Multiphase Flow Characteristics Research Articles

Investigation of the effects of pipe diameter of internal multiphase flow on pipe elbow vibration and resonance

Computational fluid dynamics modelling of internal two-phase flow induced transient forces at 90° elbows have been carried out to evaluate the effect of pipe diameter on the characteristics of multiphase flow induced vibration. Simulations of two-phase flows of slug, cap bubbly and churn induced vibration at a pipe elbow were carried out using the volume of fluid model for the two-phase flows and the k – ε model for turbulence. Modal analysis has been carried out to evaluate the risk of resonance. Results were compared across three geometrically similar pipes of different diameters. Simulation results showed that the behaviours of the flow induced forces at the pipe elbow as a function of gas velocity for internal diameters of 0.0525 and 0.2032 m are similar. However, the multiphase flow induced force characteristics are different in the 0.1016 m diameter (intermediate) pipe. It can be attributed to the transition behaviour of gas–liquid two-phase flows caused by Taylor instability in an intermediate sized pipe. The predicted root-mean-square flow induced forces as a function of Weber number were correlated with an existing empirical correlation for a wider range of pipe sizes and gas volume fractions between 40% and 80%. Furthermore, the pipe natural frequencies increase with the increase of gas volume fraction in smaller pipes and the resonance risk increases with the increase of pipe diameter.

Calculation model for drag coefficient and multi-phase flow characteristics in dust removal process: Comparison between flake aluminum powder and spherical aluminum powder

It is of great significance to study the force model of flake and spherical particles in a two-phase flow system for reducing dust hazards. In present work, the correspondence between drag coefficient Cd and Re for spherical particle is specified by a new CFD method. Moreover, 144 kinds distribution states for flake particle with equal probability are summarized into 7 kinds stress state models with different occurrence probabilities, and the corresponding relationship between the equivalent drag coefficient Cd and the equivalent Reynolds number Re is further obtained. A series of ventilation and dust removal experiments and full-scale numerical simulation in a large space are carried out, and the maximum error of peak dust concentration between the simulation results and the experimental results for flake powder is 17.4%. In addition, the size effect of flake powder is more obvious than that of spherical powder, and the fluidity of flake powder with equal particle size is obviously better than that of spherical powder, so flake powder can be removed from the production workshop faster. However, in the process of ventilation and dust removal, the diffusion risk of spherical dust larger than 100 μm do not change much during the ventilation process.

Visualization experimental and numerical study on multiphase flow characteristics of main cryogenic heat exchanger in offshore liquefied natural gas industry chain

The deep-sea natural gas resources are safely and efficiently sent to the energy market through the offshore liquefied natural gas (LNG) industry chain, which provides a feasible idea for the utilization, development, storage and transportation of deep-sea natural gas fields. The offshore LNG industry chain includes production equipment (LNG-FPSO, LNG Floating Production Storage and Offloading Unit, also known as FLNG) and receiving equipment (LNG-FSRU, LNG Floating Storage and Regasification Unit). Due to the influence of sea conditions, the key cryogenic heat exchangers in LNG-FPSO and LNG-FSRU have the problem of insufficient heat transfer caused by uneven distribution of multiphase flow, which affects the performance index of liquefaction and gasification process. In this work, the visualization experimental device and numerical simulation model of falling film flow in LNG-FPSO and multiphase flow of intermediate medium in LNG-FSRU have been established, based on the sloshing platform system, camera and processing system, VOF two-phase flow model and dynamic grid technology. The measures are put forward to improve the offshore adaptability of multiphase flow in offshore LNG industry chain. When the anti-sloshing angle of the cover plate is 15°, the liquid fluctuation index (FI) is small and the anti-sloshing resistance is good. The optimal number of transverse anti-sloshing separators is 3, and the anti-sloshing partition number required for unit axial length is 7.5.

