Numerical Investigation of Slug Flow in a Horizontal Pipe Using a Multi-Scale Two-Phase Approach to Incorporate Gas Entrainment Effects

2016 ◽  
Author(s):  
Stefan Wenzel ◽  
Marek Czapp ◽  
Thomas Sattelmayer
Keyword(s):  
Flow Regime ◽  
Slug Flow ◽  
Fluid Model ◽  
Interfacial Area ◽  
Experimental Investigations ◽  
Multiscale Approach ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Horizontal Pipes ◽  
Interface Capturing

Numerical as well as experimental investigations of the highly intermittent slug flow regime of a gas-liquid mixture in horizontal pipes are of particular interest for nuclear reactor safety in post loss-of-coolant accident (LOCA) situations. The strong variation of governing interfacial length scales, as they are characterizing the slug flow regime, pushes common numerical multi-phase approaches to their limits, since they are designed either for interface capturing or for modeling the sub-grid behavior of the dispersed mixture. In this work an enhanced hybrid two-phase flow solver is employed to investigate the global and local characteristics of adiabatic, horizontal slug flows in a water-air system. A dynamic switching algorithm for an interface capturing procedure is introduced to examine segregated and dispersed parts in the same flow domain. The inter-facial area transport equation (IATE) is used to detect dispersed flow regions as well as to determine variable bubble sizes and their distribution within the slug body. Experimental results of videometry measurements on a horizontal, 10 m long pipe with an inner diameter of 54 mm at atmospheric pressure and room temperature are compared with numerical results of the same geometry in terms of global characteristics such as slug frequency and onset position. Local properties, such as the interfacial area density in the slug body, are also examined. This study demonstrates the capability of a coupled multiscale approach based on the Euler-Euler two-fluid model (TFM) for the simulation of slug flow in horizontal pipes with a high amount of entrainment.

Numerical Simulation of the Transient Development of Slug Flow in Horizontal Pipes

2016 ◽  
Vol 819 ◽  
pp. 300-304 ◽  
Author(s):  
Zahid Ibrahim Al-Hashimy ◽  
Hussain H. Al-Kayiem ◽  
Mohammad Shakir Nasif ◽  
Abdalellah. O. Mohmmed
Keyword(s):  
Flow Regime ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Piping System ◽  
Phase Flow ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Horizontal Pipes ◽  
Flow Phenomena ◽  
Multi Phase Flow

Slug flow regime in two and multi-phase flow in pipes is a complicated flow phenomena representing challenge in the design of the piping system. In the present work, water/air two phase flow was modeled and simulated as 3 dimensional, transient, and incompressible flow using Volume of Fluid technique in STAR-CCM+ software. The simulation was conducted to predict and evaluate the air-water slug flow in a horizontal pipe with 0.16 m diameter and 7 m long. The superficial velocities for both phases were extracted from Baker chart slug zone. The results were validated against experimental bench marking referenced in Baker chart and the proposed VOF technique shows a good capability in simulating the development of the slug flow regime. This model could be utilized for simulation of various two phase flow regimes.

Validation of 2D CFD for Two-Phase Transient Flow in a Channel and Comparison With 1D Model

2012 ◽  
Author(s):  
Stamatis Kalogerakos ◽  
Mustapha Gourma ◽  
Chris Thompson
Keyword(s):  
Flow Regime ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Fluid Model ◽  
Volume Of Fluid ◽  
Inviscid Limit ◽  
Phase Flow ◽  
Two Phase ◽  
Vof Model ◽  
Two Fluid

