Numerical modeling of wavy stratified two-phase flow in pipes

CFD Simulations of Abnormal Flow in Horizontal Pipes for Offshore Hydrocarbon Transport

Modeling the simultaneous flow of gas and liquid or two-phase gas-liquid flow in pipes is a key aspect in petroleum production. These models can enhance our ability to estimate fluid properties, predict pressure loss, liquid holdup, and flow pattern, and to see the effects of introducing concepts such as heat transfer to the system. Modeling two-phase flow phenomenon also allows visualization of the interaction of one property or parameter to another. The understanding of heat transfer in two-phase gas-liquid flow is important for economic and optimized operations.;This work focuses on the design of a PC-Based Software for modeling the effect of convective heat transfer on flow patterns in two-phase gas-liquid flow in pipes at all inclinations from -90° to +90° from horizontal, with the utilization of a temperature and pressure traverse along the length of the pipe. The implementation of this model in a computer program involves substantial calculations and correlations, some of which require iterative procedures.

A fully implicit EOS based compositional two-phase transient flow simulator in wellbores

The characteristics of two-phase flow in a vertical pipe are investigated to gain a better understanding of vibration excitation mechanisms. An analytical model for two-phase flow in a pipe was developed by Sim et al. (2005), based on a power law for the distributions of flow parameters across the pipe diameter, such as gas velocity, liquid velocity and void fraction. An experimental study was undertaken to verify the model. The unsteady momentum flux impinging on a ‘turning tee’ (or a ‘circular plate’) has been measured at the exit of the pipe, using a force sensor. From the measured data, especially for slug flow, the predominant frequency and the RMS value of the unsteady momentum flux have been evaluated. It is found that the analytical method, given by Sim et al. for slug flow, can be used to predict the momentum flux.

A study on the characteristics of upward air–water two-phase flow in a large diameter pipe

In order to clarify the microscopic flow structure, the ultrasonic Doppler method was applied to the measurement of two-phase bubbly flow in vertical pipe (i.d.50mm). Liquid flow structure might strongly be influenced by the characteristic of the injected bubbles, i.e. bubbles’ size and void fraction. In this study, a bubble generator was newly designed with the purpose to control the bubble size and void fraction, independent of liquid main-flow rate. The experiment was performed at z/d = 66 from the bubble generator. Liquid flow rates were of the Reynolds numbers ranging from Rem = 3700 to 6200. The gas flow rate was constant at JG = 0.00348(m/s) at the measurement position. By analyzing the bubbles’ picture, it was confirmed that bubble size distribution and average bubble size were almost constant if the liquid flow rate were changed. The ultrasonic Doppler method has the capability of measuring the instantaneous velocity profiles of both phases at the same time. By processing the data based on pattern recognition, the recorded data can be classified to several groups. Using this method, the authors have tried to measure the bubbly flow in rectangular channel. In the present study, the application of this method to bubbly flow in circular pipe was satisfactory to obtain the liquid velocity distribution in bubbly flow and surrounding bubbles. From these results, it was clarified that velocity profile in bubbly flow in circular pipe has a maximum value near the pipe wall. Furthermore, velocity profiles around the bubble are influenced by leading bubbles.

Godunov‐type algorithms are very attractive for the numerical solution of discontinuous flows. The reconstruction of the profile inside the cells is crucial to scheme performance. The non‐linear generalization of the discontinuous profile method (DPM) presented here for the modelling of two‐phase flow in pipes uses a discontinuous reconstruction in order to capture shocks more efficiently than schemes using continuous functions. The reconstructed profile is used to define the Riemann problem at cell interfaces by averaging of the components of the variable in the base of eigenvectors over their domain of dependence. Intercell fluxes are computed by solving the Riemann problem with an approximate‐state solver. The adapted treatment of boundary conditions is essential to ensure the quality of the computational results and a specific procedure using virtual cells at both extremities of the computational domain is required. Internal boundary conditions can be treated in the same way as external ones. Application of the DPM to test cases is shown to improve the quality of computational results significantly. Copyright © 2001 John Wiley & Sons, Ltd.

