Modeling of Slug Dissipation and Generation in Gas-Liquid Hilly-Terrain Pipe Flow

2003 ◽  
Vol 125 (3) ◽  
pp. 161-168 ◽  
Author(s):  
Hong-Quan Zhang ◽  
Eissa M. Al-Safran ◽  
Subash S. Jayawardena ◽  
Clifford L. Redus ◽  
Cem Sarica ◽  
...  
Keyword(s):  
Pipe Flow ◽  
Slug Flow ◽  
Control Volume ◽  
Unit Length ◽  
Mineral Oil ◽  
Hilly Terrain ◽  
Two Phase ◽  
Oil Flow ◽  
Flow Experiences ◽  
Good Agreement

Hilly-terrain pipelines consist of interconnected horizontal, uphill and downhill sections. Slug flow experiences a transition from one state to another as the pipe inclination angle changes. Normally, slugs dissipate if the upward inclination becomes smaller or the downward inclination becomes larger, and slug generation occurs vice versa. Appropriate prediction of the slug characteristics is crucial for the design of pipeline and downstream facilities. In this study, slug dissipation and generation in a valley pipeline configuration (horizontal-downhill-uphill-horizontal) were modeled by use of the method proposed by Zhang et al. The method was developed from the unsteady continuity and momentum equations for two-phase slug flow by considering the entire film zone as the control volume. Computed results are compared with experimental measurements at different air-mineral oil flow rate combinations. Good agreement is observed for the change of slug body length to slug unit length ratio.

Modeling of Slug Dissipation and Generation in a Hilly-Terrain Pipeline

2001 ◽  
Author(s):  
Hong-Quan Zhang ◽  
Eissa M. Al-Safran ◽  
Subash S. Jayawardena ◽  
Clifford L. Redus ◽  
James P. Brill
Keyword(s):  
Flow Rate ◽  
Slug Flow ◽  
Liquid Flow Rate ◽  
Control Volume ◽  
Unit Length ◽  
Experimental Measurements ◽  
Hilly Terrain ◽  
Gas Liquid Flow ◽  
Flow Experiences ◽  
Good Agreement

Abstract Hilly-terrain pipelines consist of interconnected horizontal, uphill and downhill sections. Slug flow experiences a transition from one state to another as the pipe inclination angle changes. Normally, slugs dissipate if the upward inclination becomes smaller or the downward inclination becomes larger, and slug generation occurs vice versa. Appropriate prediction of the slug characteristics is crucial for the design of pipeline and downstream facilities. In this study, slug dissipation and generation in a valley pipeline configuration (horizontal-downhill-uphill-horizontal) were modeled by use of the method proposed by Zhang et al. [1]. The method was developed from the unsteady continuity and momentum equations for slug flow by considering the entire film zone as the control volume. Computed results are compared with experimental measurements at different gas-liquid flow rate combinations. Good agreement is observed for the change of slug body length to slug unit length ratio.

Unified Model for Gas-Liquid Pipe Flow Via Slug Dynamics: Part 1 — Model Development

2002 ◽  
Author(s):  
Hong-Quan Zhang ◽  
Qian Wang ◽  
Cem Sarica ◽  
James P. Brill
Keyword(s):  
Flow Pattern ◽  
Pipe Flow ◽  
Slug Flow ◽  
Control Volume ◽  
Model Development ◽  
Flow Patterns ◽  
Hydrodynamic Characteristics ◽  
Momentum Exchange ◽  
Two Phase ◽  
Inclination Angles

A unified hydrodynamic model is developed for predictions of flow pattern transitions, pressure gradient, liquid holdup and slug characteristics in gas-liquid pipe flow at different inclination angles from −90 to 90 deg. The model is based on the dynamics of slug flow, which shares transition boundaries with all the other flow patterns. By use of the entire film zone as the control volume, the momentum exchange between the slug body and the film zone is introduced into the momentum equations for slug flow. The equations of slug flow are used not only to calculate the slug characteristics, but also to predict transitions from slug flow to other flow patterns. Significant effort has been made to eliminate discontinuities among the closure relationships through careful selection and generalization. The flow pattern classification is also simplified according to the hydrodynamic characteristics of two-phase flow.

