Two-phase Flow In Horizontal Pipe Research Articles

Slug flow characteristics of air-liquid two-phase flow in horizontal pipes over a wide range of liquid viscosities

A large number of studies have been conducted to understand the slug flow characteristics of air-liquid two-phase flow in horizontal pipes and to capture parametric trends of critical flow parameters associated with slug flow, such as the liquid slug length, elongated bubble length, and elongated bubble velocity. Based on these findings, many attempts have been made to develop empirical correlations to predict the slug flow parameters. However, the validity of these correlations is limited to a specific working fluid and narrow ranges of geometrical or operating conditions, thereby reducing their effectiveness as useful general predictive tools. This limitation has created a need to develop empirical correlations that offer high accuracy over a broad application range, i.e., a wide range of liquid viscosities, superficial liquid and gas velocities, and pipe diameters. In this study, two-phase slug flow experiments were performed to examine the hydrodynamic features of slug flow under two different pipe diameters (2 and 4 cm) and two different liquid temperatures (25 and 45°C). In addition, a new consolidated database consisting of 1563 slug flow data points was amassed from 16 sources, including the present experimental data, covering a wide range of operating conditions and fluid properties. In particular, this study includes various liquids with a wide range of viscosities, such as heavy oil, light oil, and water. The parametric study of air-liquid slug flow at various viscosity levels revealed that as the mixture velocity increases, the liquid slug length tends to decrease when the liquid viscosity is high and increase when the liquid viscosity is low. On the other hand, the elongated bubble length and elongated bubble velocity increase with increasing superficial gas velocity, regardless of the liquid viscosity. Based on these findings, three empirical correlations were developed to predict the liquid slug length, elongated bubble length, and elongated bubble velocity. These correlations provide excellent predictive capability against the consolidated database, with overall MAE values of 18.1%, 20.6%, and 9%, respectively.

Sparse Local Fisher Discriminant Analysis for Gas-Water Two-Phase Flow Status Monitoring With Multisensor Signals

Gas-water two-phase flow has typically stable flow statuses and constantly changing transition flow statuses. Accurate identification and real-time monitoring of flow status are conducive to the in-depth study of two-phase flow and the safe operation of industrial process. A monitoring strategy based on sparse local Fisher discriminant analysis (SLFDA) is proposed in this article. First, multisensor signals are obtained to reflect flow process information. Second, the least absolute shrinkage and selection operator is used to find the sparse discriminant directions to determine the key variables relevant to the flow process from multiple sensor signals. Then, the weight coefficient matrixes of SLFDA keep the original structure of the same flow status data and make the data of different flow statuses more separated, which distinguish different flow statuses to the maximum extent. Finally, two monitoring indexes including the discriminant index and the stability index are established to analyze the dynamic flow process, which enable a concurrent monitoring of both flow evolution and instability to realize fine-scale description of flow process. SLFDA can monitor various flow statuses through only one projection discriminant matrix by transforming high-dimensional signals into features representing the flow characteristics, which avoids model traversal and improves monitoring efficiency. Further study of flow status features provides meaningful physical interpretation and in-depth process analysis with consideration of actual flow process. The application on the data of gas-water two-phase flow in horizontal pipe demonstrates the feasibility and efficacy of the method.

NOVEL MODEL FOR ESTIMATING GAS-SOLID TWO-PHASE FLOW RATE IN A HORIZONTAL PIPE

Dilute and dense conveying systems through pipelines are a common practice in our everyday life. It is used in many industries to convey a mixture of gas and solids from one location to another through pipes. Gas-solid transport is desirable in some industries but unwanted in others. Depending on the density, size, and shape, these solid particles may result in erosion and subsequent damage to piping and other equipment. Understanding the gas-solid two-phase flow dynamics can help develop efficient and cost-effective pipe transport systems, thereby mitigating the problems associated with the gas-solid two-phase flow. Models for estimating volumetric flow rates and other gas-solid two-phase flow properties are scarce as most are very complex, expensive, and unavailable proprietary commercial software. This study, therefore, developed a simple model using the general energy balance equation and relevant mixing theories for estimating the volumetric flow rate of natural gas-solid two-phase flow in horizontal pipes. The results from the model showed that the gas-solid flow rate is a function of pipe diameter, pressure drop, pipe length, solid volumetric concentration, solid-to-gas density ratio, and solid-to-gas friction factor ratio.

