Compressibility Effects in the Gas Phase for Unsteady Annular Two-Phase Flow in a Microchannel

2006 ◽  
Author(s):  
Alexandru Herescu ◽  
Jeffrey S. Allen
Keyword(s):  
Shock Wave ◽  
Gas Phase ◽  
High Speed ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Flow Behavior ◽  
Flow Section ◽  
Phase Flow ◽  
Two Phase ◽  
Gas Liquid Flow

High speed microscopy experiments investigating two-phase (gas-liquid) flow behavior in capillary-scale systems, that is, systems where capillary forces are important relative to gravitational forces, have revealed a unique unsteady annular flow with periodic destabilization of the gas-liquid interface. Standing waves develop on the liquid film and grow into annular lobes similar with those observed in low-speed two-phase flow. The leading face of the lobe will decelerate and suddenly become normal to the wall of the capillary, suggesting the possibility of a shock wave in the gas phase at a downstream location from the minimum gas flow section. Visualization of the naturally occurring convergent-divergent nozzle-like structures as well as a discussion on the possibility of shock wave formation are presented.

Gas-Liquid Flow Through Horizontal Eccentric Annuli: CFD and Experiments Compared

2011 ◽  
Author(s):  
Mehmet Sorgun ◽  
Reza E. Osgouei ◽  
M. Evren Ozbayoglu ◽  
A. Murat Ozbayoglu
Keyword(s):  
Liquid Flow ◽  
High Speed ◽  
Two Phase Flow ◽  
Flow Behavior ◽  
Flow Patterns ◽  
Phase Flow ◽  
Cfd Model ◽  
Flow Loop ◽  
Two Phase ◽  
Gas Liquid Flow

Although flow of two-phase fluids is studied in detailed for pipes, there exists a lack of information about aerated fluid flow behavior inside a wellbore. This study aims to simulate gas-liquid flow inside horizontal eccentric annulus using an Eulerian-Eulerian computational fluid dynamics (CFD) model for two-phase flow patterns i.e., dispersed bubble, dispersed annular, plug, slug, churn, wavy annular. To perform experiments using air-water mixtures for various in-situ air and water flow rates, a flow loop was constructed. A digital high speed camera is used for recording each test dynamically for identification of the liquid holdup and flow patterns. Results showed that CFD model predicts frictional pressure losses with an error less than 20% for all two-phase flow patterns when compared with experimental data.

Two-Phase Wakes in Adiabatic Liquid-Gas Flow Around a Cylinder

2020 ◽  
Author(s):  
Dohwan Kim ◽  
Matthew J. Rau
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
High Speed ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Water Channel ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Around A Cylinder ◽  
High Heat Transfer

Abstract Small tubes and fins have long been used as methods to increase surface area for convective heat transfer in single-phase flow applications. As demands for high heat transfer effectiveness has increased, implementing evaporative phase-change heat transfer in conjunction with small fins, tubes, and surface structures in advanced heat exchanger and heat sink designs has become increasingly attractive. The complex two-phase flow that results from these configurations is poorly understood, particularly in how the gas phase interacts with the flow structure of the wake created by these bluff bodies. An experimental study of liquid-gas bubbly flow around a cylinder was performed to understand these complex flow physics. A 9.5 mm diameter cylinder was installed horizontally within a vertical water channel facility. A high-speed camera captured the movement of the liquid-gas mixture around the cylinder for a range of bubble sizes. Liquid Reynolds number, calculated based on the cylinder diameter, was varied approximately from 100 to 3000. Time-averaged probability of bubble presence was calculated to characterize the cylinder wake and its effects on the bubble motion. The influence of the liquid Reynolds number, superficial air velocity, and bubble size is discussed in the context of the observed two-phase flow patterns.

Effects of Curved Section on Gas-Liquid Two-Phase Flow in Milli-Channel

2013 ◽  
Author(s):  
Kazuki Takeda ◽  
Shinpei Okamoto ◽  
Kenji Yoshida ◽  
Isao Kataoka
Keyword(s):  
Pressure Loss ◽  
High Speed ◽  
Two Phase Flow ◽  
Flow Behavior ◽  
Narrow Channel ◽  
Phase Flow ◽  
Straight Section ◽  
Industrial Products ◽  
Two Phase ◽  
Curved Section

In recent years, we can easily find the gas-liquid two-phase flow in narrow channel which has straight section and curved section in many industrial products. In order to improve the performance of these industrial products, it is important to clarify the effects of curved section on gas-liquid two-phase flow behavior in narrow channel. In this study, we have measured the pressure loss precisely on straight section and curved section in milli-channel respectively. From the measured pressure loss, we evaluated the mean pressure loss and its intensity. Flow visualization by using high-speed video camera was additionally performed to make clear the relation between modification of pressure loss and flow pattern in curved section. As a result, effects of curved section on gas-liquid two-phase flow in narrow channel were evaluated.

