Showing papers on "Multiphase flow published in 2023"

Multiphase coupling transport evolution mechanism of the free sink vortex

Abstract: The sink vortex with a free surface exists some physical processes in the suction evolution process, such as multiphase coupling, mass transfer, and intensive energy exchange. Here, the transport mechanism of multiphase coupling is a complex dynamics problem with highly nonlinear characteristics. The mechanical modeling and numerical solution of multiphase viscous coupled transport face a significant challenge. To address the above problem, a multiphase coupling transport modeling-solving method of the free sink vortex is proposed. Based on the coupled level set and volume-of-fluid (CLSVOF) method, a multiphase coupling transport model of the free sink vortex is set up with a continuous surface tension model and a realizable (k-ε) turbulence model. An effective volumetric correction scheme calculates the high-speed rotating flow and ensures the mass conservation of flow fields and the velocity field without divergence. Then, an interphase coupling solution approach accurately traces the multiphase fluid distribution and multiphase interface. The multiphase coupling interface and cross-scale vortex cluster transport laws are obtained according to the multi-characteristic physical variables. The interaction mechanism between the multiphase coupling transport process and the pressure pulsation characteristics is revealed. The results show that the multiphase coupling transport is the critical state of the fluid medium transition. The vortex microclusters are subjected to different spatiotemporal disturbance modes and form the layered threaded waveforms at the interface. With the increment of the nozzle sizes, the multiphase coupling process enhances, and the coupling energy shock causes nonlinear pressure pulsation. It can offer valuable references to the research works of the vortex transport mechanism, cross-scale solution of vortex cluster, and flow pattern tracking.

Fluid-Solid Coupling-Based Vibration Generation Mechanism of the Multiphase Vortex

Abstract: Multiphase vortices are widely present in the metallurgical pouring processes, chemical material extraction, hydroelectric power plant energy conversion, and other engineering fields. Its critical state detection is of great significance in improving product yield and resource utilization. However, the multiphase vortex is a complex dynamics problem with highly nonlinear features, and its fluid-induced vibration-generation mechanism faces significant challenges. A fluid-solid coupling-based modeling method is proposed to explore mass transfer process with the vorticity distribution and vibration-generation mechanism. A vibration-processing method is utilized to discuss the four flow-state transition features. A fluid-induced vibration experiment platform is established to verify the numerical results. It is found that the proposed modeling method can better reveal the vibration-evolution regularities of the fluid-solid coupling process. The flow field has a maximum value in the complex water–oil–gas coupled flow process, and induces a pressure pulsation phenomenon, and its frequency amplitude is much larger than that of the water phase and water–oil two-phase flow states. In the critical generation state, the increasing amplitude and nonlinear step structure of high-frequency bands (45 Hz~50 Hz) and random pulse components can be used for the online detection of multiphase-coupling states.

Intelligent Measurement of Void Fractions in Homogeneous Regime of Two Phase Flows Independent of the Liquid Phase Density Changes

Abstract: Determining the amount of void fraction of multiphase flows in pipelines of the oil, chemical and petrochemical industries is one of the most important challenges. Performance of capacitance based two phase flow meters highly depends on the fluid properties. Fluctuation of the liquid phase properties such as density, due to temperature and pressure changes, would cause massive errors in determination of the void fraction. A common approach to fix this problem is periodic recalibration of the system, which is a tedious task. The aim of this study is proposing a method based on artificial intelligence (AI), which offers the advantage of intelligent measuring of the void fraction regardless of the liquid phase changes without the need for recalibration. To train AI, a data set for different liquid phases is required. Although it is possible to obtain the required data from experiments, it is time-consuming and also incorporates its own specific safety laboratory consideration, particularly working with flammable liquids such as gasoline, oil and gasoil. So, COMSOL Multiphysics software was used to model a homogenous regime of two-phase flow with five different liquid phases and void fractions. To validate the simulation geometry, initially an experimental setup including a concave sensor to measure the capacitance by LCR meter for the case that water used as the liquid phase, was established. After validation of the simulated geometry for concave sensor, a ring sensor was also simulated to investigate the best sensor type. It was found that the concave type has a better sensitivity. Therefore, the concave type was used to measure the capacitance for different liquid phases and void fractions inside the pipe. Finally, simulated data were used to train a Multi-Layer Perceptron (MLP) neural network model in MATLAB software. The trained MLP model was able to predict the void fraction independent of the liquid phase density changes with a Mean Absolute Error (MAE) of 1.74.