CFD modeling and simulation of the hydrodynamics characteristics of packed column with structured sinusoidal corrugated sheets packings

In this study, the hydrodynamics characteristics of packed column with structured sinusoidal corrugated sheets packings were investigated by computational fluid dynamics (CFD) modeling and simulation method. The proposed CFD model was first validated by comparing simulation results with those of experimental data in terms of pressure drop under different inlet gas velocities. Then the effects of wave length, amplitude, angle and placement method on dry pressure drop were studied by control variable method. The relationship between F factor and pressure drop with different packing structures were investigated. The flow fields of pressure and velocity were analyzed and then used to calculate the resistance coefficient of structured packings. This simulation study can contribute to the evaluation and optimization of multiphase flow characteristics and the mass transfer performance of packed column.

Relative permeability of gas and water flow in hydrate-bearing porous media: A micro-scale study by lattice Boltzmann simulation

The water-gas relative permeability is an important parameter to characterize multiphase flow in sediments. To study the water-gas relative permeability of hydrate-bearing porous media, multiphase flow simulations were carried out at the pore scale using the lattice Boltzmann method. The effects of hydrate saturation and hydrate-growth habits on the water-gas relative permeability, which is scaled by the relative permeability considering the hydrate only, were evaluated in a two-dimensional porous medium. Results show that the increase of hydrate saturation causes the decrease of water-gas effective permeability as expected. However, the effect of hydrate saturation on the water-gas relative permeability is different from that of hydrate saturation on the water-gas effective permeability. The water-gas relative permeability increases with the increase of hydrate saturation in the pore-filling case. The water-gas relative permeability decreases with the increase of hydrate saturation in the grain-coating case. The wettability of solid phase has a different effect on the relative permeability of wetting phase and nonwetting phase. The Jamin effect (phase blocking) was observed and may exist in the production of gas from natural gas hydrate reservoirs. This seriously affects the multiphase flow characteristics. The changes of microscale fluid distribution effect the changes of water-gas relative permeability. The relationship between the water-gas relative permeability and the characterization parameters of microscale fluid distribution was analyzed.

Wellbore multiphase flow behaviors during gas invasion in deepwater downhole dual-gradient drilling based on oil-based drilling fluid

Knowledge of wellbore multiphase flow characteristics is important for early gas invasion identification and treatment, especially in oil-based drilling fluid. The wellbore multiphase flow law in downhole dual-gradient drilling (DDGD) is more complex than that in conventional single-gradient drilling. There was no relevant literature report at present. In this paper, considering the synergistic feedback relationship of multiphase flow, interphase mass transfer, and wellbore temperature, a fully transient wellbore multiphase flow model was established based on oil-based drilling fluid in deepwater DDGD. The model also coupled the variable temperature–mass flows caused by the dynamic transfer of hollow glass balls and formation gas. The bubble interface mass transfer theory was adopted to describe the interphase mass transfer rate. The model was verified through the experimental measurement data. The calculated results indicated that the dynamic transfer of hollow glass balls varied the wellbore pressure gradient and flow rate in DDGD, resulting in a sudden decrease in gas fraction and gas solubility along the flow direction at the separator. Additionally, the transient interphase mass transfer and wellbore temperature had large impact on the wellbore multiphase flow behaviors. Moreover, the model based on bubble interface mass transfer theory could more accurately characterize the development of the wellbore multiphase flow. This research could provide a certain theoretical basis for the detection and treatment of gas invasion in deepwater DDGD.

Modeling of multiphase flow during underbalanced drilling considering velocity, temperature and pressure

A clear understanding of multiphase flow with phase change is of great significance in productivity evaluation, process optimization, and production analysis, which is one of the focus issues of underbalanced drilling. In the process of underbalanced drilling, the annular flow is very complex. To drill safely and protect the reservoir, the dynamic separation process of dissolved natural gas and the characteristics of downhole multiphase flow are studied in this paper. Focusing on the characteristics of live crude oil and physical parameters in the wellbore, the authors creatively consider the influence of the velocity on the solubility and establish a mathematical model of multi-physical field non-equilibrium phase change and multiphase flow considering velocity, temperature and pressure. According to the established mathematical model, the solubility diagram of natural gas is drawn, and the evolution law of flow parameters is analyzed. The results show that the influence of the three factors on solubility is that the influence of pressure is greater than that of temperature, and the influence of temperature is greater than that of flow velocity. The effect of flow velocity on annular pressure, temperature and phase content does not seem to be very great in the natural gas solubility model. However, the dissolved gas in the wellbore separates earlier when considering the velocity than when the velocity is not considered. It is concluded that the research presented here confirms that the influence of flow velocity cannot be ignored. The innovative mathematical model in this paper takes into account the effect of flow velocity on non-equilibrium multiphase flow with phase change. By using the model developed, a better understanding can be obtained of what the phase change characteristics of downhole fluid are and how the multiphase flow laws will change, which is of great significance to reservoir protection and drilling safety.

