Flow In Vertical Pipe Research Articles

Gas-liquid vertical pipe flow patterns convolutional neural network classification using experimental advanced wire mesh sensor images

Flow pattern identification for simultaneous gas-liquid flow in pipes is a central problem in the petroleum industry. However, there are many conventional methods used for flow patterns identification that come with some form of restrictions limited to specific operating conditions. Although previous studies made efforts to make flow patterns identification free from biases (subjectivity), objective predictions are yet to be fully explored. For the first time, this study employs a 4-layer convolutional neural network (CNN) architecture and threshold segmentation algorithm to classify industrial working fluids of air/silicone oil flow patterns in a vertical pipe. Also, an advanced wire mesh sensor (WMS) instrumentation was used to obtain the cross-sectional frame images from a series of 52 experimental runs. This study made an attempt to use the sequential cross-sectional frames original data obtained from the experimental WMS because it is the crossing wires of the WMS that interact with the flow field and also capture the main flow pattern transitional zones. The obtained experimental testing results indicate that the supervised CNN model has an accuracy of 99.90% better than the seven-benchmarked supervised machine learning classification models used in recognizing bubbly, slug and churn flow patterns. The CNN model experimental test accuracy also outwits other related flow patterns identified in the literature when compared, thereby affirming the model's robustness. Since the WMS provide high spatial and temporal resolutions data, the average pixel intensity values from the segmented images were used as the flow indicator in identifying the transition zones within the main flow patterns. Furthermore, the Locally Interpretable Model-agnostic Explanation (LIME) algorithm for the first time was used to explain and interpret features in the WMS flow images that were contributing to the overall CNN classification scores. Finally, the CNN trained model was able to classify the main flow patterns and segmented transitional zones with certainty and confidence without subjectivity which is inherent in the direct conventional methods.

Measurement of Oil–Gas–Water Flows in Vertical Pipes Using Electromagnetic Flowmeter and Dual-Conductance Sensors

Three-phase flows are significantly complicated in comparison to single-phase flows and gas–liquid two-phase flows. So far, faced with the presence of two nonconductive dispersed phases in oil–gas–water three-phase flows, the measurement characteristics of electromagnetic flowmeter (EMF) in three-phase flows are an unresolved problem. The flowrate of three-phase flows is difficult to measure due to the nonuniformity arising from interactions between dispersed phases. Aiming at the difficult problem of production logging in oil wells of three-phase flows, this article reports an experimental study on measuring three-phase flows via the EMF and the dual-conductance sensors. Among them, the phase holdups of three-phase flow in vertical pipe are extracted through newly designed distributed coaxial double-ring conductance sensor (DRCS) and rotating electric field conductance sensor (REFCS). A three-phase flow loop test in a pipe of 20 mm inner diameter is carried out. The results show that the EMF has the ability to substantively measure the flowrate of water phase under three flow patterns (bubble, slug, and churn flows) when the water cut is above 60%, and the average absolute percentage deviation (AAPD) for prediction of superficial water velocity is 3.55%. The measurement of superficial gas and oil velocities is implemented by solving the drift-flux models of three-phase flow based on the phase holdups and superficial water velocity, and the AAPDs for predictions of superficial gas and oil velocities are 4.33% and 5.95%, respectively. This research provides a new measurement strategy for production logging of oil, gas, and water three-phase flow production profile by combining the EMF with dual-conductance sensors.

Mechanistic modeling of flow and heat transfer in vertical upward two-phase slug flows

Two-phase slug flow exhibits intrinsically stochastic and statistically periodic flow behaviors. Understanding the mechanisms of flow and heat transfer of upward two-phase slug flow is important. This paper develops a mechanistic model of flow and heat transfer for upward two-phase slug flow in vertical pipes. First, a hydrodynamic model of two-phase slug flow in regular-sized channels is developed based on the hypothesis of the slug unit cell. Each slug unit cell is hypothesized to be composed of a liquid slug and a Taylor bubble region. Second, a mechanistic heat transfer model is derived based on the hydrodynamic model. The overall heat transfer coefficient is integrated by using the local heat transfer coefficients of liquid slug and the Taylor bubble region. Third, the proposed mechanistic model is validated by the experimental void fraction, pressure drop, and two-phase heat transfer coefficient from different sources. Finally, the effect of flow geometry and parameters—such as superficial gas and liquid velocities, void fraction, slug frequency, pressure drop, and the ratio of slug length to unit cell length—on heat transfer in two-phase slug flow is comprehensively investigated. The enhancement in heat transfer in two-phase slug flow compared with that of single-phase flow can be attributed to an increase in the turbulence of the liquid due to the injection of air and a reduction in the thermal boundary layer owing to the frequent alternation between liquid slug and the Taylor bubble.