Using ANN and Combined Capacitive Sensors to Predict the Void Fraction for a Two-Phase Homogeneous Fluid Independent of the Liquid Phase Type

Abstract: Measuring the void fraction of different multiphase flows in various fields such as gas, oil, chemical, and petrochemical industries is very important. Various methods exist for this purpose. Among these methods, the capacitive sensor has been widely used. The thing that affects the performance of capacitance sensors is fluid properties. For instance, density, pressure, and temperature can cause vast errors in the measurement of the void fraction. A routine calibration, which is very grueling, is one approach to tackling this issue. In the present investigation, an artificial neural network (ANN) was modeled to measure the gas percentage of a two-phase flow regardless of the liquid phase type and changes, without having to recalibrate. For this goal, a new combined capacitance-based sensor was designed. This combined sensor was simulated with COMSOL Multiphysics software. Five different liquids were simulated: oil, gasoil, gasoline, crude oil, and water. To estimate the gas percentage of a homogeneous two-phase fluid with a distinct type of liquid, data obtained from COMSOL Multiphysics were used as input to train a multilayer perceptron network (MLP). The proposed neural network was modeled in MATLAB software. Using the new and accurate metering system, the proposed MLP model could predict the void fraction with a mean absolute error (MAE) of 4.919.

Multiphase flow development in gravitational and magnetic fields

Abstract: Multiphase flows of non-Newtonian fluid with heat transfer through an inclined channel are presented in this article. Eyring-Powell fluid is considered the main continuous phase. Two separate types of bi-phase suspensions are formulated with the help of gold and silver metallic particles under the effects of applied magnetic fields. Mathematical expressions for multiphase flow dynamics are developed employing Eyring-Powell fluid's stress tensor. Thermal transport is governed by Fourier's law of conduction. A semi-analytic solution is obtained for the nonlinear and coupled differential equations. The present results are compared with the Newtonian multiphase flows for the limiting case. The study reveals that gold particles offer less drag as compared to silver particles in the multiphase suspensions. Moreover, Eyring-Powell fluid is more suitable for viscous suspensions.

Research on energy conversion characteristics in impeller of Helico-Axial Multiphase Pump during crude transportation

Abstract: In order to explore the influence of different crude viscosity on the energy conversion characteristics of impeller of Helical-Axial Multiphase Pump, it was carried out numerical simulation which based on the standard k-ε equation and Euler multiphase flow model under different viscosity. At the same time, Helical-Axial Multiphase Pump was analyzed internal flow structure of by experiments when transported water. The changes of pressure, GVF（gas volume fraction）, flow field and pressurization are obtained in impeller with different viscosity and IGVF（inlet gas volume fraction）.The results show that liquid viscosity is greater, the inlet pressure of impeller increasing, velocity vector is greater near rim and hub side, increasing of turbulent kinetic energy of the hub side and rim side, resulting in greater flow loss. The pressurization capacity of impeller is weakened, making its head is lower. At the same time, the fluctuation of GVF from inlet to outlet is smaller, and the low GVF area is mainly concentrated in high pressure area. The viscosity has a greater impact on static pressure energy of the first half of impeller, and a smaller impact on the second half of impeller, and the power of impeller is mainly concentrated in the first half of impeller.

