Flow In Annular Pipe Research Articles

Investigating Reynolds number effects in turbulent concentric coaxial pipe flow using stochastic one‐dimensional turbulence modeling

AbstractThe present study numerically investigates turbulent momentum transfer in concentric coaxial (annular) pipe flow with small radius ratios . To model the flow, a stochastic one‐dimensional turbulence (ODT) model formulated for cylindrical geometry is used that provides full‐scale resolution along a representative radial coordinate. The present investigation extends the model validation by Tsai et al. (PAMM, 22:e202200272, 2023), to radius ratios smaller than 0.1 and addresses boundary layers with strong spanwise curvature effects. The focus is on the assessment and analysis of statistical flow features in the vicinity of the inner cylinder wall, particularly in cases with small radius ratios. Following Boersma & Breugem (Flow Turbul. Combust., 86:113–127, 2011), classical boundary‐layer and mixing‐length theory is utilized to analyze the model predictions. The results demonstrate that the ODT model captures leading‐order curvature and mixing‐length effects by its physics‐compatible construction. Utilizing the model for extrapolation to high Reynolds numbers inaccessible to conventional high‐fidelity numerical approaches shows that curvature effects persist and nonlocally affect the entire boundary layer. The model results provide support for a spanwise‐curvature‐modified wall function.

An artificial neural network model for the prediction of entrained droplet fraction in annular gas-liquid two-phase flow in vertical pipes

An artificial neural network model for the prediction of entrained droplet fraction in annular gas-liquid two-phase flow in vertical pipes

Modeling simultaneous momentum and passive scalar transfer in turbulent annular Poiseuille flow

AbstractSimultaneous momentum and passive scalar transfer in weakly heated pressure‐driven turbulent concentric annular pipe flow is numerically investigated using the cylindrical formulation of the stochastic one‐dimensional turbulence (ODT) model, which is utilized here as standalone tool. In the present study, we focus on the model calibration for heated annular pipes based on recent reference direct numerical simulations (DNS) from Bagheri and Wang (Int. J. Heat Fluid Flow 86, 108725, 2020; Phys. Fluids 33, 055131, 2021). It is shown that the model is able to individually capture scalar and momentum transfer, but not both equally well at the same time. We attribute this to less dissimilar scalar and momentum transport in the model at the low Reynolds number investigated. It is argued that the model prefers a fully developed turbulent state due to its construction. Nevertheless, it is demonstrated that ODT is able to reasonably capture the radial inner‐outer asymmetry of the scalar and momentum boundary layers which yields better predictive capabilities than wall‐function‐based approaches.

CFD-DEM investigation of gas–solid swirling flow in an industrial-scale annular pipe

Swirling gas-particle flow has been prevalently utilized in many industrial applications due to the obvious advantages of high particle dispersity, small pressure drop and low power consumption. In this work, numerical simulation of the swirling gas–solid two-phase flow in the three-dimensional industrial-scale annular pipe installed with a helical swirler is carried out via computational fluid dynamics coupled with discrete element method. The mixing characteristics of two-axial jets together with the particle-scale information of solid phase are fully investigated. The results show that the high Reynolds number of gas phase is observed above the swirl generator, while high turbulent Reynolds number of gas phase mainly appears in the core region of the mixing zone. The existence of the swirler vorticity in the high-velocity jet increases the strain rate of gas phase. The cross-section distribution of the particles always follows the normal distribution pattern, and the velocity components of the outermost particle are dramatically higher than those in the core region. Due to the entrainment effect of swirling gas flow, the velocity and dispersion width of the particles increase when moving downward. Swirling flow of gas phase obviously impacts the particle velocity and entrained number within the height of the z/H = 0.2 to 0.1 but only affects the particle entrained number in the range of z/H = 0.1 to 0.