Computational case study on upward two-phase flow in vertical circular pipe based on CFD approach: Multidimensional flow instabilities investigation

In this paper, a numeric scheme made up of the three-dimensional (3-D) Two-Fluid Model (TFM) and the Rensselaer Polytechnic Institute (RPI) wall boiling model for two-phase flow instabilities simulation was validated by comparing its results with the flow boiling and instability experimental data. Then two-phase flow instabilities in a vertical circular channel were studied based on the validated numeric scheme. The flow instability was analyzed by both the Lumped Parameter Approach (LPA) and the Distributed Parameter Approach (DPA). The average parameter oscillation characteristics and local distributions were analyzed. The transient responses of the local conditions during the flow instability were discussed. Besides, the stability of the vertical circular tube channel flow boiling system was studied with the stable map based on the subcooling number (Nsub) versus the phase change number (Npch). This study provides a new feasible scheme for the simulation of flow instability which also actualizes an improved understanding of multidimensional flow and heat transfer characteristics in the flow instabilities phenomenon.

Ultrasonic Measurement for the Experimental Investigation of Velocity Distribution in Vapor-Liquid Boiling Bubbly Flow

This study proposes an ultrasonic velocity profiler (UVP) with a single ultrasonic gas-liquid two-phase separation (SUTS) technique to measure the velocity distribution of vapor-liquid boiling bubbly flow. The proposed technique is capable of measuring the velocity of the vapor bubble and liquid separately in boiling conditions. To confirm the viability of the measurement technique, the experiment is conducted on vertical pipe flow apparatus. The ultrasonic transmission and effect of ultrasonic refraction through the pipe wall and water are investigated at ambient temperature until subcooled boiling temperature is reached. The velocity profile in the water at elevated temperature is measured to verify the ability of the technique in this application. The bubbly flow velocity distribution measurement in boiling conditions is then demonstrated. The results show that the proposed technique can effectively investigate the velocity of both phases under various fluid conditions in boiling bubbly flow.

Exact solutions for steady granular flow in vertical chutes and pipes

Vertical chutes and pipes are a common component of many industrial apparatus used in the transport and processing of powders and grains. Here, a typical arrangement is considered first in which a hopper at the top feeds the chute and a converging outlet at the bottom controls the mass flux. Discrete element method (DEM) simulations reveal that steady uniform flow is only observed for intermediate flow rates, with jamming and unsteady waves dominating slow flows and non-uniform wall detachment in fast flow. Focusing on the steady uniform regimes, a progressive idealisation is carried out by matching with equivalent DEM simulations in periodic cells. These investigations justify a one-dimensional continuum modelling of the problem and provide key test data. Novel exact solutions are derived here for vertical flow using a linear version of the ‘ $\mu(I),\varPhi(I)$ -rheology’, for which the bulk friction $\mu$ and steady solid volume fraction $\varPhi$ depend on the inertial number I. Despite not capturing the full nonlinear complexities, the solutions match important aspects of the DEM flow fields and reveal simple scaling laws linking many quantities of interest. In particular, this study clearly demonstrates a linear relation between the chute width and the size of the shear zones at the walls. This finding contrasts with previous works on purely quasi-static flow, which instead predict a roughly constant shear zone width, a difference which implies that finite-size effects are minimal for the inertial flows studied here.

Non-invasive measurement of oil-water two-phase flow in vertical pipe using ultrasonic Doppler sensor and gamma ray densitometer

Oil–water two-phase flow experiments were conducted in a vertical pipe to study the liquid–liquid flow measurement using a non-invasive ultrasound Doppler flow sensor and a gamma-ray densitometer. Tap water and a dyed mineral oil are used as test the fluids. A novel Doppler effect strategy is used to estimate the mixture flow velocity in a vertical pipe based on flow velocity measured by the ultrasound sensor and the shear flow velocity profile model. Drift-flux flow model was used in conjunction phase fractions to predict the superficial velocities of oil and water. The results indicate that the proposed method estimated oil-continuous flow and water-continuous flow have average relative errors of 5.2% and 4.5%; and superficial phase flow velocities of oil and of water have average relative errors of 4.5% and 5.9% respectively. These results demonstrate the potential for using ultrasonic Doppler sensor combined with gamma densitometer for oil–water measurement.