Study on the blade squealer tip affecting tip leakage flow and performance of a multiphase pump

Abstract: To improve the adverse effects of tip leakage flow on the multiphase pump, a method to design a squealer tip on the impeller blade was proposed in this paper. The effect of the squealer tip on external characteristic, tip clearance flow characteristic and energy dissipation of the multiphase pump are analyzed. Research results indicate that the blade squealer tip can effectively improve hydraulic efficiency of the multiphase pump. At the optimal efficiency point, the head and hydraulic efficiency of the multiphase pump with squealer tip increased by 3.62% and 4.15% respectively compared with the original model. The influence of tip leakage flow in the axial rear half passage of the multiphase pump impeller is far greater than that in the axial forward half passage, especially on the back position in the middle of the impeller passage. The squealer tip can restrain the reverse of leakage flow from the pressure side to the suction side of the impeller blade and the clearance leakage flow of the model with squealer tip is smaller than that of the original model. The squealer tip on blade will reduce the energy dissipation caused by unsteady flow in the mainstream. The research results in this paper can provide theoretical support for effectively restraining the influence of the tip leakage vortex on the mainstream of the helicon-axial multiphase pump, and contribute to engineering practice value of improving the performance of the multiphase pump.

Simulation of Multi-Phase Flow in Autoclaves Using a Coupled CFD-DPM Approach

Abstract: In this work, a numerical simulation study on the mixing characteristics of multiphase flow in an autoclave was carried out using CFD technology. The Eulerian–Eulerian model and discrete phase model (DPM) were employed to investigate the solid holdup, critical suspension speed, nonuniformity of solid suspension, gas holdup distribution, bubble tracks, and residence time during stirring leaching in the autoclave. Experiments validate the accuracy of the numerical model, and the experimental values correspond well with the simulation results. The numerical simulation results show that the solid–liquid mixing is mainly affected by the axial flow, the best agitation speed is 400 rpm, and increasing the speed further cannot make the mixture more homogenous and buildup occurred above the autoclave. The calculated critical suspension speed is 406 rpm, which is slightly lower than that obtained from the empirical formula. The gas phase is mainly concentrated in the vortex area above the blade. When the gas phase is in a completely dispersed state (N = 300 rpm), the average residence time of the bubbles is 5.66 s.

A pressure approach of Cumulant phase field lattice Boltzmann method for simulating multiphase flows

Abstract: The cumulant lattice Boltzmann method (LBM) has been recently used to simulate multiphase-multicomponent flows by applying an external force. Furthermore, the mass and momentum are not conserved when an external force is used. In the classical approach, the third-order derivatives in density necessitate information from a large stencil of neighbors, which affects parallelization and is computationally expensive. In this paper, we propose an equilibrium distribution function in the moment space which includes diagonal and off-diagonal elements of the pressure tensor. Consequently, the interfacial tension effect can be exerted into this equilibrium function, circumventing the need for an external force. This function is applied on the moment, central, and cumulant LBM and transferred back to the discrete space to be used in Bhatnagar-Gross-Krook (BGK) LBM. This approach's simplicity, easy-to-implement, and high parallelization capability due to removing high order derivatives are some key advantages.An immiscible two-components flow between two parallel plates is simulated and compared with the analytical solution at different viscosities for the moment LBM and the cumulant LBM. Numerical results are in good agreement with analytical solutions. Moreover, a dispersed droplet in a continuous phase under shear flow is simulated to show the capability of the proposed method in the braking-up process modeling. The method has been extended for three dimensions, and two cases of full three dimensional breakup of a liquid thread and collision of two equal droplets are studied to show the ability of this method to simulate coalescence and breakup process.

A phenomenological analysis of droplet shock-induced cavitation using a multiphase modeling approach

Abstract: Investigations of shock-induced cavitation within a droplet are highly challenged by the multiphase nature of the mechanisms involved. Within the context of heterogeneous nucleation, we introduce a thermodynamically well-posed multiphase numerical model accounting for phase compression and expansion, which relies on a finite pressure-relaxation rate formulation. We simulate (i) the spherical collapse of a bubble in a free field, (ii) the interaction of a cylindrical water droplet with a planar shock wave, and (iii) the high-speed impact of a gelatin droplet onto a solid surface. The determination of the finite pressure-relaxation rate is done by comparing the numerical results with the Keller–Miksis model, and the corresponding experiments of Sembian et al. and Field et al., respectively. For the latter two, the pressure-relaxation rate is found to be [Formula: see text] and [Formula: see text], respectively. Upon the validation of the determined pressure-relaxation rate, we run parametric simulations to elucidate the critical Mach number from which cavitation is likely to occur. Complementing simulations with a geometrical acoustic model, we provide a phenomenological description of the shock-induced cavitation within a droplet, as well as a discussion on the bubble-cloud growth effect on the droplet flow field. The usual prediction of the bubble cloud center, given in the literature, is eventually modified to account for the expansion wave magnitude.