Particle-scale modeling study of coaxial jets of gas-solid swirling flow in an industrial-scale annular pipe via CFD-DEM

In this work, the gas-solid swirling flow characteristics of coaxial jets in an industrial-scale annular pipe with a helical swirler is numerically simulated via the CFD-DEM. After validating the numerical model, the general flow pattern of coaxial jets, and gas-particle mixing behavior together with the particle-scale information are discussed. The effect of the geometry parameters of the swirler is studied and analyzed in terms of particle azimuthal velocity and particle Reynolds number. The results demonstrate that the presence of the swirler enhances both the turbulent disturbance and gas vorticity. Increasing vane angle and diameter of swirler is beneficial for the particle dispersion. The particle velocity slightly reduces with decreasing the height in the region 0.6 m < H < 0.7 m but dramatically increases with decreasing the height in the region of height H < 0.6 m. The entrainment of particles by the swirling flow increases the distribution width and azimuthal velocity of particles with decreasing the height.

Specialist system in flow pattern identification using artificial neural Networks

In this work, an application of artificial intelligence in the oils &amp; gas industry is developed to identify flow patterns in horizontal and vertical pipes of two-phase flow of oil and water, normalizing the word information and converting it to numerical values through the development of an artificial neural network, whose input layer is composed of the surface velocities of each fluid, the velocity of the mixture, the volumetric fraction of the substances, diameter and the inclination of pipelines and the oil viscosity. The Artificial Neural Networks (ANN) has two hidden layers composed of 45 neurons. The database with which the model was trained, validated, and tested has 6993 rows of information corresponding to the inputs of the intelligent system and particular-ized for annular flow in horizontal pipes and DO/W in vertical pipelines. Notice that the information was obtained after re-engineering the information presented by 12 and 18 authors for horizontal and vertical piping, respectively. Finally, the mean square error obtained by the model was around 1.38%, with a maximum coefficient of determination of 0.79.

Two-Phase Annular Flow in Vertical Pipes: A Critical Review of Current Research Techniques and Progress

Two-phase annular flow in vertical pipes is one of the most common and important flow regimes in fluid mechanics, particularly in the field of building drainage systems where discharges to the vertical pipe are random and the flow is unsteady. With the development of experimental techniques and analytical methods, the understanding of the fundamental mechanism of the annular two-phase flow has been significantly advanced, such as liquid film development, evolution of the disturbance wave, and droplet entrainment mechanism. Despite the hundreds of papers published so far, the mechanism of annular flow remains incompletely understood. Therefore, this paper summarizes the research on two-phase annular flow in vertical pipes mainly in the last two decades. The review is mainly divided into two parts, i.e., the investigation methodologies and the advancement of knowledge. Different experimental techniques and numerical simulations are compared to highlight their advantages and challenges. Advanced underpinning physics of the mechanism is summarized in several groups including the wavy liquid film, droplet behaviour, entrainment and void fraction. Challenges and recommendations are summarized based on the literature cited in this review.

Three-dimensional intermittent structure and flow map for concentric/eccentric annular Poiseuille flow

We conducted three-dimensional flow visualization of concentric/eccentric annular pipe flows in a transitional Reynolds-number regime with a single camera. One of our goals is to provide the first experimental evidence of helically-shaped intermittent turbulent structures in the concentric annular pipe flow, which has been reported only by a numerical simulation [Ishida et al., J. Fluid Mech. 794, R2 (2016)]. Another aim is to reveal the effect of the eccentricity on the intermittent structures that the gap instability caused in an eccentric annular pipe flow. A parametric study was executed for the radius ratios from 0.14 to 0.43 and the eccentricities from 0 to 0.8 (the ratio of the axes distance to a half of the hydraulic diameter). For the concentric cases with high radius ratios of 0.29 and 0.43, we confirmed the helical turbulence and helical puff. With intermediate eccentricities, such helical structures did not appear, instead weak turbulence and staggered vortices survived at much lower Reynolds numbers, i.e., the relaminarization was delayed because of the gap instability. For the highest eccentricity of 0.8, a transitional structure like a puff in a pipe flow without the inner pipe was observed due to the absence of the cross flow through the narrow gap between the cylinders.