Study of Water Huff-n-Puff in Low-Permeability Oil Reservoirs With Horizontal Fractures: A Case Study of Chang 6 Reservoir in Yanchang, China

Water huff-n-puff is an effective technology to enhance oil recovery (EOR) of low-permeability reservoirs, which are usually developed with hydraulic fracturing. Fluid exchange between fractures and the matrix is the main EOR mechanism. However, the presented water huff-n-puff simulations usually assume vertical fracture morphology, while the horizontal fractures formed in shallow reservoirs are rarely reported. In this study, we first introduced the water huff-n-puff process in a low-permeability oil reservoir with horizontal fractures and described the multiphase flow characteristics during the huff, soak, and puff stages. Then combined with a series of experiments, a comprehensive method is used to determine the key flow parameters, that is, capillary pressure and relative permeability. Finally, using the Chang 6 reservoir as an example, a series of numerical simulations were conducted to demonstrate the effect of water huff-n-puff on the well performance in this field. The simulation results showed that oil production is mainly affected by the injection volume and injection rate, while water production mainly depends on the well shut-in time. For a typical well in this field, the optimal injection volume, injection rate, and well shut-in time are 300 m3, 10 m3/d, and 30 days, respectively. In addition, our results showed that increasing the number of cycles not only benefits fluid exchange but also enhances the formation pressure. Both of them can accelerate the development of low-permeability oil reservoirs.

Investigation of the Water Draining Process Pushed by Gas for U-Type and Z-Type Manifolds

In the experimental advanced superconducting tokamak (EAST), the cooling channels of plasma-facing components (PFCs) are familiarly connected in parallel through manifolds. According to the drainage performance of the PFCs, the amount of water trapped in the cooling channels is directly correlated with the type of manifolds. To date, manifold types have been well studied with respect to single-phase and mixed multiphase flow characteristics. However, there are few studies on the drainage performance relevant to the type of manifolds. The friction effect and inertia effect in the manifold intake and exhaust are studied through theoretical analysis. In addition, the draining liquid effect in the branches is dependent on the pressure difference and the resistance coefficient. Furthermore, U-type and Z-type manifolds are studied with FLUENT to discuss their drainage capability in this study. The distribution of the water volume fraction, pressure, and flow ratio is obtained to verify that the Z type is more effective than the U type when applied in the drainage process. This is also supported by comparing the experimental value of the two in drainage discharge. This study will provide a theoretical basis for future upgrades of EAST drainage systems.

Critical rate analysis for CO2 injection in depleted gas field, Sarawak Basin, offshore East Malaysia

This study aimed to address the challenges and strategies to determine the critical rate of CO2 injection into a carbonate depleted gas field. In this research, the critical rate is the maximum allowable injection rate before formation damage initiation. The cause of formation damage could be due to in-situ mobilization or trapping of migratory fines resulting in plugging the flow path. This study performed a thorough investigation of a different rock-fluid system to evaluate the safe injection limit, as the critical rate is different for each rock-fluid system. The geochemical effect of CO2 injection toward carbonate formation was also investigated in this research. Other than that, the porosity and permeability changes due to CO2-brine-rock multiphase flow characteristics were considered to understand the feasibility of CO2 sequestration into carbonate formation. This research discussed experimental design to mimic the CO2 injection scenario of CO2 into carbonate depleted gas field. Therefore, several core flooding experiments were conducted under reservoir conditions using representative native cores, CO2, and synthetic formation brine. Abrupt changes in differential pressure (ΔP), analysis of effluent collected after CO2 multi-rate flow, and pH reading are the key indicators to consider that the condition has reached a critical rate. The experimental result demonstrated the existence of fines migration, scale formation, and salt precipitation after the core was subjected to supercritical CO2 multi-rate flow. Considering these issues and challenges associated with injectivity, this study recommended a maximum injection rate prior to field scale injection.