scholarly journals Numerical Simulation of Gas-Particle Two-Phase Flow in a Nozzle with DG Method

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Duan Maochang ◽  
Yu Xijun ◽  
Chen Dawei ◽  
Qing Fang ◽  
Zou Shijun
Keyword(s):  
Flow Field ◽  
Gas Phase ◽  
Mass Fraction ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Governing Equations ◽  
Two Phase ◽  
Dg Method ◽  
The Impact

In this paper, the discontinuous Galerkin (DG) method is applied to solve the governing equations of the dispersed two-phase flow with the two-fluid Euler/Euler approach. The resulting governing equations are simple in form and the solution process is very natural. The characteristics of the gas-particle two-phase flow in an engine nozzle are mainly analyzed, and the impacts of the particle mass fraction and particle size on the flow field and engine performance are evaluated. Because of the addition of particles, the gas flow field undergoes significant modifications. Increase in the mass fraction leads to a significant thrust loss in the gas phase, and the impact of the particles on the gas phase could be substantial. Therefore, a quantitative study of thrust loss in the nozzle due to the particle impact is made. It is found that the gas thrust in the two-phase flow is reduced, but the total thrust of the two-phase flow increases to a certain extent.

Experimental Visualization of Two Phase Flow Inside an Electrical Submersible Pump Stage

2009 ◽  
Author(s):  
Lissett Barrios ◽  
Mauricio Gargaglione Prado
Keyword(s):  
High Speed ◽  
Two Phase Flow ◽  
Flow Behavior ◽  
Bubble Diameter ◽  
Phase Flow ◽  
Submersible Pump ◽  
Bubble Behavior ◽  
Two Phase ◽  
Operational Conditions ◽  
Electrical Submersible Pump

Dynamic multiphase flow behavior inside a mixed flow Electrical Submersible Pump (ESP) has been studied experimentally and theoretically for the first time. The overall objectives of this study are to determine the flow patterns and bubble behavior inside the ESP and to predict the operational conditions that cause surging. An experimental facility has been designed and constructed to enable flow pattern visualization inside the second stage of a real ESP. Special high speed instrumentation was selected to acquire visual flow dynamics and bubble size measurements inside the impeller channel. Experimental data was acquired utilizing two types of tests (surging test and bubble diameter measurement test) to completely evaluate the pump behavior at different operational conditions. A similarity analysis performed for single-phase flow inside the pump concluded that viscosity effects are negligible compared to the centrifugal field effects for rotational speeds higher than 600 rpm. Therefore, the two-phase flow tests were performed for rotational speeds of 600, 900, 1200, and 1500 rpm. Results showed formation of a large gas pocket at the pump intake during surging conditions.

Experimental Visualization of Two-Phase Flow Inside an Electrical Submersible Pump Stage

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Lissett Barrios ◽  
Mauricio Gargaglione Prado
Keyword(s):  
High Speed ◽  
Two Phase Flow ◽  
Flow Behavior ◽  
Bubble Diameter ◽  
Phase Flow ◽  
Submersible Pump ◽  
Bubble Behavior ◽  
Two Phase ◽  
Operational Conditions ◽  
Electrical Submersible Pump

Dynamic multiphase flow behavior inside a mixed flow electrical submersible pump (ESP) has been studied experimentally and theoretically for the first time. The overall objectives of this study are to determine the flow patterns and bubble behavior inside the ESP and to predict the operational conditions that cause surging. An experimental facility has been designed and constructed to enable flow pattern visualization inside the second stage of a real ESP. Special high-speed instrumentation was selected to acquire visual flow dynamics and bubble size measurements inside the impeller channel. Experimental data were acquired utilizing two types of tests (surging test and bubble diameter measurement test) to completely evaluate the pump behavior at different operational conditions. A similarity analysis performed for single-phase flow inside the pump concluded that viscosity effects are negligible compared to the centrifugal field effects for rotational speeds higher than 600 rpm. Therefore, the two-phase flow tests were performed for a rotational speeds of 600, 900, 1200, and 1500 rpm. Results showed formation of a large gas pocket at the pump intake during surging conditions.

Behavior of Bubbles Separated by a Cross-Shaped Obstacle Placed in a Circular Flow Channel

2017 ◽  
Author(s):  
Kazuyuki Takase ◽  
Hiep H. Nguyen ◽  
Gaku Takase ◽  
Yoshihisa Hiraki
Keyword(s):  
High Speed ◽  
Nuclear Reactor ◽  
Two Phase Flow ◽  
Flow Direction ◽  
Flow Behavior ◽  
Bubbly Flow ◽  
Wire Mesh ◽  
Phase Flow ◽  
Two Phase ◽  
Validation Data

Clarifying two-phase flow characteristics in a nuclear reactor core is important in particular to enhance the thermo-fluid safety of nuclear reactors. Moreover, bubbly flow data in subchannels with spacers are needed as validation data for current CFD codes like a direct two-phase flow analysis code. In order to investigate the spacer effect on the bubbly flow behavior in a subchannel of the nuclear reactor, bubble dynamics around the simply simulated spacer was visually observed by a high speed camera. Furthermore, the void fraction and interfacial velocity distributions just behind the simulated spacer were measured quantitatively by using a wire-mesh sensor system with three wire-layers in the flow direction. From the present study, bubble separation behavior dependence upon the spacer shape was clarified.