Analysis of liquid-liquid (water and oil) two-phase flow in vertical pipes, applying artificial intelligence techniques

Due to the precision of its results, the use of artificial intelligence technology for predictive models for multiphase flow description currently has a considerable impact on industrial applications. This work compares the results obtained in an adaptive neuro-fuzzy inference system with the results obtained in an artificial neural network to predict the holdup of oil in vertical pipes with a water and oil mixture. We use pipe diameter, fluid surface velocity, and oil viscosity as input parameters. The research was conducted using 722 experimental data and found that the best model is a model generated by an artificial neural network with a hidden layer consisting of 12 neurons and using the Levenberg Marquardt training function and the TanSig activation function. The results showed a root mean square error of 0.000049, the coefficient R2 was 0.99932, and the average absolute percentage error was 0.19%. The predictive model can be used to improve transportation processes in the oil and gas sector.

Experiments and modelling of three-phase vertical pipe flow

A set of two- and three-phase experiments were conducted in a 50 m long 4″ vertical pipe using nitrogen, Exxsol D60 and water at 45 bara pressure. The results show that the liquid content and pressure drop are highly sensitive to the injected water cut. The proposed explanation for this surprising result is that the presence of liquid droplets constrains the gas bubble capacity of the liquid so that the concentration of small bubbles inside the liquid becomes smaller in three-phase flows than in two-phase flows.To test this hypothesis, a simple flow model was implemented using closure laws from the public literature, combined with the assumption that the concentration of gas bubbles is reduced by the presence of liquid droplets. The model shows that the observed three-phase effects can be reproduced very accurately using this assumption.

Direct numerical simulation of two-phase pipe flow: Influence of the domain length on the flow regime

We investigate the dynamics of a kerosene–water mixture in a vertical pipe flow by solving the Cahn–Hilliard–Navier–Stokes equations. We compute the linear stability of laminar core-annular flow in a vertical pipe and find that it is highly unstable. By performing direct numerical simulations initialized with a slightly perturbed core-annular flow, we show that the system transitions to turbulence and finally relaxes into a turbulent slug flow regime provided that the pipe is sufficiently long. This configuration presents mild turbulence and large scale three-dimensional recirculation patterns. Our work highlights the need for applying nonlinear-dynamics approaches and carefully selecting the domain length to investigate the patterns observed in two-phase pipe flows and demonstrates the capabilities of phase-field methods to reliably simulate flows under realistic experimental conditions.

Experimental Investigation of Oil-Water Two-Phase Flow in Horizontal, Inclined, and Vertical Large-Diameter Pipes: Determination of Flow Patterns, Holdup, and Pressure Drop

Summary Liquid-liquid phase flow in pipes merits further investigation as a challenging issue that has very rich physics and is faced in everyday applications. It is the main problem challenging the fluid flow mechanism in the oil and gas industry. The pressure gradient of liquid flow and flow pattern are still the topics of numerous research projects. In this paper, the emphasis is on further investigation to research the flow pattern, water holdup (HW), and pressure decrease for vertical, horizontal, and inclined flow directions of oil and water flows. Test section lines of 4.19-in. (106.426 mm) inner diameter (ID) and 5-m horizontal, 5-m inclined, and 5-m vertical test sections were serially connected. The experiments were conducted at 40°C using 2-cp viscosity oil and tap water, and oil density of 850 kg/m3, at the standard conditions. Fifty experiments were executed at 250 kPa at the multiphase flow test facility, with horizontal, upward (0.6° and 4°), downward (−0.6° and −4°) hilly terrain and vertical pipes. The oil and water superficial velocities were changed between 0.03 and 2 m/s. This evidence was obtained using video recordings; the flow patterns were observed, and the selection of each flow pattern was depicted for each condition. For horizontal and inclined flow, new flow patterns were documented (e.g., oil transfer in a line forms at the top of the pipeline, typically at high water rate, and water transfer at the lower part of the pipe at a high oil rate). The data were taken at each flow condition, resulting in new holdup and pressure drop. The results show that the flow rate and the pipe inclination angle have major impacts on the holdup and pressure drop performances. In the vertical flow, a clear peak was demonstrated by experiments after the superficial oil velocity reached a certain value. This peak is known as phase inversion point, where after this peak, the pressure starts declining as the superficial oil velocity increases. Also, slippage has been observed after varying inlet oil flow rates between the two phases. The experiments showed that with minor alteration in the inclination angle, the slippage was significantly changed. This study presented new experimental results (measured mainly at horizontal, inclined, and vertical flow conditions) of HW, flow pattern, and pressure drop. These findings are key evidence of the evolving oil-water and flowline estimate models.