Unified Model for Gas-Liquid Pipe Flow via Slug Dynamics—Part 1: Model Development

2003 ◽  
Vol 125 (4) ◽  
pp. 266-273 ◽  
Author(s):  
Hong-Quan Zhang ◽  
Qian Wang ◽  
Cem Sarica ◽  
James P. Brill
Keyword(s):  
Flow Pattern ◽  
Pipe Flow ◽  
Slug Flow ◽  
Control Volume ◽  
Model Development ◽  
Flow Patterns ◽  
Hydrodynamic Characteristics ◽  
Momentum Exchange ◽  
Two Phase ◽  
Inclination Angles

A unified hydrodynamic model is developed for predictions of flow pattern transitions, pressure gradient, liquid holdup and slug characteristics in gas-liquid pipe flow at all inclination angles from −90° to 90° from horizontal. The model is based on the dynamics of slug flow, which shares transition boundaries with all the other flow patterns. By use of the entire film zone as the control volume, the momentum exchange between the slug body and the film zone is introduced into the momentum equations for slug flow. The equations of slug flow are used not only to calculate the slug characteristics, but also to predict transitions from slug flow to other flow patterns. Significant effort has been made to eliminate discontinuities among the closure relationships through careful selection and generalization. The flow pattern classification is also simplified according to the hydrodynamic characteristics of two-phase flow.

An Investigation of Slug Flow in Hilly Terrain Pipelines

2001 ◽  
Author(s):  
Suat Bagci ◽  
Adel Al-Shareef
Keyword(s):  
Liquid Film ◽  
Slug Flow ◽  
Flow Characteristics ◽  
Source Model ◽  
Pipe Diameter ◽  
Liquid Holdup ◽  
Hilly Terrain ◽  
Two Phase ◽  
Flow Interactions ◽  
Inclined Pipes

Abstract Two-phase flow in hilly terrain pipelines can cause significant practical operating problems. When slugs flow in a hilly terrain pipeline that contains sections of different inclinations they undergo a change of length and slug flow characteristics as the slug move from section to section. In addition, slugs can be generated at low elbows, dissipate at top elbows and shrink or grow in length as they travel along the pipe. A mathematical model and a computer program was developed to simulate these phenomena. The model was based on the sink/source concept at the pipeline connections. A connection between two pipeline sections of different slopes was conveniently called elbow. An elbow accumulates liquid as a sink, and releases liquid as a source. The sink/source has a characteristic capacity of its own. This capacity is positive if the liquid can indeed be accumulated at the elbow or negative if the liquid is actually drained away from the elbow. This type of treatment effectively isolates the flow upstream from an elbow from that downstream, while still allowing flow interactions between two detailed pipeline sections. The hydrodynamic flow model was also used to calculate the film liquid holdup in horizontal and inclined pipelines. The model can successfully predict the liquid film holdup if the liquid film height is assumed to be uniform through the gas pocket. Many other models were used to calculate all the needed parameters to perform the sink/source model. The overall effect of a hill or terrain on slug flow depends on the operating flow rates and pipeline configurations. For special case of near constant slug frequency corresponding to moderately high superficial liquid and gas velocities, this effect was found to be small. The changes in the film characteristics between two adjacent pipeline sections were found to be mostly responsible for the pseudo-slug generation, slug growth and dissipation in the downstream pipeline sections. The film liquid holdup decreased with increasing pipe diameter. The unit slug length increased at the upstream inclined pipes and decreased at the downstream inclined pipes with increasing pipe diameter. The possibility of pseudo-slug generation was increased at large pipe diameters even at high sink capacities. At low sink capacities, no pseudo-slugs were generated at high superficial velocities. The slug flow characteristics was more effected by low superficial gas and liquid velocities, large pipe diameters and shallow pipeline inclinations.

