Fluctuation of Air-Water Two-Phase Flow in Horizontal and Inclined Water Pipelines

2005 ◽  
Vol 129 (1) ◽  
pp. 1-14 ◽  
Author(s):  
A. R. Kabiri-Samani ◽  
S. M. Borghei ◽  
M. H. Saidi
Keyword(s):  
Slug Flow ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Digital Camera ◽  
Air Entrainment ◽  
Maximum Pressure ◽  
Water Mixture ◽  
Two Phase ◽  
Cross Sectional ◽  
Pressure Transducers

Air in water flow is a frequent phenomenon in hydraulic structures. The main reason for air entrainment is vortices at water intakes, pumping stations, tunnel inlets, and so on. The accumulated air, in a conduit, can evolve to a different flow pattern, from stratified to pressurized. Among different patterns, slug is most complex with extreme pressure variations. Due to lack of firm relations between pressure and influential parameters, study of slug flow is very important. Based on an experimental model, pressure fluctuations inside a circular, horizontal, and inclined pipe (90mm inside diameter and 10m long) carrying tow-phase air-water slug flow has been studied. Pressure fluctuations were sampled simultaneously at different sections, and longitudinal positions. The pressure fluctuations were measured using differential pressure transducers (DPT), while behavior of the air slug was studied using a digital camera. The objective of the paper is to predict the pressure variation in a pipeline or tunnel, involving resonance and shock waves experimentally. The results show that the more intensive phase interaction commences stronger fluctuations. It is shown, that the air-water mixture entering the pipe during rapid filling of surcharging can cause a tremendous pressure surge in the system and may eventually cause failure of the system (e.g., the maximum pressure inside the pipe would reach up to 10 times of upstream hydrostatic pressure as suggested by others too). Relations for forecasting pressure in these situations are presented as a function of flow characteristics, pipe geometry, longitudinal, and cross-sectional positions and head water.

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.

Pressure Loss in a Horizontal Two-Phase Slug Flow

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
A. R. Kabiri-Samani ◽  
S. M. Borghei
Keyword(s):  
Slug Flow ◽  
Pressure Loss ◽  
Flow Characteristics ◽  
Transient Pressure ◽  
Air Concentration ◽  
Two Phase ◽  
Sewer Pipes ◽  
Pressure Transducers ◽  
And Shock Waves ◽  
Pumping Stations

The study of air-water, two-phase flows in hydraulic structures such as pressurized flow tunnels, culverts, sewer pipes, junctions, and similar conduits is of great importance for design purposes. Air can be provided by vortices at water intakes, pumping stations, aerators, steep channels, etc. Under certain conditions, air may also be introduced into pressurized intake systems, which may form large bubbles in portions of the pipe. The bubbles may, in turn, cause an unstable slug flow, or other flow patterns, that leads to sever periodic transient pressure. In this paper, an experimental model (a circular and transparent pipeline, 90 mm in ID and 10 m in length) is used to predict pressure loss in a pipeline or tunnel involving resonance and shock waves introduced by a two-phase air-water slug flow. For this purpose, differential pressure transducers were used to measure pressure loss variations in time along the pipeline at different sections and for different air/water flow rates. The experimental results of pressure loss for different hydraulic and geometric properties indicate that Weber number (We), Froude number (Fr), and air concentration (C) are the most important parameters affecting pressure loss. Finally, relations for forecasting pressure loss in these situations are presented as a function of flow characteristics.

Flow Characteristics of Adiabatic Gas-Liquid Two-Phase Flow in a Horizontal Flat Rectangular Microchannel

2011 ◽  
Author(s):  
Hideo Ide ◽  
Kentaro Satonaka ◽  
Tohru Fukano
Keyword(s):  
Void Fraction ◽  
Slug Flow ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Flow Characteristics ◽  
Flow Patterns ◽  
Phase Flow ◽  
Similar Data ◽  
Two Phase ◽  
The Mean

Experiments were performed to obtain, analyze and clarify the mean void fraction, the mean liquid holdup, and the liquid slug velocity and the air-water two-phase flow patterns in horizontal rectangular microchannels, with the dimensions equal to 1.0 mm width × 0.1 mm depth, and 1.0 mm width × 0.2 mm depth, respectively. The flow patterns such as bubble flow, slug flow and annular flow were observed. The microchannel data showed similar data patterns compared to those in minichannels with the width of 1∼10mm and the depth of 1mm which we had previously reported on. However, in a 1.0 × 0.1 mm microchannel, the mean holdup and the base film thickness in annular flow showed larger values because the effects of liquid viscosity and surface tension on the holdup and void fraction dominate. The remarkable flow characteristics of rivulet flow and the flow with a partial dry out of the channel inner wall were observed in slug flow and annular flow patterns in the microchannel of 0.1 mm depth.