Concentration Profile Measurement of Liquid–Solid Two-Phase Horizontal Pipe Flow Using Ultrasound Doppler

Concentration measurement of multiphase flow is essential to flow assurance and monitoring in industrial processes. The concentration profile is a quantitative parameter to diagnose the multiphase flow states and has drawn wide attention from researchers. An ultrasound Doppler technique is adopted to measure the concentration profile of liquid-solid two-phase horizontal pipe flow. A Bayesian inference based on the Differential Evolution Adaptive Metropolis sampling algorithm is proposed to solve the statistical inversion of the concentration profile. The posterior probability distributions of the solid concentration are sampled, and the final concentration profile is chosen with the maximum a posteriori probability. An experimental platform is built for liquid-solid two-phase flow experiments and ultrasound concentration profile measurement. The measured concentration profiles are verified with a maximum mean absolute error of 8.14%.

水平管内气液两相流流固耦合动力响应特性的数值研究

水平管内气液两相流流固耦合动力响应特性的数值研究

Flow Regime Identification in Gas-Liquid Two-Phase Flow in Horizontal Pipe by Deep Learning

Two phase flow commonly occurs in industrial pipelines, heat exchangers and nuclear power plants. A characteristic feature of two-phase flow is that it can acquire various spatial distribution of phases to form different flow patterns/regimes. The first step to successfully design, analyze, and operate gas-liquid system is flow regime identification. Flow regime identification is of huge importance to the effective operation of facilities for the handling and transportation of multiphase fluids, and it represents one of the most significant challenges in petrochemical and thermonuclear industries today. The objective of this study is to develop a methodology for identification of flow regime using dynamic pressure signals and deep learning techniques. Three different flow regimes were simulated using a Level-Set (LS) method coupled with Volume of Fluid (VOF) method in a 6 m horizontal pipe with 0.050 m inner diameter. Dynamic pressure readings were collected at a strategic location and were converted to scalograms to be used as inputs in deep learning architectures like ResNet-50 and ShuffleNet. Both architectures performed effectively in classifying different flow regime and recorded testing accuracies of 85.7% and 82.9% respectively. According to our knowledge no similar research has been reported in literature, where various Convolutional Neural Networks are used along with dynamic pressure signals to identify flow regime in horizontal pipe.

Effects of rolling motion on transient flow behaviors of gas-liquid two-phase flow in horizontal pipes

The investigation of transient flow behaviors of gas-liquid two-phase flow under ocean conditions is vital to the application of gas-liquid transport in ocean engineering area. In this paper, the gas-liquid two-phase flow numerical model of rolling horizontal pipe is established based on CFD code combined with user-defined functions (UDF). The three-dimensional rolling flow fields are simulated using the volume of fluid (VOF) model, RNG k−ε turbulence model and additional inertia force method. First, the simulation results are compared with the experimental data, which revealed a reasonable agreement. Then, the variation in transient flow behaviors by horizontal pipe (L = 2.0 m, D = 0.035 m) with varying rolling conditions (θm = 2°-6°, T = 0.5–4.0 s) and flow velocities (jG = 0.1–10.0 m/s, jL = 0.1–0.5 m/s) are investigated. The results showed that the rolling motion caused agglomeration of dispersed bubbles and gas slugs into a continuous gas column, increased the cross-sectional void fraction significantly. The variation of additional inertial force and pressure drop increased with the increase of rolling angle and the decrease of the rolling period. Compared with the rolling angle, the transient flow behaviors are more sensitive to the rolling period. In addition, as the initial gas volume fraction increased, the effects of rolling motion on the transient flow behaviors decreased gradually. These qualitative conclusions may serve as a reference for gas-liquid transport simulations under rolling conditions.

