, the dynamic mesh technology combined with the volume of fluid multiphase flow model and the rigid body six degrees of freedom motion calculation model is used to carry out the supercavitating vehicle motion and supercavitating flow field coupling numerical simulation research for supercavitating vehicles with different cavitator shapes. The results show that the position relationship between the centroid position and the buoyancy position has a great influence on the motion stability of the vehicle. When the center of buoyancy is before the center of mass, the vehicle is unstable; when the center of buoyancy is behind the center of mass, the vehicle sails stably, and when the position of buoyancy action coincides with the center of mass, the amplitude of the tail beat of the vehicle is the smallest, and the navigation is the most stable, which is the best position of the centroid. In this article, the concept of centroid‐to‐buoyancy center ratio is proposed. The so‐called centroid‐to‐buoyancy center ratio refers to the ratio of the length from the centroid to the top of the head of the supercavitating vehicle to the length from the center of buoyancy to the top of the head of the vehicle. When the centroid‐to‐buoyancy center ratio fluctuates in the range of [0.8–1], it is an ideal condition for the stable navigation of the vehicle. When the centroid‐to‐buoyancy center ratio is in the range of (0, 0.8), the tail beat frequency is high, which accelerates the kinetic energy consumption and the rapid instability of the vehicle. Therefore, under the same constraint conditions, it is not that the closer the center of mass is, the better the stability of the vehicle motion is. The optimal centroid position is not a certain “point,” but a “periodic fluctuation interval” that changes with the buoyancy center.

Digital twin of biomass/coal co-firing circulating fluidized bed boiler by using computational fluid dynamics simulation

Combining biomass fuel with coal in circulating fluidized bed (CFB) boilers is attractive as the increasing of energy demand. The characteristics of biomass/coal co-firing in the industrial boiler are then investigated using computational fluid dynamics (CFD). In this study, fuels of interest are coal, wood chips, and bark. The fuel proportions were set for investigating their effects on the combustion using a simplex centroid mixture design. CFD simulations consist of a standard k-epsilon viscosity flow model, Euler multiphase fluid flow model, and a simplified biomass-char combustion reaction model. The predictive responses of the model are bed temperature, heat flux, and carbon dioxide (CO2) and carbon monoxide (CO) mass flows. The simulation results showed that the operation with coal gave the highest temperature and heat flux, followed by wood chips and bark. On the other hand, the operation with biomass releases fewer gas emissions, CO2 and CO, than those of the operation with coal. The type and proportion of boiler fuel can be easily determined using two methods: predictive equation and ternary contour plot graph, which can be likened to the digital twin of biomass/coal co-firing boiler.

Numerical simulation of miscible multiphase flow and fluid–fluid interaction in deformable porous media

AbstractThe focus of the underlying research work is on the macroscopic modeling of unstable multiphase fluid flow in deformable porous media, where a lower‐viscous fluid is displaced by a more viscous fluid. This process leads to the formation of channel‐like networks, called viscous fingering. The instability effect is involved in a wide range of different fields in engineering. Some of the most common applications include carbon sequestration to store carbon dioxide (CO2) in underground reservoirs, contaminant transport in geostructures, in industrial processes, such as filtration, catalytic reactions, and in the operation of polymer electrolyte membrane fuel cells with multiphase flow in the gas diffusion layers. In this work, ideal miscible water–glycerin fluids are considered. It is assumed that the interacting fluids in the deformable porous media are incompressible. In addition, a dispersion–diffusion law is applied to capture the fluid–fluid interactions. The presence of a deformable porous material adds additional effects to the problem of the multiphase flow in porous media. The stresses in the porous solid matrix lead to changes in the porosity and influence the flow velocity of the fluids. To couple the deformable porous media with the multiphase flow, a macroscopic approach is used that relies on the theory of porous media. For the porous solid matrix, a linear elastic material model within small strains assumption is applied. The influence of the deformation‐dependent porosity on the instability is studied for 2D simulations, such as a multilayered geometry with different elastic parameters. The presented coupled nonlinear system of differential equations is simulated with the finite element method. Furthermore, a stabilization technique based on the quasi‐compressibility method is used.