Transient Two-Phase Flow Model for High Viscous Liquids Over Hilly Terrain

2014 ◽  
Author(s):  
Abraham Parra ◽  
Miguel Asuaje
Keyword(s):  
Slug Flow ◽  
Mechanical Design ◽  
Fluid Model ◽  
Process Equipment ◽  
Maximum Deviation ◽  
Multiphase Model ◽  
Viscous Effects ◽  
Hilly Terrain ◽  
Two Phase ◽  
Wide Range

This paper presents the detailed development of a multiphase model to predict the behavior of terrain-induced slugging, influenced by the viscous effects and hilly terrain. Currently, high viscosity heavy crude oil represents most of the available fossil resources. This crude flows inside long and expensive pipelines, usually over hilly terrain, causing the formation of slug flow. A very common flow pattern produces critical effects on pipelines in terms of modelling, mechanical stress, induced oscillations, fatigue, production losses, and other negative effects for the system. An accurate characterization of this pattern may give critical data for the mechanical design of piping systems and provide valuable information for the downstream process equipment selection. At present, most of the existing models to predict the behavior of slug flow neglect relevant parameters such as the effect of liquid viscosity and the effect of topographic terrain profile. The objective of this study is to present a mechanistic fluid model to determine the behavior of slug flow affected by the hilly terrain using viscous fluids. The model predicts the four stages of slug flow proposed by Schmidt et al. [1], and extends these stages to hilly terrain systems. The model is valid for a wide range of fluid viscosities and considers a range of pipe inclinations between 0° and 90°. Model validation with available literature and experimental data, shows a maximum deviation of 6%.

Unified Model for Gas-Liquid Pipe Flow Via Slug Dynamics: Part 2 — Model Validation

2002 ◽  
Author(s):  
Hong-Quan Zhang ◽  
Qian Wang ◽  
Cem Sarica ◽  
James P. Brill
Keyword(s):  
Experimental Data ◽  
Liquid Flow ◽  
Pipe Flow ◽  
Flow Behavior ◽  
Two Phase ◽  
Flow Rates ◽  
Inclination Angles ◽  
Gas Liquid Flow ◽  
Extensive Experimental Data ◽  
Good Agreement

In Zhang et al. [1], a unified hydrodynamic model is developed for prediction of gas-liquid pipe flow behavior based on slug dynamics. In this study, the new model is validated with extensive experimental data acquired with different pipe diameters, inclination angles, fluid physical properties, gas-liquid flow rates and flow patterns. Good agreement is observed in every aspect of the two-phase pipe flow.

Entrance Effects in a Two-Phase Slug Flow

1962 ◽  
Vol 84 (1) ◽  
pp. 29-38 ◽  
Author(s):  
R. Moissis ◽  
P. Griffith
Keyword(s):  
Slug Flow ◽  
Present Theory ◽  
Separation Distance ◽  
Rise Velocity ◽  
Two Phase ◽  
Developing Flow ◽  
Two Phases ◽  
Kinetics Of ◽  
Theory And Experiments ◽  
Good Agreement

This paper describes quantitatively one stage of the flow development process in equipment working with two-phase mixtures. The kinetics of a Taylor bubble, as it rises behind a series of other bubbles in a gas-liquid slug flow, have been determined. The rise velocity of a bubble is expressed as a function of separation distance from the bubble ahead of it. Using this information, the pattern of development of bubbles which initially enter a tube at regular intervals is determined by means of finite difference calculations. The density and, to a first approximation the pressure drop, of the developing flow are then calculated from continuity considerations. The density distribution in the entrance region is found to be a function of flow rates of the two phases, of distance from the inlet, and of initial bubble size. Density calculated by the present theory is compared with experimental measurements by the present and other investigators. Theory and experiments are in good agreement.