Detection and optimization of viscous oil viscosity and vissity reducer in alx gas well

The optimum viscosity of heavy oil is the key index to maintain the normal production of gas wells. This paper designs a new detection and optimization method of visit oil visibility and visibility reducer in alx gas well. Firstly, through the flow pattern criterion and flow pattern distribution diagram of gas-liquid two-phase flow in horizontal pipe, the propagation velocity of wave in the downstream is determined by extreme value method, and the maximum viscosity equation of heavy oil carried by air in annular fog state is established. Then, according to the maximum viscosity equation, the maximum viscosity of the heavy oil carried by the gas flow is 513.7 MPa. Finally, taking alx gas well as an example, 11 kinds of viscosity reducer were selected from water-based viscosity reducer and oil-based viscosity reducer. Under the conditions of wellhead temperature of 9 ° C and bottom hole temperature of 34 ° C, five samples with different concentrations were mixed with heavy oil, the rheological properties of the sample set were tested, and the rheological parameters and apparent viscosity of heavy oil were calculated. The experimental results show that low dosage of oil-based tackifier can effectively reduce the viscosity of heavy oil, and the optimal dosage range is 22% to 25%.

All-regime two-phase flow modeling using a novel four-field large interface simulation approach

Two-phase flows may occur in many regimes, ranging from dispersed flow, slug or plug flow to stratified flow. To capture all those regimes with a monolithic approach, a so-called all-regime two-phase model should be developed. This paper presents such an all-regime two-phase modeling approach called Four-Field Large Interface Simulation (FF-LIS), in which we consistently consider two phases (gas and liquid) which can both be either resolved or sub-grid, resulting in four fields. The efficacy of this approach hinges on the accuracy with which the inter-scale mass, momentum and energy transfer terms between dispersed and resolved regimes are captured. In this paper, we introduce three phenomenological mechanisms to control the inter-scale transfer: absorption, break-up and coalescence. The separation of multiphase scales allows for the explicit modeling of transfer between them, whereas other methods often rely on an algebraic regime map in which transfer between scales is accounted for implicitly. We apply FF-LIS to the simulation of both bubbly and fully resolved single bubble flow, as a way of validating FF-LIS in those two two-phase limits. Next, the transfer terms are illustrated by simulation of bubbles rising in a column. As the bubble concentration increases, it is shown that a transfer from sub-grid to resolved occurs. Finally, we apply FF-LIS to the simulation of two-phase horizontal pipe flow in which the several flow regimes, depending on the superficial velocities, are recovered, and to the simulation of a plunging jet in which FF-LIS is shown to produce an entrained bubble plume. FF-LIS presents a computational platform for faithful two-phase resolved and sub-grid simulation of relevant real-world two-phase problems, and allows two-phase modelers for the explicit control on what can be resolved, and what should be sub-grid.

Numerical investigation of gas-liquid two-phase flow in horizontal pipe with orifice plate

Gas-liquid two-phase flow in horizontal or vertical pipeline significantly impacts on the transportation process. In fact, in the pipeline for regulating the flow flux or pressure, orifice plate and other current limiting device are frequently encountered. The flow behaviors of two-phase flow thus become more complicated in the pipeline with orifice plate. In order to explore the characteristics of gas-liquid two-phase flow in the pipeline accompanied by orifice plate, the computational fluid dynamics (CFD) simulation with volume of fluid (VOF) method and SST k−ω eddy viscosity model were imposed to probe the transient two-phase flow in a horizontal pipeline. The reliability of the numerical method was verified by a case of annular multiphase flow in a pipeline. In our research, two transient simulations related to different liquid volume ratios were carried out to explore the developments of the flow regimes. In addition, fluctuations of the area-average fluid pressures acting on the orifice plate surfaces were also monitored. The frequency characteristics of pressure pulsations were extracted via non-uniform fast Fourier transform (NUFFT). The main results show that the jet could be produced after the liquid passes through the orifice plate, and the liquid volume ratio has significant effects on the gas-liquid two-phase flow behaviors, a higher ratio leads to a faster stable and fuller jet. The stability of jet could be reflected via the dimensionless velocity ratio. The gas-liquid two-phase flow in the pipe with orifice plate induces typical broadband excitation.