Application of Smoothed Particle Hydrodynamics for Modeling of Multiphase Fluid Flow in Non-Uniform Porous Media

Application of Smoothed Particle Hydrodynamics for Modeling of Multiphase Fluid Flow in Non-Uniform Porous Media

Research on cavity collapse characteristics during high-speed water-exit of the supercavitating projectile

During high-speed water-exit of the supercavitating projectile, the cavity interacts with the free surface and collapses, with instantaneous high collapse pressure impacting on the projectile. In order to study the cavity collapse characteristics during high-speed water-exit of the supercavitating projectile, the numerical study based on the Reynolds-averaged equation and the volume of fluid multiphase flow model is conducted in this paper. The results show that the cavity near the free surface will gradually become larger with the movement of the projectile during water-exit of the supercavitating projectile. The existence of attitude angles will cause the asymmetry of cavity to collapse. The cavity on the upstream side will first collapse and generate collapse pressure, while the cavity on the downstream side will collapse later but generate higher collapse pressure. The asymmetry of the cavity collapse becomes stronger with the increasing attitude angles. The time interval of the collapse pressure on the downstream and upstream sides of the projectile becomes shorter close to the projectile tail.

Experimental Time-Lapse Visualization of Mud-Filtrate Invasion and Mudcake Deposition Using X-Ray Radiography

Accurate description and modeling of multiphase fluid flow are of paramount importance for subsurface resource engineering. The main source of information to quantify in-situ rock properties are borehole geophysical measurements, which are very often riddled with uncertainty ensuing from rock heterogeneity/anisotropy and mud-filtrate invasion effects. Therefore, experimental methods are needed to accurately describe and quantify the physics of mud-filtrate invasion and mudcake deposition and its effects on borehole geophysical measurements. We developed a new high-resolution (10 to 50 μm) experimental method to investigate the invasion of water- and oil-based drilling muds into rectangular rock samples using X-ray radiography. During mud injection, rock simples are scanned using high-resolution X-ray radiography, enabling the time-lapse visualization of both mud-filtrate invasion and external/internal mudcake deposition. Our experimental method successfully examines the effects of rock heterogeneity, bedding plane orientation, and anisotropy on the spatial distribution of fluids and mudcake formation resulting from mud-filtrate invasion. It also emphasizes the importance of mud properties on the final fluid saturation state once mudcake seals the borehole. The procedure is fast, accurate, and reliable to quantify the process of mud-filtrate invasion at the core scale, enabling an improved understanding of invasion effects on borehole geophysical measurements following drilling operations, especially in spatially complex rocks such as laminated sandstones and carbonates.

Effect of produced carbon dioxide on multiphase fluid flow modeling of carbonate acidizing

A two-scale continuum (TSC) numerical model is used at pore and Darcy scales to model and optimize the matrix acidizing dissolution process. During matrix acidizing process in carbonate reservoir, the solubility of carbon dioxide, as one of the hydrochloric acid/calcite reaction products, is limited, which leads to the formation of a separate gas phase in the reservoir based on pressure and temperature. The presence of this free gas has nonlinear effect on the fluid flow and phase distribution in porous media due to the alteration in the relative permeability of the injected/spent acid. Density and viscosity of the spent acid will also be changed. Ignoring these effects on TSC model can reduce the accuracy of the final results compared to similar laboratory studies. The significance of our study is to examine and apply the nonlinear effects of produced carbon dioxide on wormhole propagation, dissolution patterns, and breakthrough curves at different injection rates of the acid. The innovation presented in this study is the evaluation of the effect of the presence of the gaseous carbon dioxide produced during the hydrochloric acid and calcite reaction on the relative permeability of the injected acid. This effect has been numerically investigated and solved along with the governing equations of the matrix acidizing at different time steps. In our work, The TSC model is coupled with a nonlinear relative permeability model to consider the effect of free carbon dioxide. Density, viscosity, and solubility correlations are also coupled with TSC model to update fluid properties during acid propagation and acid/rock interactions. The final results show that the neglecting of free gas affects the accuracy of wormhole propagation estimation. The model shows better agreement with the experimental data to predict the rock dissolution patterns and wormhole breakthrough. By considering free gas, the model can track thicker wormholes due to the free gas blockage and the slower acid/rock reaction rate. Our approach showed that isothermal models are not accurate enough to predict the change in carbon dioxide solubility at higher temperatures. Reduction in solubility affects the acid's relative permeability and increases the volume of acid required for the breakthrough. Hence, the developed model improves our knowledge of wormhole propagation during carbonate acidizing.