Direct Numerical Simulation of Drag Reduction and Heat Transfer Enhancement by Wall Oscillation in Turbulent Concentric Annular Pipe Flow

In fluid engineering, the reduction of the skin-friction drag and the enhancement of the heat transfer are of importance in turbulent flows. In the present study, we made direct numerical simulations of the concentric annular turbulent pipe flow controlled by the wall oscillation control technique for the skin-friction reduction and heat transfer enhancement. The concentric annular pipe is widely used, and we expected to obtain the control effect by using the different radius of the inner and outer cylinders. Two types of control methods are shown: the wall oscillation technique and the traveling wave-like wall oscillation. In the wall oscillation, the friction drag decreases at all the frequencies, and the similarity between momentum and heat transport is maintained. In the traveling wave, the wave speed significantly affects the friction drag and the heat transfer. In some cases, the dissimilarity between momentum and heat transport is also confirmed.

A new model for viscous oil-water eccentric core annular flow in horizontal pipes

Eccentric core-annular flow is encountered in water-lubricated transport of highly viscous oil in horizontal pipes. The core eccentricity results from the tendency of the phases to stratify due to a buoyant force that results from their different densities, whereby a shape of a circular core may not be maintained. To model such a flow configuration, a new three-zone model is proposed based on the Two-Fluid approach. The model's performance was examined by comparing its predictions with a large data set of pressure gradient and water holdup values obtained under different experimental conditions. It is shown that the proposed model enables better agreement with the data compared to other models available in the literature. Thus, the proposed approach appears to be a useful framework for modeling viscous oil-water eccentric core-annular flows. It can also be applied for other types of Newtonian/non-Newtonian or non-Newtonian/non-Newtonian liquid-liquid core flows encountered in industrial applications.

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.

Direct numerical simulation of turbulent heat transfer in concentric annular pipe flows

The effect of radius ratio on turbulent convective heat transfer within a concentric annular pipe has been studied using direct numerical simulation. Four radius ratios (Ri/Ro = 0.1–0.7) have been compared at a fixed Reynolds number, where Ri and Ro denote the radii of the inner and outer pipes, respectively. The statistical moments of the temperature field, budget balances of the temperature variance and turbulent heat fluxes, and turbulence structures that dominate the heat transfer process have been thoroughly studied in both physical and spectral spaces. It is observed that the radius ratio has a significant impact on the Nusselt numbers and skin friction coefficients of the inner and outer cylinder walls, and on the interaction of thermal boundary layers developed over these two curved walls. Owing to the curvature difference between the two cylinder surfaces, the thermal boundary layer developed over the outer cylinder wall is thicker than that over the inner cylinder wall. Also, turbulent heat transfer is more intense on the outer cylinder side than on the inner cylinder side. As the radius ratio decreases, the difference in turbulence statistics between the inner and outer cylinder sides becomes increasingly pronounced. It is also observed that both axial and azimuthal characteristic length scales of the most energetic turbulent thermal structures are larger on the inner cylinder side than on the outer cylinder side.

Evaluation of Velocity Impact on Sand Particles in Two-Phase Annular Flow in Horizontal Pipes

Experimental investigations on sand particles in annular flow in horizontal pipes were presented. The aim is to enhance the knowledge related to sand transportation in the oil and gas industry. More so, to add values in facilitating the optimum design of oil and gas production systems where annular flow is often encountered. The experimental investigations were conducted using a closed-loop consisting of a horizontal pipe with an internal diameter of 2-inch (0.0504m). The experimental investigations covered both: water/sand flow and water/air/sand annular flow. The water/sand flow experiments were carried out to establish sand transport regime in liquid such as sand saltation, sand streak, and sand suspension. While, water/air/sand annular flow experiments revealed that the only the only sand transport regime in annular flow are saltation and suspension. Sand concentration profile in the annular flows were also estimated by using the sampling method. It was found that the bigger the sand particle size (500microns) leads to higher concentration of sand being transported at the bottom of the pipe because of gravity effect, while the smaller the sand particle size (212microns), leads to the higher sand concentration. Also, the sand concentration increased at the gas core as the superficial gas velocity increases.