Application of CFD Numerical Simulation Image Imaging Technology in the Study of Droplet Microfluidic Multiphase Flow Characteristics.

In order to study the problem that the flow in the internal channel of the microfluidic chip is different from that of the macroscopic system by the FD numerical simulation image imaging technology. Taking the liquid-liquid extraction of microfluidic chip as the research object, this paper analyzes the theoretical basis, working principle, structural parameters, and the influence of working parameters on the fluid flow of liquid-liquid extraction. The results are as follows: when the inlet velocity of flowing liquid is 10^(−5) m/s, the diffusion efficiency can still be maintained at 95%; the double ψ-type aqueous phase showed laminar flow, the two-phase contact interface increased compared with the bottom flow rate, and the extraction efficiency increased to 98%; the extraction efficiency of double ψ type is higher than that of double Y-type: when the flow velocity ratio increases from vaq : voil=1 : 2 to vaq : voil=5 : 1, the extraction efficiency increases to 99.8%; the experimental extraction efficiency is compared with the diffusion efficiency simulated by simulation. The diffusion efficiency of the cross type is 1.05 times that of the extraction efficiency, and that of the cylindrical type is 1.04 times that of the extraction efficiency. In this study, CFD is used to simulate the characteristics of droplet microfluidic multiphase flow, which enriches the theoretical method and research experience of liquid-liquid laminar flow.

Multiphase flow applications of nonintrusive reduced-order models with Gaussian process emulation

Abstract Reduced-order models (ROMs) are computationally inexpensive simplifications of high-fidelity complex ones. Such models can be found in computational fluid dynamics where they can be used to predict the characteristics of multiphase flows. In previous work, we presented a ROM analysis framework that coupled compression techniques, such as autoencoders, with Gaussian process regression in the latent space. This pairing has significant advantages over the standard encoding–decoding routine, such as the ability to interpolate or extrapolate in the initial conditions’ space, which can provide predictions even when simulation data are not available. In this work, we focus on this major advantage and show its effectiveness by performing the pipeline on three multiphase flow applications. We also extend the methodology by using deep Gaussian processes as the interpolation algorithm and compare the performance of our two variations, as well as another variation from the literature that uses long short-term memory networks, for the interpolation.

Enhance flows of waxy crude oil in offshore petroleum pipeline: A review

In the petroleum industry, the transport of offshore crude oil via pipelines may suffer damage known as wax precipitation. This reduces the flow capacity of the crude oil, reducing its transport efficiency. Under extreme conditions, this may also result in serious damage to equipment. To help alleviate this problem, the petroleum transport and flow characteristics of offshore waxy crude oil in pipelines are investigated, together with the development of several options to help minimize wax precipitation. This paper reviews the current research status for reducing wax precipitation and enhancing crude oil flow in offshore pipelines. Specifically, reducing the viscosity of waxy crude oil, strengthening the process technology of the pipeline and the related flow mechanisms are each investigated. This paper also identifies and discusses areas of study that require further investigation. • Offshore crude oil wax deposition is generated by the precipitation of wax crystals in crude oil. • DRAs, PPD, microbial and hydrate inhibitor decrease the viscosity by reducing the generation of wax crystals. • Skin effect electrical heat tracing increase the temperature of pipeline internal to reduce wax deposition. • Inner wall coating reduces the flow resistance of pipe internal to enhance flows of crude oil. • Hernandez Model, Singh Model and Rygg Model describe the multiphase flow characteristics of crude oil in offshore oil pipelines.