Research on drag reduction characteristics of the surface of springtail cuticle

The technology of underwater drag reduction is one of critical paths to break through the problem of ocean-going, and the bionic drag reduction is a very promising method. The bionic drag reduction uses sliding effect on the liquid-gas interface to reduce the drag, while the gas film is very unstable and the drag reduction function is easy to fail. The concave corner microstructure of springtail cuticle can make the air retention, which has very important significance to solve the problem of instability of gas film. In the paper, a model is established by referring to the concave corner microstructures of springtail cuticle. The k-ε turbulence model and volume of fluid multiphase flow model were used. The results show: the simulation model can be used to calculate the flow characteristics of the concave corner microstructure of springtail cuticle; as the area ratio of free shear increases, so does the drag reduction rate, which is beneficial for drag reduction; the drag reduction rate of different microstructure is slightly different, but it is mainly related to the area ratio of free shear of microstructure.

A multiscale LBM–TPM–PFM approach for modeling of multiphase fluid flow in fractured porous media

AbstractIn this paper, we present a reliable micro‐to‐macroscale framework to model multiphase fluid flow through fractured porous media. This is based on utilizing the capabilities of the lattice Boltzmann method (LBM) within the phase‐field modeling (PFM) of fractures in multiphase porous media. In this, we propose new physically motivated phase‐field‐dependent relationships for the residual saturation, the intrinsic as well as relative permeabilities. In addition, an anisotropic, phase‐field‐dependent intrinsic permeability tensor for the fractured porous domains is formulated, which relies on the single‐ and multiphasic LBM flow simulations. Based on these results, new relationships for the variation of the macroscopic theory of porous media (TPM)–PFM model parameters in the transition zone are proposed. Whereby, a multiscale concept for the coupling between the multiphasic flow through the crack on one hand and the porous ambient, on the other hand, is achieved. The hybrid model is numerically applied on a real microgeometry of fractured porous media, extracted via X‐ray microcomputed tomography data of fractured Berea Sandstone. Moreover, the model is utilized for the calculation of the fluid leak‐off from the crack to the intact zones. Additionally, the effects of the depth of the transition zone and the orientation of the crack channels on the amount of leakage flow rates are studied. The outcomes of the numerical model proved the reliability of the multiscale model to simulate multiphasic fluid flow through fractured porous media.

Numerical study of elbow erosion due to sand particles under annular flow considering liquid entrainment

Sand particle erosion is always a challenge in natural gas production. In particular, the erosion in gas–liquid–solid annular flow is more complicated. In this study, a three-phase flow numerical model that couples the volume of fluid multiphase flow model and the discrete phase model was developed for prediction of erosion in annular flow. The ability of the numerical model to simulate the gas–liquid annular flow is validated through comparison with the experimental data. On the basis of the above numerical model, the phase distribution in the pipe was analyzed. The liquid entrainment behavior was reasonably simulated through the numerical model, which guaranteed the accuracy of predicting the particle erosion. Additionally, four erosion prediction models were used for the erosion calculation, among them, the Zhang et al. erosion model predicted the realistic results. Through the analysis of the particle trajectory and the particle impact behavior on the elbow, the cushion effect of the liquid film on the particles and the erosion morphology generation at the elbow were revealed.