Analysis of interfacial behavior in two-phase flow using image processing

Two-phase flow has a wide range of application from petroleum to space industry. Gas-liquid two-phase flow in horizontal pipe commonly occurs in petro-chemical, nuclear and geothermal industry, where simultaneously gas and liquid are transported through pipelines. During the transportation of gas-liquid flow simultaneously, due to the interaction of two phases, slug forms from the stratified-wavy flow. Slug flow consists of strong aeration at the slug front which is responsible for pipe failure and hazards in industries. Thus, it is required to understand the phenomena of slug formation in industrial pipeline to avoid the catastrophic pipe failure. In the present research, image processing technique is used to accurately analyze the interfacial behavior of two-phase flow. The interfacial behavior plays crucial role, as it is the plane where the two phases interact and interaction of the phases leads to the transition of different two-phase pattern. Experimentally captured images are processed using image processing algorithm, to study the variation of liquid film thickness. With the help of liquid film thickness transition of the interface is analyzed for different superficial Reynolds number of liquid and gas. Further, a PDF analysis is reported to understand the mechanism of the growth of the wavy interface.

Effects of density, viscosity and surface tension on flow regimes and pressure drop of two-phase flow in horizontal pipes

Two-phase gas/liquid flow in pipes is a common occurrence in the petroleum, chemical, nuclear and geothermal industry. In the petroleum industry, it is encountered in the production, transportation, and processing of hydrocarbons from the oil and gas fields. In designing these systems, accurate prediction of pressure drop is imperative, which is determined from the flow pattern and flow regime map. Unfortunately, most of the flow regime maps were developed for the air-water system and widely used for the oil/gas system. Despite the practical importance, the general applicability of these maps is not addressed. In order to improve the generality of flow regime maps, it is necessary to evaluate the effect of density, viscosity, and surface tension, which differ by great magnitude on flow regime maps. Thus, this study evaluates the effect of density, viscosity, and surface tension on the flow regime map. To evaluate the effect of fluid properties, experiments were conducted using a horizontal flow loop of 9.15 m (30 ft) pipe length and 0.0254 m (1-inch) pipe diameter with a two-phase air/liquid system. The surface tension was varied using the surfactant solution, viscosity was varied with the aid of glycerin, and density was varied with the aid of calcium bromide. The superficial velocity of the liquid ranges from 0 to 3.048 m/s (0–10 ft/s) and superficial gas velocity ranges from 0 to 18.288 m/s (0–60 ft/s) respectively. The experimental data were used to generate a flow pattern map and to predict the effect of these properties on the variation in the boundaries of different flow patterns and pressure drop. The results show that the flow patterns and transition boundaries were affected by fluid properties. The boundary between the annular and slug-annular flow at high velocity, the slug flow and pseudo-slug flow at medium velocity, and inertial wave and ripple wave flow at low velocities are affected by the variation in surface tension, viscosity, and density. The decrease in surface tension shifted the boundary between annular and slug flow toward the left-bottom corner of the flow regime map, while, similar effects were observed due to an increase in viscosity, which is opposite to the effect of surface tension. The increase in density shifts the boundary toward the top-right corner of the flow regime map. The effect of density on the flow pattern transition is significant compared to the viscosity, while the viscosity effect is higher than the surfactant. The effect of fluid properties on pressure drop is noticeable at high velocities, however, the pressure drop is not evident to reveal the flow pattern and boundary transition quantitatively.

Investigations on the slug two-phase flow in horizontal pipes: Past, presents, and future directives

Precise prediction of the gas–liquid slug flow is crucial for proper design and operation at various industrial processes. This paper provides a comprehensive review of published experimental and numerical works in horizontal pipes, including a critical analysis of state-of-the-art parameters used to characterize the slug flow regime. The discussed slug characteristics are slug length, slug frequency, and slug velocity. Throughout the paper, an endeavor does devote to discerning the areas where modern development work is needed. Accordingly, some observed gaps in the literature, comprising hydrodynamic behavior at the transition zone and the interaction between slug flow and structural pipe. The lack of comprehensive laboratory experimental information for high liquid viscosity and the viscosity impact on the slug characteristic is also observed. On the contrary, robust and less empirically independent CFD models are required for accurately predicting the slug characteristics with a minimal computational cost.

