Vibration Behavior of Marine Risers Conveying Gas-Liquid Two-Phase Flow

2015 ◽  
Author(s):  
Chen An ◽  
Jian Su
Keyword(s):  
Dynamic Behavior ◽  
Slug Flow ◽  
Structural Model ◽  
Two Phase Flow ◽  
Integral Transform ◽  
Internal Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Marine Risers ◽  
Vibration Behavior

Vortex-induced vibration (VIV) has been intensively studied both theoretically and experimentally due to its importance in the design of marine risers. In recently years, the effects of single phase, steady internal flow on the VIV of marine risers have received increasing attention. However, the effects of transient two-phase flow on the vibration behavior of marine risers have been seldom studied. In this work, a fluid-structural model for analyzing the dynamic behavior of riser vibration subjected to simultaneous internal gas-liquid two-phase flow and external marine current is proposed. Slug flow regime is considered as it causes most violent vibrations. An analytical model is adopted for the prediction of important flow characteristics of the gas-liquid slug flow. A wake oscillator is employed to model the vortex shedding behind the riser. The dynamic behavior of risers is analytically and numerically investigated by using the generalized integral transform technique (GITT), by which the transverse vibration equation is transformed into a coupled system of second order differential equations in the temporal variable. Parametric studies are performed to analyze the effects of the superficial velocities of liquid and gas on the dynamic behavior of risers.

Vibration Behavior of Pipelines Conveying Gas-Liquid Two-Phase Flow Supported on the Seabed

2016 ◽  
Author(s):  
Chen An ◽  
Menglan Duan ◽  
Jian Su
Keyword(s):  
Dynamic Behavior ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Integral Transform ◽  
Transverse Displacement ◽  
Phase Flow ◽  
Liquid Slug ◽  
Two Phase ◽  
Good Convergence ◽  
Vibration Behavior

Pipe-soil interaction has been intensively investigated both theoretically and experimentally due to its importance in the design of seabed pipelines. In recently years, the effects of single phase, steady internal flow on the dynamic response of seabed pipelines have received increasing attention. However, the effects of transient two-phase flow on the vibration behavior of seabed pipelines have been seldom studied. In this work, a physical model for analyzing the dynamic behavior of a seabed pipeline conveying gas-liquid two-phase flow is proposed. Slug flow regime is considered as it causes most violent vibrations. An analytical model is adopted for the prediction of important flow characteristics of the gas-liquid slug flow. The dynamic behavior of pipelines is analytically and numerically investigated by using the generalized integral transform technique (GITT), by which the transverse vibration equation is transformed into a coupled system of second order differential equations in the temporal variable. Good convergence behavior of the proposed eigenfunction expansions is demonstrated for calculating the transverse displacement at various points of pipelines conveying gas-liquid slug flow. Parametric studies are performed to analyze the effect of the internal two-phase flow on the dynamic behavior of pipelines.

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.

Fluctuating Forces in U-Tubes Subjected to Internal Two-Phase Flow

2005 ◽  
Author(s):  
Jean-Luc Riverin ◽  
Michel J. Pettigrew
Keyword(s):  
Two Phase Flow ◽  
Periodic Structures ◽  
Internal Flow ◽  
Resonance Phenomenon ◽  
Dimensionless Frequency ◽  
Phase Flow ◽  
Two Phase ◽  
Power Spectral ◽  
Wide Range ◽  
Periodic Components

Severe in-plane vibrations were observed in a series of 20-mm dia. PVC vertical U-tubes of different elbow geometries subjected to air-water internal flow. An experimental study was undertaken to investigate the excitation mechanism. Vibration response, excitation forces and fluctuating properties of two-phase flow were measured over a wide range of flow conditions. The experimental results show that the observed vibrations are due to a resonance phenomenon between periodic momentum flux fluctuations of two-phase flow and the first modes of U-tubes. The excitation forces consist of a combination of narrow-band and periodic components, with a predominant frequency that increases proportionally to flow velocity. For a given void fraction, the force spectra for various flow velocities and elbow geometries coincide generally well on a plot of the normalized power spectral density as a function of a dimensionless frequency. The predominant frequencies of excitation agree with recent results on the characteristics of periodic structures in two-phase flow.

Study of the 90° Elbows Performance as Phase Separators in an Air-Water Two-Phase Flow

2003 ◽  
Author(s):  
Valente Herna´ndez P. ◽  
Florencio Sa´nchez S. ◽  
Miguel Toledo V. ◽  
Georgiy Polupan
Keyword(s):  
Phase Separation ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Pressure Gradients ◽  
Two Phase ◽  
Branch Diameter ◽  
Independent Variables ◽  
Inclination Angles ◽  
Phase Separator

In order to observe the 90° elbows performance as phase separators in an air-water two-phase flow, experimental results for the phase split which occurs at a 90° branched elbow are presented. The branched elbow geometry was varied in order to have three (branch diameter / elbow diameter) ratios and three branch inclination angles. Also the pressure was monitored at different points of the elbow with ramification in order to examine the pressure drop effect. The flow pattern upstream was mainly slug flow. First, the analysis of the main independent variables effect, (superficial velocities, branch inclination angle, ratio of diameters and pressure gradients) was carried out, then a correlation for the phase split was developed and, finally a comparison was made with data of phase separation in T junctions obtained by Azzopardi [1] and Soliman [2], as a result, a better behavior as phase separator was found for the elbow.