Research on transient composition tracking in natural gas condensate pipeline networks

Abstract: Offshore pipelines are hailed as the “lifeline” of an offshore oil and gas production system and are essential for offshore oil and gas development. Component tracing technologies for the oil and gas multiphase transmission pipeline networks need to be urgently developed to predict the fluid composition changes in pipeline networks. Instead of assuming the fluid components are constant, we consider they varied with flow. The component conservation equations and a phase change model are established. The equation of state of the fluid is adopted to determine the equilibrium state of each component in real time. Considering the macroscopic flow calculation, microscopic fluid components, and phase equilibrium, the component tracking algorithm is established for natural gas condensate pipeline networks, which can dynamically track the fluid composition in pipeline networks and calculate the phase exchange amount and related flow parameters in real time. Three case studies are performed to verify the effectiveness of the algorithm. These findings are of great practical significance for understanding the gas–liquid two-phase flow in pipeline networks, promoting further engineering applications of component tracking on pipeline networks.

Review of bubble dynamics on charged liquid-gas flow

Abstract: When a fluid is subject to an electric field, it usually processes unique features compared to conventional fluid that arises from coupling between charged particles and fluid interface. Based on this commonality, we define the concept of "charged multiphase flow" and constructed a generalized charged multiphase flow system using the "Tai Chi Diagram" to analyze the properties and features of different study objects, with an emphasis on the bubble dynamics on charged liquid-gas flow object, covering the processes of bubble generation, motion and interaction, as well as the important dynamic behaviors, involved such as bubble deformation, coalescence and breakup. Furthermore, in light of the special plasma-liquid interface phenomenon formed by the ionization of gas/vapor phase in the liquid phase in strong electric fields, the traditional gas-liquid-solid three-phase flow system is expanded into a broader range of multiphase flow systems involving plasma, which enriches the theoretical and frontier scientific problems of multiphase flow. In addition, technical innovations, remaining work and future trends in the development of charged liquid-gas flow and their potential applications are discussed.

Semi-analytical solution of nonlinear hydromagnetic multiphase flow of highly viscous fluid

Abstract: Two separate types of multiphase flow models have been developed theoretically in this paper. Fourth-grade fluid model of non-Newtonian in nature is considered the main carrier. Silver and gold metallic particles of spherical shape suspend to form highly viscous multiphase flows which drift through an inclined channel. Effects of magnetic fields acting across the channel are applied as the body force. An approximate solution for the nonlinear flow dynamics of the two-phase suspensions. A comprehensive parametric study is performed to graphs against the pertinent parameters. Further, the obtained mathematical results and visual evidence are validated through computational data and found to be in completer agreement. It is inferred that gold multiphase suspensions can effectively be used in chemical and coating processes.

Impact of wettability on immiscible displacement in water saturated thin porous media

Abstract: The characterization of immiscible displacement processes at the pore scale is crucial in order to understand macroscopic behaviors of fluids for efficient use of multiphase transport in various applications. In this study, the impact of porous material wetting properties on gas invasion behavior at various gas injection rates was investigated for thin hydrophilic porous media. An experimentally validated two-phase computational fluid dynamics model was employed to simulate the dynamic fluid–fluid displacement process of oxygen gas injection into liquid water saturated thin porous media. A phase diagram was developed through a parametric characterization of the thin porous media in terms of the material hydrophobicity and gas flow rates. In addition to calculating the saturation of the invading gas, gas pressure variations were calculated and used to identify the locations of phase diagram boundaries. Non-wetting phase streamlines resolved at the microscale were visualized and presented as a novel indicator for identifying displacement regimes and phase diagram boundaries. It was observed that the crossover from the capillary fingering regime to the stable displacement regime occurred between contact angles of 60° and 80°. By increasing the gas injection rate, due to viscous instabilities, flow patterns transitioned from the capillary fingering and stable displacement regimes to viscous fingering regime.