The effect of inorganic salt on multiphase flow characteristics in a microbubble column: A focus on the ionic strength

AbstractWith enormous interfacial area for particle collection, microbubbles exhibit great application prospect in the mineral flotation. Under certain ionic strength, microbubbles can be produced continuously in the microbubble column without extra reagent addition. In this work, multiphase flow characteristics (Sauter mean diameter, bubble size distribution, gas holdup & interfacial area) were studied systematically with variables including the salt type, salt concentration, and operating conditions. Based on mathematical model, critical coalescence concentration was determined for each investigated salt. According to experimental results, a mathematical correlation was established between the Sauter mean diameter and ionic strength. For the formation of microbubble system, the lowest ionic strength was approximately 0.5 mol/L. Multiphase flow characteristics in the microbubble column depended highly on the ionic strength. The interfacial area and gas holdup increased by 38 times and more than 3 times respectively, with the ionic strength of Al2(SO4)3 rising from 0 to 1.5 mol/L. The critical coalescence concentration ranged from 0.037 mol/L (Al2(SO4)3) to 0.517 mol/L (NaCl), which correlated with the ionic strength of each salt.

Elongated bubble velocity estimation in vertical liquid-gas flows using flow-induced vibration

The multiphase flow occurs in various major industrial fields and nature. Furthermore, due to the single and multiphase flow characteristics, they generate vibration on the structure conveying or subjected to the flow. This paper investigates in an experimental apparatus, the possibility to use the flow-induced vibration from a vertical liquid-gas two-phase flow conveyed by a pipe to obtain the elongated bubble velocity. The vibration signal analysis in time domain showed that the structural excitation due to the elongated bubble rising in the stagnant liquid was significant to be distinguished from other excitations. The time-frequency analysis of slug and churn flow showed a significant amplitude variation in a specific frequency band. Finally, it was possible to obtain the elongated bubble velocity with reasonable accuracy by cross-correlating the envelope of a vibration signal filtered in a particular frequency band of two accelerometers. Thus, this paper presents a non-invasive and simple to mount technique to estimate the elongated bubble velocity in stagnant and moving liquid conditions.

Variation in Multiphase Flow Characteristics by Nozzle‐Twisted Lance Blowing in Converter Steelmaking Process

A 3D gas–slag–metal model for a 120t converter with nozzle‐twisted lance is established, and the gas jet characteristics, slag–metal interface fluctuations, wall erosion, and changes in the molten pool flow field of the nozzle‐twisted lance of the blowing process are studied. The results reveal that, with the increase in the swirl angle, the length of the jet high‐velocity section, maximum velocity, and dynamic pressure decrease, radial distance increases, and wall shear stress first decreases and then increases. With an increase in the blowing time, the fluctuating intensity of the slag surface and the molten steel surface changes significantly, fluctuating slag surface stabilizes after 1.7 s (fluctuating intensity is 1.08–1.12), and fluctuating steel surface stabilizes after 1.3 s (fluctuating intensity is 1.23–1.33). The turbulent kinetic energy of the gas–slag–metal three‐phase interaction area increases and the wall shear stress gradually increases.

A CNN-based approach for upscaling multiphase flow in digital sandstones

In digital rock physics, finding the trade-off between image resolution and field of view and, at the same time, maintaining the accuracy of flow prediction in a low-resolution large-scale model is a challenging task. Multiphase flow characteristics are strongly dependent on image resolution. Therefore, the upscaling process based on pore-scale simulations is crucial for predicting low-resolution model properties regarding the referred trade-off.This study has disclosed an upscaling method taking advantage of convolutional neural networks (CNNs) and downsampling techniques. The method has been applied to a set of multi-scale images taken from Fontainebleau sandstone. High-resolution images are downsampled and then labelled with their properties to train CNNs. Trained CNNs are then used to predict the upscaled properties of low-resolution samples. The predicted upscaled properties by CNNs are assigned to computational grids of the reconstructed low-resolution model in a continuum-scale simulator. By performing multiphase flow simulations of the mentioned model and various assigned properties, the resultant dynamic behaviours from low-resolution and CNN upscaled properties are compared with the dynamic behaviour of the high-resolution case. Results showed a satisfying match between the dynamic behaviour of the upscaled model through CNNs and high-resolution properties with a significant reduction of computational cost and time.