The Study of Dynamic Slug Flow Characteristics Using Digital Image Analysis—Part I: Flow Visualization

1998 ◽  
Vol 120 (2) ◽  
pp. 97-101 ◽  
Author(s):  
M. Gopal ◽  
W. P. Jepson
Keyword(s):  
Image Analysis ◽  
Digital Image ◽  
Slug Flow ◽  
Digital Image Analysis ◽  
Flow Characteristics ◽  
Liquid Mixtures ◽  
Pipeline System ◽  
Two Phase ◽  
Analysis Techniques ◽  
Image Analysis Techniques

This paper reports the application of novel, digital image analysis techniques in the study of slug flow characteristics, under dynamic conditions in two-phase gas-liquid mixtures. Water and an oil of viscosity 18 cP were used for the liquid phase and carbon dioxide was used for the gas phase. Flow in a 75-mm i.d., 10-m long acrylic pipeline system was studied. Images of slugs were recorded on video by S-VHS cameras, using an audio-visual mixer. Each image was then digitized frame-by-frame and analyzed on a SGI™ workstation. Detailed slug characteristics, including liquid film heights, slug translational velocity, mixing length, and, slug length, were obtained.

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.

Numerical Simulation of Two-Phase Slug Flows in Microchannels

2009 ◽  
Author(s):  
A. Mehdizadeh ◽  
S. A. Sherif ◽  
W. E. Lear
Keyword(s):  
Surface Tension ◽  
Slug Flow ◽  
Stokes Equations ◽  
Pressure Fluctuations ◽  
Water Interface ◽  
Liquid Slug ◽  
Complex Flow ◽  
Two Phase ◽  
Air Water Interface ◽  
Slug Flows

In this paper the Navier-stokes equations for a single liquid slug have been solved in order to predict the circulation patterns within the slug. Surface tension effects on the air-water interface have been investigated by solving the Young–Laplace equation. The calculated interface shape has been utilized to define the liquid slug geometry at the front and tail interfaces of the slug. Then the effects of the surface tension on the hydrodynamics of the two-phase slug flow have been compared to those where no surface tension forces exist. The importance of the complex flow field features in the vicinity of the two interfaces has been investigated by defining a non-dimensional form of the wall shear stress. The latter quantity has been formulated based on non-dimensional parameters in order to define a general Moody friction factor for typical two-phase slug flows in microchannels. Moreover, the hydrodynamics of slug flow formation has been examined using computational fluid dynamics (CFD). The volume-of-fluid (VOF) method has been applied to monitor the growth of the instability at the air-water interface. The lengths of the slugs have been correlated to the pressure fluctuations in the mixing region of the air and water streams at an axisymmetric T-junction. The main frequencies of the pressure fluctuations have been investigated using the Fast Fourier Transform (FFT) method.

Transition simulation of two-phase intermittent slug flow characteristics in oil and gas pipelines

2020 ◽  
Vol 113 ◽  
pp. 104534 ◽  
Author(s):  
Yicheng Li ◽  
Mirollah Hosseini ◽  
Hossein Arasteh ◽  
Davood Toghraie ◽  
Sara Rostami
Keyword(s):  
Slug Flow ◽  
Oil And Gas ◽  
Flow Characteristics ◽  
Gas Pipelines ◽  
Two Phase ◽  
Oil And Gas Pipelines

scholarly journals 3D Reconstruction of Slug Flow in Mini-Channels with a Simple and Low-Cost Optical Sensor