Study of CO2 injection in a depleted oil reservoir using geomechanically coupled and non-coupled simulation models

This study seeks to understand CO2 injection into a depleted reservoir through multiphase fluid flow and geomechanical modeling simulations using field data. A comparison of the one-way geomechanically coupled and non-coupled models is presented. Results suggest that computed fluid pressure response and CO2 distribution in the reservoir are significantly influenced by reservoir geomechanical properties. The non-coupled model shows <50% of CO2 penetration distance and laterally shallower reservoir pressure changes compared to the coupled model after 53 days of injection. However, in the non-coupled model, CO2 concentration is significantly higher at short distances from the injection well compared to the coupled model. This reservoir behavior was attributed to the alteration in relative permeabilities caused by changes in geomechanical properties in the coupled model. Therefore, upon the availability of computing resources, one should use more computationally intensive but accurate models involving two-way-coupling. Finally, accurate determination of engineering properties and proper geological characterization is desirable for meaningful prediction models.

Virtual flow metering of production flow rates of individual wells in oil and gas platforms through data reconciliation

In the present work, virtual flow metering (VFM) tools are developed to provide estimates for the individual flow rate measurements of the wells operated simultaneously in typical oil and gas platforms. Data reconciliation (DR) procedures are used to calibrate phenomenological models using available measured profiles of well pressure and temperature, and overall flow rates of gas, oil and water. In order to evaluate the relative importance of key hypotheses, three different phenomenological models were used to describe the platform operation: (i) a simple single phase fluid flow model, to evaluate whether the DR task can be successfully accomplished with the available data; (ii) a simple multiphase fluid flow model, in order to evaluate whether the explicit consideration of the multiphase nature of the problem can affect the obtained DR results; and (iii) a detailed phenomenological multiphase flow model, to represent accurately the behavior of an oil and gas production platform. Obtained results show that the proposed DR scheme can be indeed implemented successfully in the form of a VFM sensor to assign online and in real time the individual production of wells operated simultaneously in typical oil and gas platforms. The DR-based VFM was able to reconcile total oil and total water flow rates with average relative deviations of 0.87% and 17% respectively and maximum deviation of 2.3% for oil flow rates. Besides, the DR-based VFM tool provided insights about the system behavior and sensoring management, being able to indicate the oil lines and sensors that were subject to the highest variability.

CFD-based calculation method of convective heat transfer coefficient of spiral bevel gear in intermediate gearbox under splash lubrication

Purpose This paper aims to propose a numerical method to calculate the convective heat transfer coefficient of spiral bevel gears under the condition of splash lubrication and to reveal the lubrication and temperature characteristics between the gears and the oil-air two-phase flow. Design/methodology/approach Based on computational fluid dynamics, the multiple reference frames (MRF) method was used to simulate the rotational characteristics of gears and the motions of their surrounding fluid. The lubrication and temperature characteristics of gears were studied by combining the MRF method with the volume of the fluid multiphase flow model. Findings The convective heat transfer coefficient can be improved by increasing the rotational speed and the oil immersion depth. Moreover, the temperature of the tooth surface having a large convective heat transfer coefficient is also found to be low. A large convection heat transfer coefficient could lead to a good cooling effect. Originality/value This method can be used to obtain the convective heat transfer coefficient values at different meshing positions, different radii and different tooth surface positions. It also can provide research methods for improving the cooling effect of gears under the condition of splash lubrication. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2020-0233/

Boron Removal from Metallurgical-Grade Silicon by Slag Refining and Gas Blowing Techniques: Experiments and Simulations

To enhance the removal of B from metallurgical-grade Si (MG-Si) by the CaO-SiO2-CaCl2 slag refining technique, Ar gas was injected during the refining process. The effects of the refining time, Ar gas flow rate, and the blowing-pipe immersion depth on the removal of B from MG-Si were studied. The results show that the injection of Ar gas can effectively stir and then mix the Si and slag phases, resulting in an increase in the Si/slag contact area and in an acceleration of the mass transfer rate of B. With the combined slag-refining and Ar gas-blowing approach, the reaction time for the removal of B was reduced to 5 min from 75 min required with the slag-refining approach. Correspondingly, the content of B was reduced from 23.91 to 10.42 ppmw, with a removal efficiency of 56.42%. The results were confirmed by the coupled large-eddy simulation model and the volume of fluid multiphase flow model.