Experimental and CFD simulation of slurry flow in the annular flow path using two-fluid model

The current study is allocated to experimental evaluation of the multiphase flow of fine solid particles (FSPs) as well as comprehensive numerical study in an annular space under static, laminar, and turbulent flow conditions with consideration of the inner pipe eccentricity and rotation. The experimental investigation was carried out using an annular pipe flow loop. The numerical modeling and simulation of the multiphase flow in the annular space have been performed using the Euler-Euler approach. The unsteady-state multiphase model based on the kinetic theory of granular flow (KTGF) is developed to investigate the particulate flow characteristics in the annular space. Moreover, Standard and Realizable k-ε turbulence models used to predict turbulence in this study. The Realizable Per-Phase turbulence model with new corrected coefficients (C2=4.2,C3=1.3,CT=0.0131,σk=1,σε=1.2) is calibrated to predict the pressure drop along the annular pipe for solid-liquid multiphase flow. Comparison between numerical and experimental analyses showed that under both flowing and static conditions, the simulation results are in good agreement with experimental data. Based on the error estimation model, the CFD model's accuracy for pressure drop and FSPs concentration prediction is 99% and 95%, respectively. The trends of the variation in particle concentration along the annular pipe were investigated for different flow velocities (0.05–2.5 m/s) and different inner pipe rotations of 500, 1000, and 1500 rpm. The results also showed that the higher particle settling occurred at the critical inclination angles of 45–60°.

Large‐Eddy Simulation of Oil‐Water Annular Flow in Eccentric Vertical Pipes

AbstractOne of the difficulties related to oil exploration is transporting heavy oil since its high viscosity causes high‐pressure drop and energy consumption. In order to save energy, the core annular flow (CAF) can be applied where a two‐phase annular flow occurs, with peripheral water flowing offering a reduction in energy expenditure. The multiphase flow was studied experimentally in a simple purpose‐built unit. To theoretically handle the CAF, computational fluid dynamics simulations were done with the commercial package Ansys Fluent. The flow was considered turbulent, isothermal, incompressible, and 3D, and both stationary and transient cases were evaluated. The volume‐of‐fluid model was adopted for the multiphase system, and water/oil interface and turbulence phenomena were well predicted.

Effects of radius ratio on turbulent concentric annular pipe flow and structures

The effects of radius ratio on fully-developed turbulent concentric annular pipe flow and structures are investigated using direct numerical simulations (DNS). In order to study the radius ratio effects on the flow, four radius ratios of a concentric annular pipe (for Ri∕Ro=0.1–0.7) are compared at a fixed Reynolds number. Here, Ri and Ro are the radii of the inner and outer pipes, respectively. It is observed that the radius ratio influences the interaction of two boundary layers developed over the inner and outer cylinder surfaces, and has a significant impact on the turbulent flow structures and dynamics. The characteristics of the flow field are investigated in both physical and spectral spaces, which include the analyses of the first- and second-order statistical moments, budget balance of the transport equation of Reynolds shear stress, two-point correlation coefficients, and premultiplied spectra of velocity and vorticity fluctuations.

Predication of wall shear stress of vertical upward co-current adiabatic air-water annular flow in pipes

Annular flow has been widely applied to industrials such as oil extraction, refrigerators, nuclear reactors and so on. Wall shear stress is one of the most important parameters for studying two-phase annular flow. When calculating wall shear stress from interfacial shear stress, the relationship between the wall shear stress and the interfacial shear stress is complicated and needs some parameters such as film thickness which requires high-precision measurement technique to acquire accurately. Besides, some wall shear stress correlations developed for annular flow are applicable to flow conditions at atmospheric pressure only. Because of these reasons, four databases for vertical upward co-current adiabatic air-water two-phase annular flow have been collected with wide range of flow conditions and different pressure conditions. Using these data, a simplified model between wall shear stress and interfacial shear stress is proposed. The new model is derived from the force balance analysis of the liquid film and gas core. As void fraction of annular flow is close to 1, the relationship between wall shear stress and interfacial shear stress can be simplified to be linearly. Based on this model and existing interfacial shear stress correlations, the wall shear stress can be calculated directly from flow conditions and fluid properties that can be readily obtained from experiments. Also, a new wall shear stress correlation calculated from wave velocities has been suggested. It is developed from frictional pressure drop correlation. Correlations for two-phase multiplier and wave velocity as well as pure empirical correlations also have been compared with existing databases. From data comparison, the newly proposed correlations in this study agree well with experimental data and other correlations with good prediction accuracy have been pointed out.