Severe limitations of the use of three-dimensional computational fluid dynamics codes (CFD) arise when trying to simulate multiphase flow in long pipes due to time constraints. 1D codes for two-phase flow, based on two-fluid models, are fast but are known to be accurate only when the velocities are within the Kelvin-Helmholtz inviscid limit [1]. An alternative is to carry out a two-dimensional CFD simulation of a channel based on the Volume of Fluid (VOF) model. 2D CFD has a wider applicability range compared to 1D, it does not have the issue of ill-posedness and it also has better turbulence models built in. Again compared to 1D the 2D VOF model has a better interface description and wall treatment. In this paper a novel method is introduced that allows swift simulations of pipeline two-phase flow in the stratified and slug flow regime, by approximating the pipe as a channel and with a methodology that solves the problem of the interfacial velocity differences, inherent in the volume of fluid model. An initial validation using the wave growth problem has already been carried out [2]. Here a set consisting of 92 experimental cases in the slug flow regime has been simulated with 2D CFD, and the simulation results showed a good agreement with experimental results. Discussions in the paper include also the question of the range of applicability for 2D CFD, and the advantages and disadvantages compared to 3D CFD and also to 1D code based on the two-fluid model. Shear stresses are then extracted from the 2D CFD simulations and used to recalibrate the friction factors [3] used in the 1D code.

Water Hammer in Horizontal Water-Steam Counter-Current Flow

2006 ◽  
Author(s):  
Janez Gale
Keyword(s):  
Flow Regime ◽  
Current Flow ◽  
Fluid Model ◽  
Water Hammer ◽  
Test Facility ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Water Steam ◽  
Counter Current Flow ◽  
Counter Current

A six-equation, one-dimensional, two-fluid model of the two-phase flow, incorporated into the recently developed computer code WAHA, was used to model water hammer transient initiated with liquid-vapor counter-current flow in the horizontal pipe. The applied flow regimes and closure relations of the WAHA code for the inter-phase exchange of mass, momentum and energy are described and discussed. Although the WAHA code flow regime maps turned out to be sufficient and accurate for simulations of the column separation type of the fast transients, the current analysis pointed out the need to introduce some limiting values for dispersed flow regime correlations in order to successfully simulate water hammer initiated by condensation-induced counter-current flow. The WAHA code with modified relaxation source terms was then successfully utilized for simulations of the experiments performed at the Hungarian PMK-2 test facility.

On Instabilities in Horizontal Two-Phase Flow

1994 ◽  
Vol 59 (12) ◽  
pp. 2595-2603
Author(s):  
Lothar Ebner ◽  
Marie Fialová
Keyword(s):  
Differential Equation ◽  
Flow Regime ◽  
Slug Flow ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Annular Flows ◽  
Flow Regime Maps

Two regions of instabilities in horizontal two-phase flow were detected. The first was found in the transition from slug to annular flow, the second between stratified and slug flow. The existence of oscillations between the slug and annular flows can explain the differences in the limitation of the slug flow in flow regime maps proposed by different authors. Coexistence of these two regimes is similar to bistable behaviour of some differential equation solutions.

scholarly journals Research on the Dynamic Responses of Simply Supported Horizontal Pipes Conveying Gas-Liquid Two-Phase Slug Flow

Processes ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 83
Author(s):  
Gang Liu ◽  
Zongrui Hao ◽  
Yueshe Wang ◽  
Wanlong Ren
Keyword(s):  
Slug Flow ◽  
Peak Frequency ◽  
Dynamic Responses ◽  
Piping System ◽  
Transverse Displacement ◽  
Vibration Acceleration ◽  
Two Phase ◽  
Horizontal Pipes ◽  
Simply Supported ◽  
Superficial Gas Velocity

The dynamic responses of simply supported horizontal pipes conveying gas-liquid two-phase slug flow are explored. The intermittent characteristics of slug flow parameters are mainly considered to analyze the dynamic model of the piping system. The results show that the variations of the midpoint transverse displacement could vary from periodic-like motion to a kind of motion whose amplitude increases as time goes on if increasing the superficial gas velocity. Meanwhile, the dynamic responses have certain relations with the vibration acceleration. By analyzing the parameters in the power spectrum densities of vibration acceleration such as the number of predominant frequencies and the amplitude of each peak frequency, the dynamic behaviors of the piping system like periodicity could be calculated expediently.