Modelling of stratified gas–liquid two-phase flow in horizontal circular pipes

Much debate surrounds the mechanisms responsible for the occurrence of blunt traumatic aortic rupture in car accidents, particularly on the role of the inertial body force experienced by the blood due to the abrupt deceleration. The isolated influence of such body forces acting on even simple fluid flows is a fundamental problem in fluid dynamics that has not been thoroughly investigated. This study numerically investigates the fundamental physical problem, where the pulsatile flow in a straight circular pipe is subjected to a transverse body force on a localized volume of fluid. The body force is applied as a brief rectangular impulse in three distinct cases, namely during the accelerating, peak, and decelerating phases of the pulsatile flow. A dimensionless number, termed the degree of influence of the body force (Ψ), is devised to quantify the relative strength of the body force over the flow inertia. The impact induces counter-rotating cross-stream vortices at the boundaries of the forced section accompanied by complex secondary flow structures. This secondary flow is found to develop slowest for an impact occurring during an accelerating flow and fastest during a decelerating flow. The peak skewness of the velocity field, however, occurred at successively later times for the three respective cases. After the impact, these secondary flows act to restore the unforced state and such dominant spatial structures are revealed by proper orthogonal decomposition of the velocity field. This work presents a new class of problems that requires further theoretical and experimental investigation.

The interfacial wave characteristics of stratified air-water two-phase flow in a horizontal pipe were experimentally investigated by using the flush-mounted constant electric current method (CECM) sensors. The experiments were conducted in a horizontal two-phase flow loop 9.5 m long (L) consisting of transparent acrylic pipe of 26 mm i.d. (D). To obtain the stratified flow pattern, the superficial gas and liquid velocities were set to 1.02 – 3.77 m/s and 0.016 – 0.92 m/s, respectively. Several interfacial wave patterns as described by several investigators were identified. The common parameters such as liquid hold-up, probability distribution function, wave velocity and wave frequency were investigated as the function of the liquid and gas flow rates. The interfacial curvature was calculated on the basis of the liquid hold-up data from the CECM sensors and the liquid film thickness data from the image processing technique in the previous work. As a result, it was found that the mean liquid hold-up decreases with the increase of the superficial gas velocity. In the same sub flow pattern, the wave velocity increases as the superficial gas velocity increases. On the other hand, in the two-dimensional wave region, the dominant frequency decreases with the increase of the superficial liquid velocity.

A simple friction pressure drop correlation for two-phase flow in pipes

This paper presents a simplified model for transient two-phase flow in pipes of any inclinations, for slow transients. Such simplified model facilitates its use for real-time monitoring and machine leaning implementations. An improved correlation for the drift flux parameters is adopted in the model, which enables the utilization of the model for simulating transient flow scenarios for any pipe inclination and extends its applicability to a wider range of conditions. From the formulation, an equation has also been proposed to quantitatively define the application of the concept of slow transient. This equation indicates if a case of interest can be classified as a slow transient, which consequently implies that the use of the proposed model would likely provide accurate results. The model has been validated with experimental and field data, and also compared to the state-of-the-art commercial simulator for transient two-phase flow in pipes. The results showed an agreement within the range of ±30% for the holdup predictions for 65% of the scenarios, and an agreement within the range of ±30% for the pressure predictions for 82% of the scenarios considered in the validation data set. The model performance evaluation with data from a well in the GOM showed a maximum error of 30% in terms of predicted bottomhole pressure and an average error of 9% for the simulation of two years of transient flows.

The horizontal stratified two-phase flow in the rectangular pipe whose width is smaller than the height is simulated by the one-component two-phase lattice Boltzmann method. The interfacial growth between two phases is measured for three cases with the different pipe width and the measured dimensionless number chasacterizing the two-phase flow is compared with the flow regime map proposed by Taitel and Dukler. It is found that the boundary separating the interfacial growth from the non-growth which is obtained by the simulations is larger than that in the flow regime map when the pipe width is narrower.

Correlation of heat transfer coefficient for two-component two-phase slug flow in a vertical pipe

The application potential of Capacitively Coupled Contactless Conductivity Detection (C <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> D) technique to the velocity measurement of gas-liquid two-phase flow in millimeter-scale pipe is investigated. Combining C <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> D technique and cross-correlation velocity measurement technique, a new velocity measurement method is proposed. The research work includes three parts. First, a three-electrode C <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> D sensor, which is suitable for the velocity measurement of gas-liquid two-phase flow in millimeter-scale pipe, is developed. Second, with the two independent conductivity signals of fluid obtained by the developed sensor, the velocity measurement of gas-liquid two-phase flow is implemented by the cross-correlation velocity measurement technique. Finally, velocity measurement experiments are carried out to verify the effectiveness of the proposed method. The research results indicate that the proposed velocity measurement method is effective and the developed sensor is successful. C <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> D technique may provide a useful approach for parameter measurement of gas-liquid two-phase flow in millimeter-scale pipe.