Flow status identification based on multiple slow feature analysis of gas–liquid two-phase flow in horizontal pipes

A gas–liquid two-phase flow is a highly complex and random process with complicated and variable flow statuses. The status identification of two-phase flows focuses on the situation of flow processes over specific time periods, as reflected by flow regimes, phase holdup, flow velocity, and other parameters. Aiming to discover how to obtain flow status information and identify the flow statuses of gas–liquid two-phase flows in horizontal pipes, a meticulous identification method based on multiple slow feature analysis combined with Bayesian inference is proposed, with concurrent monitoring of steady states and process dynamics. In this method, representational models for different typical flow regimes are established to describe both the steady states and temporal distributions. On this basis, by monitoring statistics and developing a Bayesian inference-based index, the current flow status can be identified online. Besides status identification, process dynamics are monitored to detect the dynamic characteristics of the current process with meaningful physical interpretation and deep process understanding. The application of this method to typical flow regimes and the status of transitions from bubble flow to slug flow demonstrates the feasibility and efficacy of the proposed method.

Flow Regimes Identification-based Multidomain Features for Gas–Liquid Two-Phase Flow in Horizontal Pipe

Accurate flow regimes identification is of great significance for the deep understanding of the flow structure and ensuring the safe and economic operation of actual production in the multiphase flow process. For the flow regimes identification of the gas-liquid two-phase flow in the horizontal pipe, a multidomain features processing scheme is proposed. The water holdup data are acquired by conductance rings sensor, and processed by the improved empirical wavelet transform (EWT) to obtain the Fourier spectrum in the frequency domain and decomposition components in the multiscale domain. The obtained multidomain feature information is quantified to get the high-dimensional feature vectors of different flow regimes. To make the features more representative and realize the visualization of the structural relationship between the flow regime samples, the isometric feature mapping (Isomap) method in manifold learning is used to synthesize the feature structure relationships and map them to low-dimensional space. The obtained low-dimensional feature vectors of training samples are input into the support vector machine (SVM) to acquire the flow regimes identification model. Compared with other flow regimes identification schemes that feature reduction uses different manifold learning methods, or feature extraction is not in multidomain, or data preprocessing uses traditional wavelet transform, the proposed scheme can better retain the global structural relationship of the flow regimes, has the characteristics of strong stability, and the identification rate of the gas-liquid two-phase flow regimes in the horizontal pipe is over 95%.

Experimental and Theoretical Study of Interface Characteristics of Gas–Liquid Stratified Flow in Horizontal Pipe at High Pressure

Wave stratified flow is widely encountered in processing industry, the interface wave impacts heat and mass transfer between the fluids, and flow pattern transition from it to slug flow makes it difficult to deal with the processing fluids that transported by long pipelines especially. Meanwhile, the interface wave influences the viscous drag forces working on the fluids in the pipe, which is impacted by the characteristics of interface profile, such as wave length, amplitude and propagation speed. Experiment of air–water two-phase flow in horizontal pipe at different pressures (0.1 MPa, 2 MPa) are carried out, the influence of pressure on interface profile characteristics is studied, new models for wave length, amplitude, frequency and propagation speed are proposed and tested, and good performance is proved. Shear stress working on interface wave is theoretically calculated, influence of both fluids superficial velocities and pressure on it are studied, and its influence on wave propagation speed is formulated.

Correcting interface turbulence viscosity using CFD modeling for predicting stratified gas–liquid flow shear stress in horizontal pipes

Abstract The prediction of different shear stresses is one of the great challenges of turbulent–turbulentstratified two-phase flow in horizontal pipes. In this work, VOF method, near-wall differential viscosity and local turbulence viscosity distribution coefficient function are introduced and offer an efficient tool to correct the interface turbulence viscosity. The results show that the new method can better predict the shear stresses, liquid holdup and pressure drop of stratified two-phase flow. The fitting relationship between interfacial and wall friction factor ( f i ∕ f W ) is in good agreement with the experimental data. It is found that f i ∕ f W is predicted with a relative error of 12.62% by the new method, which is much less than that by any other method when the gas and liquid superficial Reynolds numbers are 8000 ≤ Re S G ≤ 90000 and 5000 ≤ Re S L ≤ 170000. It provides a reliable method for achieving the closure of stratified flow to predict the shear stresses.