Initiation and Statistical Evolution of Horizontal Slug Flow With a Two-Fluid Model

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
A. O. Nieckele ◽  
J. N. E. Carneiro ◽  
R. C. Chucuya ◽  
J. H. P. Azevedo
Keyword(s):  
Experimental Data ◽  
Slug Flow ◽  
Fluid Model ◽  
Subsequent Development ◽  
Complex Flow ◽  
Horizontal Pipes ◽  
Dimensional Version ◽  
Two Fluid Model ◽  
Log Normal ◽  
Two Fluid

In the present work, the onset and subsequent development of slug flow in horizontal pipes is investigated by solving the transient one-dimensional version of the two-fluid model in a high resolution mesh using a finite volume technique. The methodology (named slug-capturing) was proposed before in the literature and the present work represents a confirmation of its applicability in predicting this very complex flow regime. Further, different configurations are analyzed here and comparisons are performed against different sets of experimental data. Predictions for mean slug variables were in good agreement with experimental data. Additionally, focus is given to the statistical properties of slug flows such as shapes of probability density functions of slug lengths (which were represented by gamma and log-normal distributions) as well as the evolution of the first statistical moments, which were shown to be well reproduced by the methodology.

Experimental Characterization of Slug Flow Velocity Distribution in Two Phase Pipe Flow

2009 ◽  
Author(s):  
Afshin Goharzadeh ◽  
Peter Rodgers
Keyword(s):  
Velocity Distribution ◽  
Slug Flow ◽  
Two Phase ◽  
Significant Drop ◽  
Horizontal Pipe ◽  
Measured Velocity ◽  
Air Bubble ◽  
Velocity Magnitude ◽  
Index Matching ◽  
Refractive Index Matching

This paper presents an experimental study of gas-liquid slug flow inside a horizontal pipe. The influence of air bubble passage on liquid flow is characterized using Particle Image Velocimetry (PIV) combined with Refractive Index Matching (RIM) and fluorescent tracers. A physical insight into the velocity distribution within slug flow is presented. It was observed that the slug flow significantly influences the velocity profile in the liquid film. Measured velocity distributions also revealed a significant drop in the velocity magnitude immediately upstream of the slug nose. These findings aim to aid an understanding of the mechanism of solid transportation in slug flows.

A Physically Based, One-Dimensional Two-Fluid Model for Direct Contact Condensation of Steam Jets Submerged in Subcooled Water

2015 ◽  
Vol 1 (2) ◽  
Author(s):  
David Heinze ◽  
Thomas Schulenberg ◽  
Lars Behnke
Keyword(s):  
Direct Contact ◽  
Two Phase Flow ◽  
Fluid Model ◽  
Interfacial Area ◽  
Phase Flow ◽  
Two Phase ◽  
One Dimensional ◽  
Two Fluid Model ◽  
Contact Condensation ◽  
Two Fluid

A simulation model for the direct contact condensation of steam in subcooled water is presented that allows determination of major parameters of the process, such as the jet penetration length. Entrainment of water by the steam jet is modeled based on the Kelvin–Helmholtz and Rayleigh–Taylor instability theories. Primary atomization due to acceleration of interfacial waves and secondary atomization due to aerodynamic forces account for the initial size of entrained droplets. The resulting steam-water two-phase flow is simulated based on a one-dimensional two-fluid model. An interfacial area transport equation is used to track changes of the interfacial area density due to droplet entrainment and steam condensation. Interfacial heat and mass transfer rates during condensation are calculated using the two-resistance model. The resulting two-phase flow equations constitute a system of ordinary differential equations, which is solved by means of the explicit Runge–Kutta–Fehlberg algorithm. The simulation results are in good qualitative agreement with published experimental data over a wide range of pool temperatures and mass flow rates.

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