Experimental investigation on the multiphase flow characteristics of oblique water entry of semi-closed cylinder

The multiphase flow characteristics of the oblique water entry of semi-closed cylinders is investigated experimentally. The results from the experiment are used to analyze the flow mechanism and to validate the numerical simulations. In the experimental setup, a high-speed photography technique is used to capture the process of water entry based on digital video images. It can be observed that the cavity is formed in three (3) flow modes namely the fluctuation cavity, the transition cavity, and the blurry rippling cavity. The transparency of the cavity surface decreases, while the fragmentary and blurry rippling increases, with an increasing inclined angle of the cylinder. Owing to the instability of internal flow structure and the degree of cavity closure, the cavities of three (3) flow modes occur in sequential order from clear fluctuant cavity, rippling fluctuant cavity, to continuous blurry and fragmentary ripples. The cavity evolution is also found to affect the structure of multiphase flow field and the dynamic characteristics of semi-closed cylinder.

Characterization of flow units, rock and pore types for Mishrif Reservoir in West Qurna oilfield, Southern Iraq by using lithofacies data

This study has been accomplished by testing three different models to determine rocks type, pore throat radius, and flow units for Mishrif Formation in West Qurna oilfield in Southern Iraq based on Mishrif full diameter cores from 20 wells. The three models that were used in this study were Lucia rocks type classification, Winland plot was utilized to determine the pore throat radius depending on the mercury injection test (r35), and (FZI) concepts to identify flow units which enabled us to recognize the differences between Mishrif units in these three categories. The study of pore characteristics is very significant in reservoir evaluation. It controls the storage mechanism and reservoir fluid properties of the permeable units while pore structure is a critical controlling factor for the petrophysical properties and multiphase-flow characteristics in reservoir rocks. Flow zone indicator (FZI) has been used to identify the hydraulic flow units approach (HFUs). Each (HFU) was reproduced by certain FZI and was supposed to have similar geological and petrophysical properties. The samples were from four lithofacies, mA, CRII, mB1, and mB2. Because of the wide range of cored-wells samples (20 wells), this paper is updated the previous studies and indicated some differences in the resulting categories. It was noticed as results of this study that the rocks types of the lower Mishrif were mostly ranged from wackestone to packstone in the upper part of mB2 which reflected mid-ramp facies while the upper part of mB2 referred to shoal facies and for the mB1 unit the rocks types mostly range from packstone to grainstone with some points as wackestone marked as shoal and rudist bioherm facies. Grainstone relatively decreases with the increasing of depth from upper to lower Mishrif while wackestone and packstone indicated increasing in the same direction. The unit mA is marked as mesopores and macropores, while megapores and macropores feature increased in mB1 which has been noticed in the northern part of West Qurna oilfield due to increasing shoal and rudist bioherm facies, the mB2 unit revealed increasing in mesoporous and decreasing in megaporous. The upper Mishrif (mA) has three flow units, while the lower Mishrif (mB1, mB2) has eight flow units four for each reservoir unit.

Particle Motion Characteristics in W-Shaped Hydrocyclones

To investigate the multiphase flow characteristics and improve the classification mechanism of a W-shaped hydrocyclone, this paper adopts the numerical simulation method to evaluate the effects of the particle size and density on the separation characteristics and motion behavior of particles. Forces, such as the centrifugal inertia force, pressure gradient force and fluid drag force, which control particle motion, are analyzed, and the classification mechanism of W-shaped hydrocyclones is examined in terms of the particle distribution and separation efficiency. The results indicate that the radial centrifugal inertia and pressure gradient forces in W-shaped hydrocyclones are hundreds of times the gravity force, which is the main driver of radial motion. Particle density and size changes greatly impact the movement and distribution of coarse particles, but no notable change occurs in fine particles. With increasing particle density, the cut size decreases, and the fractionation accuracy increases.