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.

scholarly journals Dynamics of a two-phase flow through a minichannel: Transition from churn to slug flow

2016 ◽  
Vol 131 (4) ◽  
Author(s):  
Grzegorz Górski ◽  
Grzegorz Litak ◽  
Romuald Mosdorf ◽  
Andrzej Rysak
Keyword(s):  
Slug Flow ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Through

Analysis of Turbulence Structure and Void Fraction Distribution in Gas-Liquid Two-Phase Flow Under Bubbly and Slug Flow Regime

2011 ◽  
Author(s):  
Isao Kataoka ◽  
Kenji Yoshida ◽  
Tsutomu Ikeno ◽  
Tatsuya Sasakawa ◽  
Koichi Kondo
Keyword(s):  
Void Fraction ◽  
Turbulence Model ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Bubbly Flow ◽  
Turbulence Structure ◽  
Phase Flow ◽  
Two Phase ◽  
Void Fraction Distribution ◽  
Fraction Distribution

Accurate analyses of turbulence structure and void fraction distribution are quite important in designing and safety evaluation of various industrial equipments using gas-liquid two-phase flow such as nuclear reactor, etc. Using turbulence model of two-phase flow and models of bubble behaviors in bubble flow and slug flow, systematic analyses of distributions of void fraction, averaged velocity and turbulent velocity were carried out and compared with experimental data. In bubbly flow, diffusion of bubble and lift force are dominant in determining void fraction distribution. On the other hand, in slug flow, large scale turbulence eddies which convey bubbles into the center of flow passage are important in determining void fraction distribution. In turbulence model, one equation turbulence model is used with turbulence generation and turbulence dissipation due to bubbles. Mixing length due to bubble is also modeled. Using these bubble behavior models and turbulence models, systematic predictions were carried out for void distributions and turbulence distributions for wide range of flow conditions of two phase flow including bubbly and slug flow. The results of predictions were compared with experimental data in round straight tube with successful agreement. In particular, concave void distributions in bubbly flow and convex distribution in slug flow were well predicted based on the present model.

Research Analysis and Experiment Study on Flow Field of Hydrodynamic Coupling

2011 ◽  
Vol 418-420 ◽  
pp. 2006-2011
Author(s):  
Rui Zhang ◽  
Cheng Jian Sun ◽  
Yue Wang
Keyword(s):  
Flow Field ◽  
Cfd Simulation ◽  
Two Phase Flow ◽  
Three Dimensional ◽  
Internal Flow ◽  
Phase Flow ◽  
Complex Flow ◽  
Two Phase ◽  
Operation Conditions ◽  
Hydrodynamic Coupling

CFD simulation and PIV test technology provide effective solution for revealing the complex flow of hydrodynamic coupling’s internal flow field. Some articles reported that the combination of CFD simulation and PIV test can be used for analyzing the internal flow field of coupling, and such analysis focuses on one-phase flow. However, most internal flow field of coupling are gas-fluid two-phase flow under the real operation conditions. In order to reflect the gas-fluid two-phase flow of coupling objectively, CFD three-dimensional numerical simulation is conducted under two typical operation conditions. In addition, modern two-dimensional PIV technology is used to test the two-phase flow. This method of combining experiments and simulation presents the characteristics of the flow field when charging ratios are different.

An Experimental Study on Air-Water Two-Phase Flow Patterns in Pebble Beds

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Bai Bofeng ◽  
Liu Maolong ◽  
Su Wang ◽  
Zhang Xiaojie
Keyword(s):  
Experimental Study ◽  
Flow Pattern ◽  
Test Section ◽  
Slug Flow ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Pattern Transition

An experimental study was conducted on the air-water two-phase flow patterns in the bed of rectangular cross sections containing spheres of regular distribution. Three kinds of glass spheres with different diameters (3 mm, 6 mm, and 8 mm) were used for the establishment of the test section. By means of visual observations of the two-phase flow through the test section, it was discovered that five different flow patterns occurred within the experimental parameter ranges, namely, bubbly flow, bubbly-slug flow, slug flow, slug-annular flow, and annular flow. A correlation for the bubble and slug diameter in the packed beds was proposed, which was an extended expression of the Tung/Dhir model, Jamialahmadi’s model, and Schmidt’s model. Three correlations were proposed to calculate the void friction of the flow pattern transition in bubble flow, slug flow, and annular flow based on the bubble model in the pore region. The experimental result showed that the modified Tung and Dhir model of the flow pattern transition was in better agreement with the experimental data compared with Tung and Dhir’s model.

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