X-ray measurements of thin liquid films in gas–liquid pipe flow

This paper presents a method for reconstructing the thickness profile of the thin liquid film being present in steady, fully developed gas–liquid annular pipe flow, taking advantage of nonintrusive X-ray measurements. Experiments have been performed with low liquid loading, annular flows, in a near horizontal pipe system (inclination +2.5°), using a high-density gas (SF6) and Exxsol D60 oil. Special care was taken to ensure the flows were fully developed, and statistically steady. The superficial gas velocity was maintained at a constant value of 10 m/s, while the superficial liquid velocity was varied between 0.5 mm/s and 42 mm/s. The X-ray measurements were supplemented by gamma ray densitometer data and isokinetic data. An explicit mathematical method is presented, whereby the shape and thickness of very thin liquid films can be reconstructed if X-ray images of the flow have been obtained from two independent directions: one with a vertical view of the pipe, and another with a horizontal side view. The method can be straightforwardly applied to cases where the film volume dominates the total volume of droplets suspended in the gas phase. This condition is generally satisfied for the experiments presented in this paper, as verified by isokinetic measurements.Mean liquid hold-up values determined by gamma densitometer are in reasonable agreement with the X-ray results. It is found that the mean film thickness at any position on the pipe wall increases with the superficial liquid velocity. While the film thickness is maximal at the pipe bottom in virtually all experimental cases, its profile exhibits multiple local maxima and minima, with the smallest thickness apparently 20°–30° away from at the pipe top. The presented film reconstruction method is highly sensitive; even at extremely low liquid levels, with a superficial liquid velocity less than 0.01% of the mixture velocity, the film and its thickness profile are clearly detected. An analytical fit for the film profile as a function of perimeter angle and superficial liquid velocity is given. The fit captures the main features of the profile as derived from X-ray measurements, for thin films with maximum thickness less than 5% of the pipe diameter.

Nano-particle deposition in laminar annular pipe flows

The transport and deposition of nano-particles in annular pipe flows under laminar conditions were studied. The Lagrangian particle tracking method was used to simulate the Brownian diffusion of ultrafine solid particles in a three-dimensional domain. The effects of nano-particle size, flow rate, inner and outer pipe diameters, pipe length, and temperature were studied. The computational models for the deposition of nano-particles in tubular, as well as annular pipe flows, were validated. Furthermore, using the CFD simulations and the Lagrangian particle tracking results, a new correlation for evaluating the deposition fraction of nano-particles in annular pipe flows was developed. The presented results could provide guidelines for evaluating nano-particle transport and deposition in annular pipes.

On the rise characteristics of Taylor bubbles in annular piping

A three-dimensional phase-field lattice Boltzmann method has been applied to investigate the rise of Taylor bubbles within annular pipes. The approach couples the conservative phase-field model with a velocity-based lattice Boltzmann scheme. The implementation uses 27 discrete velocities to resolve both the interfacial dynamics and the hydrodynamics. To assist numerical stability for the high-density ratio, two-phase flows a weighted multiple-relaxation-time collision operator is employed. This paper makes contributions in three areas. First, the model is employed to capture the behaviour of Taylor bubbles in five combinations of vertical annular pipes, with results compared to experimental findings from the literature for air-water flows. From this, shortcomings were identified in the ability of existing correlations to accurately predict rise velocities for bubbles in various liquids. Second, the effect of pipe inclination on the rise behaviour of the bubbles was investigated. From the findings, a preliminary correlation describing the rise velocity was proposed. The first two components of the study were conducted with the Taylor bubble rising in stagnant fluid. The final component of this study imposed liquid flow in a concentric annular pipe to determine the impact of this on the bubble’s dynamics. The liquid velocity was defined through a Reynolds number based on the average inlet velocity up to an absolute value of 10. The viscosity was varied to examine Morton numbers from 2.56e-3 to 6.55e-5. To this end both co- and counter-current flow was analysed and a distribution parameter proposed to capture the liquid-gas interaction. To extend this work, future investigations will look to extend the parameter range assessed to ensure the universality of the correlations identified.