Experimental study of gas-liquid two-phase wavy stratified flow in horizontal pipe at high pressure

The regimes of gas-liquid two-phase flow in horizontal pipe at high pressure were experimentally investigated, and characteristics of wave stratified flow, such as wave length, wave height and propagation speed were calculated. The pressure drop was analyzed and friction factors, such as gas-wall, liquid-wall and interfacial friction factors, were calculated and new correlations were deduced. Influence of interface wave on interfacial friction factor was studied, and characteristics of interface wave were included to deduce new correlation for it, and good accuracy was proved. For the gas-water two-phase flow at 2 MPa, transition from wave stratified to annular flow appears with smaller gas superficial velocity compared with that at atmosphere, and intermittent flow appears with greater liquid superficial velocity. Regime transition models are tested, for the gas-liquid two-phase flow at atmosphere the sheltering coefficient with value of 0.01 is appropriate. However, it is promoted to be 0.06 at 2 MPa, and good performance of regime transition model was reached.

Experimental study on the hydrodynamic behavior of gas-liquid air-water two-phase flow near the transition to slug flow in horizontal pipes

The knowledge of the slug flow is essential the design safety of hydrocarbon transportation in the pipeline system of petroleum industries. However, the suitable models to predict the transition condition to slug flow are limited due to insufficient availability of experimental data. In the present study, the hydrodynamic characteristics of the near the transition to slug flow of air-water two-phase flow in horizontal pipes were investigated experimentally for inner pipe diameters of 16 mm, 26 mm, and 50 mm. The superficial velocities of water and air ranged from JL = 0.03 to 0.30 m/s and JG = 0.7 to 10.0 m/s. The hydrodynamic behavior was obtained from the combination of the visualization detected by using a high-speed video camera, the pressure gradient, and instantaneous volumetric liquid fraction measurements.The experimental results indicate that the wave growth and the wave coalescence are involved in the mechanism of the slug flow formation. Both gas and liquid superficial velocities have a significant effect also of those mechanisms. The average volumetric liquid fraction near the transition to slug flow is not affected by superficial gas velocities. Next, under a constant superficial gas velocity, an increase in the inner pipe diameter requires a larger superficial liquid velocity to change the flow patterns from stratified smooth to slug flow, and from pseudo-slug to slug flow.

Experimental investigation of airflow above waves in a horizontal pipe

We investigate the effect of waves on the airflow in horizontal two-phase pipe flow. Velocity fields in the gaseous phase were acquired by particle image velocimetry (PIV), while interfacial elevation was measured with conductance wave probes. The velocity fields were sampled on a wave-following coordinate system which allows for a decomposition of the velocity field into a mean, wave-coherent and fluctuating component by means of a three-component Reynolds decomposition. Additionally, coherent vortical structures were identified by the swirling strength criterion, and their distribution along the waves is investigated.Results suggest that the interaction between turbulent airflow and propagating waves in a pipe has a number of features reminiscent of wind-wave interaction in open systems. Above waves generated by sufficiently high gas flow rates, there is a distinct region of sheltered airflow, and a lifting of the critical layer on the leeward side of the crest. Streamlines of the phase-averaged flow field show a cat’s eye structure located close to the crest in this region. Above waves of moderate steepness, we observe a shear layer that remains adjacent to the wave surface. Above steeper waves and higher gas flow rate, this layer detaches from the surface just downstream of the crest. Shear layer separation above waves is traditionally linked to the onset of wave breaking, and it is interesting to note that the case where we observe a separated shear layer in the phase-averaged vorticity field is in a regime of amplitude saturation.The swirling strength criterion reveals that vortical structures are shed from the interface and populate the detached shear layer above the trough. Below the detached shear layer, there is a region populated by counter-rotating vortices. The critical height coincides with the border between these two regions.