Multiphase Flowrate Measurement With Multimodal Sensors and Temporal Convolutional Network

Abstract: Accurate multiphase flow measurement is vital in monitoring and optimizing various production processes. Deep learning has as of late arose as a promising approach for assessing multiphase flowrate dependent on various customary flow meters. In this paper, we propose a multi-modal sensor and Temporal Convolution Network (TCN) based method to predict the volumetric flowrate of oil/gas two-phase flows. The volumetric flowrates of the liquid and gas phase vary from 0.96 - 6.13 $\text{m}^{{3}}$ /h and 5.5 - 121.2 $\text{m}^{{3}}$ /h, respectively. The multi-modal sequential sensing data are simultaneously collected from a Venturi tube and a dual-plane Electrical Capacitance Tomography (ECT) sensor in a pilot-scale multiphase phase flow facility. The reference data are derived from the single-phase flowmeters. Z-score and First-Difference (FD) data pre-processing methods are employed to manipulate the collected instantaneous time series multi-modal sensing data. The pre-processed data are utilized for training the TCN model. Experimental results reveal that the TCN model can effectively predict the multiphase flowrate based on the multi-modal sensing data. The results provide guidance on data pre-processing methods for multiphase flowrate estimation and demonstrate the effectiveness of combining multi-modal sensors and TCN for multiphase flowrate prediction under complex flow conditions.

Numerical Modeling of the Cavitation Flow in Throttle Geometry

Abstract: The modern fuel injectors work with ultra-high injection pressure with a micro-size nozzle, which inevitably triggers the cavitation flow inside the nozzle. The formation of vapor bubbles and their development inside the nozzle is difficult to characterize due to its highly fluctuating spatial and temporal parameters. The numerical models can predict the temporal behavior of cavitating flow with the real-size nozzle geometry, which is fairly expensive with the experiments. A systematic study has been carried out using throttle geometry to characterize the cavitation flow. The different turbulence, multiphase, and cavitation models are extensively evaluated and validated with experimental data. A combination of numerical models has been proposed to predict the cavitation flow more accurately with low computational time. The results obtained with the k-ω SST (Shear Stress Transport) turbulence model and the ZGB (Zwart-Gerber-Belamri) cavitation model are more consistent with the experimental results. The overall structure of cavitation is well captured with both the VOF (Volume of Fluid) and the Mixture multiphase models. Although, the smaller structures like bubble formation and ligament breakup are only captured with the VOF (Volume of Fluid) tuned with the sharp interface method. The effect of pressure difference on the cavitation flow has been estimated with diesel and bio-diesel fuel. The effect of nozzle conicity on cavitation phenomena has also been reported.

Three-Dimensional High-Precision Numerical Simulations of Free-Product DNAPL Extraction in Potential Emergency Scenarios: A Test Study in a PCE-Contaminated Alluvial Aquifer (Parma, Northern Italy)

Abstract: Chlorinated organic compounds are widespread aquifer contaminants. They are known to be dense non-aqueous phase liquids (DNAPLs). Therefore, they are denser than water and immiscible with other fluids. Their migration into the environment in variably saturated zones can cause severe damage. For this reason, optimizing those actions that minimize the negative impact of these compounds in the subsurface is essential. This paper presented a numerical model simulating the free-product DNAPL migration and extraction through a purpose-designed pumping well in a potential emergency scenario. The numerical simulations were performed using CactusHydro, a numerical code that uses a high-resolution shock-capturing flux conservative method to resolve the non-linear coupled partial differential equations of a three-phase immiscible fluid flow recently proposed in the literature, including the contaminant extraction at the base of the aquifer. We investigated the temporal (and spatial) evolution of its migration in the Parma (Northern Italy) porous alluvial aquifer following the saturation contour profiles of the three-phase fluid flow in variably saturated zones. The results indicated that this numerical approach can simulate the contaminant migration in the subsurface and the pumping of the free-product from a well screened at the base of the aquifer system. Moreover, the simulation showed the possibility of recovering about two-thirds of the free-product, in agreement with the scientific literature.