Experimental and Numerical Investigation of Separator Pressure Fluctuation Effect on Terrain Slugging in a Hilly Terrain Two-Phase Flow Pipeline

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Eissa Al-Safran ◽  
Leonidas Kappos ◽  
Cem Sarica
Keyword(s):  
Experimental Data ◽  
Pressure Fluctuation ◽  
Slug Flow ◽  
Flow Behavior ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Pressure Increase ◽  
Hilly Terrain ◽  
Two Phase ◽  
Industrial Operations

Two-phase slug flow in horizontal and near horizontal pipes is a common occurrence in many engineering applications and industrial operations. The objective of this study is to experimentally investigate the effects of separator pressure fluctuations on terrain slugging and slug flow characteristics along and downstream of a hilly terrain pipeline. A further objective is to numerically simulate the flow behavior using a transient multiphase flow simulator to match the simulation predictions with the experimental data. Experimental results revealed that during the separator pressure decline, slug initiation is promoted due to the increase in slip velocity, which enhances the slug initiation mechanisms at the lower elbow. On the other hand, during the separator pressure increase, the analyses show slug suppression. In terms of slug flow characteristics, the mean slug velocity, mean slug length, and maximum slug length increased during the separator pressure decline condition and decreased during the separator pressure increase condition. Furthermore, separator pressure has a significant decreasing effect on slug frequency, maximum slug length, and slug length variance downstream of the hilly terrain section. The statistical analysis shows mixed results of decreasing and increasing trends on mean slug lengths under the fluctuated separator pressure when compared with constant separator pressure conditions. The numerical simulation results showed a close match of liquid holdup downstream of the lower elbow and a fair match at the lower elbow. Furthermore, the model was successful in matching the pressure fluctuation at the lower elbow of the experimental data.

An Experimental Study of Two-Phase Slug Flow in Hilly Terrain Pipelines

1995 ◽  
Vol 10 (04) ◽  
pp. 233-240 ◽  
Author(s):  
Guohua H. Zheng ◽  
J.P. Brill ◽  
Ovadia Shoham
Keyword(s):  
Experimental Study ◽  
Slug Flow ◽  
Hilly Terrain ◽  
Two Phase

scholarly journals Experimental and Numerical Study on Gas-Liquid Flow in Hilly-Terrain Pipeline-Riser Systems

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Zhaoyang He ◽  
Limin He ◽  
Haixiao Liu ◽  
Dan Wang ◽  
Xiaowei Li ◽  
...  
Keyword(s):  
Flow Pattern ◽  
Liquid Flow ◽  
Slug Flow ◽  
Gas Transport ◽  
Numerical Study ◽  
Pipeline System ◽  
Hilly Terrain ◽  
Two Phase ◽  
Gas Liquid Flow ◽  
Stable Flow

In offshore oil and gas transport, gas-liquid mixed transport is a basic flow phenomenon. In general, pipeline undulations are caused by seabed topography; therefore, it is of great significance to study the mechanisms underlying gas and liquid flows in hilly-terrain pipeline-riser systems. This study established a hilly-terrain pipeline-riser experimental system in an indoor laboratory. The flow pattern and its flow mechanism were studied via experimental observation and pressure detection. Experimental results showed that the gas-liquid flow pattern in the hilly-terrain pipeline-riser system can be divided into four types: severe slugging, dual-peak slug, oscillation flow, and stable flow, where dual-peak slug flow is a special flow pattern in this pipeline system. Hilly-terrain units obstruct the downstream gas transport, weaken the gas-liquid eruption in the riser, and increase the cycle of severe slugging. In this paper, gas is regarded as power in the flow of gas and liquid, and the accumulation of liquid in low-lying areas is regarded as an obstacle. Then, the moment of gas-liquid blowout is studied as main research object, and the mechanism of flow pattern transformation is described in detail. This study investigated the accuracy of the OLGA 7.0 simulation results for the gas-liquid two-phase flow in the hilly-terrain pipeline-riser. The results show that OLGA 7.0 achieves a more accurate calculation of severe slugging and stable flow and can predict both the pressure trend and change characteristics. However, the simulation accuracies for dual-peak slug flow and oscillation flow are poor, and the sensitivity to gas changes is insufficient.

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