Sensors ◽  
2019 ◽  
Vol 19 (20) ◽  
pp. 4573
Author(s):  
Huajun Li ◽  
Yandan Jiang ◽  
Haifeng Ji ◽  
Guangyu Liu ◽  
Shanen Yu
Keyword(s):  
3D Reconstruction ◽  
Optical Sensor ◽  
Slug Flow ◽  
Low Cost ◽  
Phase Flow ◽  
Two Phase ◽  
Cross Sectional ◽  
3D Images ◽  
Mini Channels ◽  
2D Images

The present work provides a new approach for 3D image reconstruction of gas-liquid two-phase flow (GLF) in mini-channels based on a new optical sensor. The sensor consists of a vertical and a horizontal photodiode array. Firstly, with the optical signals obtained by the vertical array, a measurement model developed by Support Vector Regression (SVR) was used to determine the cross-sectional information. The determined information was further used to reconstruct cross-sectional 2D images. Then, the gas velocity was calculated according to the signals obtained by the horizontal array, and the spatial interval of the 2D images was determined. Finally, 3D images were reconstructed by piling up the 2D images. In this work, the cross-sectional gas-liquid interface was considered as circular, and high-speed visualization was utilized to provide the reference values. The image deformation caused by channel wall was also considered. Experiments of slug flow in a channel with an inner diameter of 4.0 mm were carried out. The results verify the feasibility of the proposed 3D reconstruction method. The proposed method has the advantages of simple construct, low cost, and easily multipliable. The reconstructed 3D images can provide detailed and undistorted information of flow structure, which could further improve the measurement accuracy of other important parameters of gas-liquid two-phase flow, such as void fraction, pressure drop, and flow pattern.

A Fully Developed Two-Phase Flow Model in Vertical Channels for Bubbly and Slug Flow Regimes

2000 ◽  
Author(s):  
Samir Moujaes ◽  
Erika Sleight
Keyword(s):  
Slug Flow ◽  
Flow Model ◽  
Channel Model ◽  
Rectangular Channel ◽  
Flow Characteristics ◽  
Phase Flow ◽  
Upward Flow ◽  
Circular Channel ◽  
Two Phase ◽  
Comparison Of The Results

Abstract A theoretical model for steady state two-phase vertical upward flow in cylindrical channels is presented. A comparison of the results of this model for a circular channel as well as a reformulated rectangular channel model is partially made with experimental data in the literature. It shows that in general the model predicts the flow characteristics somewhat better in the bubbly regime than the slug flow indicating the need to look further into some of the constitutive relationships used to close the model in this regime.

scholarly journals A Comparative Study on Centrifugal Pump Designs and Two-Phase Flow Characteristic under Inlet Gas Entrainment Conditions

Energies ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 65 ◽  
Author(s):  
Qiaorui Si ◽  
Gérard Bois ◽  
Minquan Liao ◽  
Haoyang Zhang ◽  
Qianglei Cui ◽  
...  
Keyword(s):  
Pressure Pulsation ◽  
Two Phase Flow ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Phase Flow ◽  
Water Mixture ◽  
Centrifugal Pumps ◽  
Two Phase ◽  
Void Fractions

Capability for handling entrained gas is an important design consideration for centrifugal pumps used in petroleum, chemistry, nuclear applications. An experimental evaluation on their two phase performance is presented for two centrifugal pumps working under air-water mixture fluid conditions. The geometries of the two pumps are designed for the same flow rate and shut off head coefficient with the same impeller rotational speed. Overal pump performance and unsteady pressure pulsation information are obtained at different rotational speeds combined with various inlet air void fractions (α0) up to pump stop condition. As seen from the test results, pump 2 is able to deliver up to 10% two-phase mixtures before pump shut-off, whereas pump 1 is limited to 8%. In order to understand the physics of this flow phenomenon, a full three-dimensional unsteady Reynolds Average Navier-Stokes (3D-URANS) calculation using the Euler–Euler inhomogeneous method are carried out to study the two phase flow characteristics of the model pump after corresponding experimental verification. The internal flow characteristics inside the impeller and volute are physically described using the obtained air distribution, velocity streamline, vortex pattern and pressure pulsation results under different flow rates and inlet void fractions. Pump performances would deteriorate during pumping two-phase mixture fluid compared with single flow conditions due to the phase separating effect. Some physical explanation about performance improvements on handing maximum acceptable inlet two phase void fractions capability of centrifugal pumps are given.

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