A Two-Fluid Model for High-Viscosity Upward Annular Flow in Vertical Pipes

Proper selection and application of interfacial friction factor correlations has a significant impact on prediction of key flow characteristics in gas–liquid two-phase flows. In this study, experimental investigation of gas–liquid flow in a vertical pipeline with internal diameter of 0.060 m is presented. Air and oil (with viscosities ranging from 100–200 mPa s) were used as gas and liquid phases, respectively. Superficial velocities of air ranging from 22.37 to 59.06 m/s and oil ranging from 0.05 to 0.16 m/s were used as a test matrix during the experimental campaign. The influence of estimates obtained from nine interfacial friction factor models on the accuracy of predicting pressure gradient, film thickness and gas void fraction was investigated by utilising a two-fluid model. Results obtained indicate that at liquid viscosity of 100 mPa s, the interfacial friction factor correlation proposed by Belt et al. (2009) performed best for pressure gradient prediction while the Moeck (1970) correlation provided the best prediction of pressure gradient at the liquid viscosity of 200 mPa s. In general, these results indicate that the two-fluid model can accurately predict the flow characteristics for liquid viscosities used in this study when appropriate interfacial friction factor correlations are implemented.

Feasibility of harvesting rainwater for power generation

This paper discusses the possibility of using storage rainwater to produce electricity from high-rise residential buildings. Rainwater could be harnessed and funneled to drive a small dc generator. The tallest building on campus, RK Hostel, was selected for this study. It stands at a height of 20m and has a roof catchment area of 905 m2 which would accumulate 15,000 liters of rainwater. The amount of electric power (P) is determined by the vertical downspout pipe's pressure head (H) and flow rate (Q). The schematic model is developed in Matlab/Simulink and then simulated to see how much electricity it can generate. From the simulation results it is observed, a 17m vertical conduit pipe with a steady discharge rate of 7.8 lit/sec could produce about 600 watts of electricity.

Comparison of well-posedness criteria of two-fluid models for numerical simulation of gas-liquid two-phase flows in vertical pipes

The purpose of the present study is to compare the well-posedness criteria of the free-pressure two-fluid model, single-pressure two-fluid model, and two-pressure two-fluid model in a vertical pipe. Two-fluid models were solved using the conservative shock capturing method. A water faucet case is used to compare two-fluid models. The free pressure two-fluid model can accurately predict discontinuities in the solution field if the problem's initial condition satisfies the Kelvin Helmholtz instability conditions. The single-pressure two-fluid model can accurately predict the behavior of flows in which the two phases are poorly coupled. The two-pressure two-fluid model is an unconditionally well-posed one. If in the free-pressure two-fluid model and single-pressure two-fluid model, the range of velocity difference of two phases exceeds certain limits, the models will be ill-posed. The two-pressure two-fluid model produces more numerical diffusion than the free-pressure two-fluid and single-pressure two-fluid models in the solution field. High numerical diffusion of two-pressure two-fluid models leads to failure to better comply with the problem's analytical solution. Results show that a single-pressure model is a powerful model for numerical modeling of gas-liquid two-fluid-flows in the vertical pipe due to a broader range of well-posed than free-pressure models and less numerical diffusion than the two-pressure mode.

Numerical prediction of solid particle erosion under upward multiphase annular flow in vertical pipe bends

Solid particles entrained in the low liquid loading pipelines will cause pits or scratches on the pipe wall, and further lead to wall thinning or even leaks. Annular flow is a common flow pattern in pipeline. The particles in annular flow distribute in the liquid film and the gas core, and there are two existence forms for the solid particles in the gas core: wrapped in droplets and not be wrapped. In this paper, gas-particle slip was considered in a slip model in order to calculate the erosion of the particles wrapped in droplets in the gas core and a no-slip model was proposed to calculate the erosion of other particles in the gas core. The cushion effect of gas-liquid interface and the liquid film on the solid particles was equivalent to wall roughness. Finally, a simplified numerical simulation method considering the cushion effect and the gas-particle slip was developed to predict the erosion rate of vertical pipe bends. It is found that the predictions are in good agreement with the experimental data. The ratio of the solid particles wrapped in droplets to the total number of solid particles in the gas core is 0.626. Additionally, the relationship among liquid entrainment, erosion rate and liquid film thickness is investigated.