Numerical investigation of the influence of surface wettability on water entry of spheres

Abstract: The water-entry problem is a complex multiphase hydrodynamic problem that is directly related to many engineering applications and natural phenomena, such as torpedo airdrops, seaplane landings, and ship slamming. Therefore, studying the influence of the microscopic properties of the object surface on the macroscopic phenomenon during water entry is necessary. In this study, the volume of fluid model and continuum surface force models are coupled to establish a multiphase flow numerical method for the water entry of objects considering surface wettability. The effect of surface wettability on the evolution of the cavity, multiphase flow-field structure, and hydrodynamic force characteristics are analyzed in detail. The results show that the movement of liquid film formed on the surface of the sphere at the early stage is the key to the formation of the cavity. For hydrophobic spheres, the liquid film separates near the equator of the sphere, and air enters it to form a cavity. At the moment of pinch-off, the pressure in the lower cavity increases, which generates a force that pushes the sphere to accelerate the fall, and this force is higher for spheres with a smaller density ratio. The flow-field structure shows that both rotational and shear effects play a dominant role in the evolution of the flow field in the cavity. For hydrophilic spheres, the liquid film follows the contact line along the surface of the sphere and converges at the top to form an upward jet.

3D Modelling of double elbow pipeline erosion in methane – water – sand multiphase medium

Abstract: Introduction. In gas industry, predicting sand erosion damage of pipelines by sand particles is a difficult task because this process is strongly influenced by many factors. Particulate matter carried away by the multiphase product during production can seriously compromise the integrity of fluid handling structures such as pipelines and elbows. Materials and methods. A three-dimensional numerical modelling approach in three-phase gas – liquid – solid flows was used to analyze erosion processes in pipe elbows. A key advantage of using CFD is that it can provide a wealth of information such as the effect of various parameters on erosion, maximum erosion rate, and erosion-prone areas. A variation of the Euler method for multiphase fluids was used to simulate three-dimensional unsteady gas-water annular flows with the presence of sand particles. Results. The results showed that a vertical pipe with two elbows is more prone to erosion at the second elbow than atthe first elbow. However, in a horizontal pipe with two elbows, it can be concluded that the first elbow is more proneto erosion. On the other hand, erosion at L/D = 0 showed the maximum erosion rate among all the geometries studied. Conclusions. In a vertical pipe, the second elbow of the pipeline is more susceptible to erosion. In addition, the erosion rate at the second elbow of vertical and horizontal pipes is the same for all studied geometries. The pipeline with L/D = 10 showed the optimal layout choice for vertical and horizontal pipe with an average erosion rate of 57.9 mm/year, which representsthe lowest erosion rate among the options studied.

Numerical investigation of gas–liquid two-phase performance in a mixed-flow pump by using a modified drag force model

Abstract: As key devices to lift deep-sea oil and gas, mixed-flow pumps can transport multiphase flow with high inlet gas volume fraction (IGVF). Performance parameters of mixed-flow pumps may be disturbed by the complex flow and gas–liquid distribution under various conditions that need an accurate two-phase flow numerical methodology for prediction. In this work, the gas–liquid mixed flow performance of a mixed-flow pump is investigated based on the modified drag force model, which considers the bubble deformation at high IGVF. The effects of the IGVF on pressure increment and gas phase distribution are explored. The influences of flow rate and rotational speed are studied as well. Experiments are conducted to obtain performance parameters and gas–liquid distribution images. The results show that performance parameters and gas–liquid distribution predicted in simulations are consistent with those obtained in experiments. The pressure increment of the mixed-flow pump is decreased as the IGVF and flow rate increase. Especially when IGVF increases from 5% to 15%, the pressure increment drops sharply, which is the surging phenomenon. The increased speed may improve the performance. The evolution of gas phase distribution is deeply analyzed to improve the understanding of gas–liquid flow characteristics in mixed-flow pumps.