Pressure Loss Due to Hydraulic Transport of Large Solid Particles in Vertical Pipes Under Pulsating Flow Conditions

Abstract It is important to predict the pressure loss due to hydraulic transport of large solid particles for the design of subsea mining system. The mixture flow in the lifting pipe is expected to be unsteady in the actual mining system. The authors develop the one-dimensional mathematical model to predict the pressure loss of pulsating mixture flow in a static vertical pipe assuming that the flow in the pipe is fully developed. The experiment on hydraulic transport of solid particles was carried out to obtain the data for the investigation of the effects of flow fluctuation on pressure loss in a static vertical pipe. In the experiment, alumina beads and glass beads were used as solid particles, and the experimental parameters were mixture velocity, solid concentration, pulsating period, and pulsating amplitude. The proposed model was validated by a comparison with experimental data. Furthermore, we calculated the pressure losses due to hydraulic transports of polymetallic sulfide ores and manganese nodules using the proposed model. The calculation results showed that the fluctuating component in pulsating mixture flow should be considered for the design of lifting system and that the homogeneous mixture model could not be applied to the prediction of the pressure loss unless the mixture concentration is low and the pulsating period is short.

Numerical Prediction of Deposition in Two-Phase Flow in Vertical Pipes

Numerical Prediction of Deposition in Two-Phase Flow in Vertical Pipes

Benchmarking of computational fluid dynamic models for bubbly flows

Eulerian-Eulerian computational fluid dynamic (CFD) models allow the prediction of complex and large-scale industrial multiphase gas–liquid bubbly flows with a relatively limited computational load. However, the interfacial transfer processes are entirely modelled, with closure relations that often dictate the accuracy of the entire model. Numerous sets of closures have been developed, often optimized over few experimental data sets and achieving remarkable accuracy that, however, becomes difficult to replicate outside of the range of the selected data. This makes a reliable comparison of available model capabilities difficult and obstructs their further development. In this paper, the CFD models developed at the University of Leeds and the Helmholtz-Zentrum Dresden-Rossendorf are benchmarked against a large database of bubbly flows in vertical pipes. The research groups adopt a similar modelling strategy, aimed at identifying a single universal set of widely applicable closures. The main focus of the paper is interfacial momentum transfer, which essentially governs the void fraction distribution in the flow, and turbulence modelling closures. To focus on these aspects, the validation database is limited to experiments with a monodispersed bubble diameter distribution. Overall, the models prove to be reliable and robust and can be applied with confidence over the range of parameters tested. Areas are identified where further development is needed, such as the modelling of bubble-induced turbulence and the near-wall region, as well as the best features of both models to be combined in a future harmonized model. A benchmark is also established and is available for the testing of other models. Similar exercises are encouraged to support the confident application of multiphase CFD models, together with the definition of a set of experiments accepted community-wide for model benchmarking.

Experimental investigation of the characteristics of the transition from spherical cap bubble to slug flow in a vertical pipe

Reliable and accurate prediction of the transition from spherical cap bubble to slug flow is crucial not only to the operation of industrial facilities such as the crude oil pipelines, bubble column, and nuclear reactors but also for model development for computational fluid dynamics (CFD) studies. The present paper presents a review of the transition mechanics from spherical cap bubble flow to slug flow in vertical pipes. The bubble flow was split into sub-regions, bubbles and spherical cap bubbles and the mechanisms to classify them (i.e., bubble terminal velocity and cap bubble velocity) was analysed. For now, the literature review does not present some important previous works. This paper presents an original data set of gas–silicone oil in vertical pipes to support the new findings. The experimental two-phase data classifies the flow patterns using the probability density function (PDF) and shows the important flow variables such as average void fraction, pressure gradient, slug body void fraction, liquid slug, Taylor bubble and slug unit lengths, structural velocity and frequency obtained by electrical capacitance tomography (ECT) and a wire mesh sensor (WMS).

Frictional Pressure Drop and Liquid Holdup of Churn Flow in Vertical Pipes with Different Viscosities

Churn flow commonly exists in the pipe of heavy oil, and the characteristics of churn flow should be widely understood. In this paper, we carried out air and viscous oil two-phase flow experiments, and the diameter of the test section is 60 mm. The viscosity range of the oil was 100~480 mPa·s. Based on the measured liquid holdup and pressure drop data of churn flow, it can be concluded that, due to the existence of liquid film backflow, positive and negative frictional pressure drop can be found and the change of frictional pressure drop with the superficial gas velocity is related to superficial liquid velocity. With the increase of viscosity, the change rate of frictional pressure drop increases with the increase of the superficial gas velocity. Combining our previous work and the Taitel model, we proposed a new pressure drop model for viscous oil-air two-phase churn flow in vertical pipes. By comparing the predicted values of existing models with the measured pressure drop data, the proposed model has better performance in predicting the pressure drop.