Numerical Simulation of the Two-Phase Flow in Novel Combined Top and Corner Spray Degassing Tank for Aluminum Melt

2012 ◽  
Vol 510 ◽  
pp. 790-794
Author(s):  
Hui Sun ◽  
Zhi Yong Zhou
Keyword(s):  
Two Phase Flow ◽  
Volume Fraction ◽  
Fluid Model ◽  
Flow Behavior ◽  
Phase Flow ◽  
Gas Velocity ◽  
Two Phase ◽  
Aluminum Melt ◽  
Two Fluid Model ◽  
Gas Liquid Flow

The Eulerian two-fluid model incorporated with the multiple reference frame approach is adopted to predict the gas-liquid two-phase flow in the novel combined top and corner spray degassing tank for aluminum melt. The influence of different parameters, such as gas velocity or hole areas at the tank corners on the gas-liquid flow behavior is also investigated. Results show that little gas emerges near the wall of tank equipped with traditional rotating spray degasser. Using the combined top and corner spray degasser, the distribution of bubbles in the tank, especially near the tank wall, is improved significantly, which advantages the hydrogen removal. With the increasing gas velocity or hole areas at the tank corners, the width of ring zone with low gas volume fraction decreases, and thus enhances the effect of hydrogen removal.

Ultrasound Reflector Recognition and Tracking Technique for Two-Phase Flow

2016 ◽  
Author(s):  
Antonin Povolny ◽  
Hiroshige Kikura
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Nuclear Reactors ◽  
Phase Interface ◽  
Secondary Data ◽  
Phase Flow ◽  
Two Phase ◽  
Tracking Technique ◽  
Measurement Line

Two-phase liquid-gas flow occurs in many safety systems of nuclear reactors as well as in reactor cores. To further improve both safety and commercial performance of nuclear reactors, it is important to improve numerical codes and deepen the understanding of two-phase flow with experiments on gas behaviour in liquids. Among several available measurement methods, ultrasound based methods are affordable and easy to use even for high pressure/temperature flows in non-transparent pipes. Ultrasound Reflector Recognition and Tracking Technique (URRTT) has been developed as a new technique. It uses an ultrasound transducer, which emits ultrasound beam into the liquid with gas bubbles. The phase interface reflects the beam and because of that, the phase interface can be recognised in the reflected signal and the distance (from the transducer) can be calculated. The core of this technique is the tracking algorithm that can separate data of different bubbles from each other and obtain their one dimensional trajectories along the measurement line. Trajectories measured simultaneously by more transducers (at different positions or from different directions) can be combined. That means trajectory of the bubble interface from one transducer can be connected to trajectory from a different transducer and by doing so, a secondary data can be obtained using the information that those trajectories belong to the same bubble. As an example, the average two dimensional velocity between two parallel measurement lines can be obtained. Another example is the measurement of the bubble size using one measurement line with two oppositely oriented transducers. Experiments have been conducted to prove the concept of URRTT. Results have been validated to data obtained by the image processing of footage taken by a high speed camera. The results obtained by URRTT can be of high value since each detected bubble is measured individually and thus, difference in the bubble behaviour based on the size, velocity or history of the bubble can be described.

Periodic Interface Destabilization in High-Speed Gas-Liquid Flows at the Capillary Scale

2006 ◽  
Author(s):  
Alexandru Herescu ◽  
Jeffrey S. Allen
Keyword(s):  
Liquid Film ◽  
High Speed ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Travelling Waves ◽  
Phase Flow ◽  
Capillary Tubes ◽  
Two Phase ◽  
Sequence Of Events ◽  
Number Systems

Recent research efforts have illustrated the importance of capillarity on the behavior of two-phase flow (gas-liquid) in low Bond number systems; that is, systems where capillary forces are important relative to gravitational forces. Such systems include capillary tubes and microchannels as well as the gas flow channels of a PEM fuel cell. High speed microscopy experiments visualizing air-water flow through a 500 micrometer square glass capillary, 10 cm long were conducted. The flow rates are significant with velocities of 6.2 m/s for the air and 0.2 m/s for the water. A unique annular flow with periodic destabilization of the gas-liquid interface has been observed. Standing waves develop on the liquid film and grow into annular lobes typical of that observed in low speed two-phase flow in capillary tubes. Atypical is the interface destabilization phenomena. The leading face of the lobe will decelerate and suddenly become normal to the wall of the square capillary while the trailing face of the lobe will remain gently sloped back into the annular liquid film. The transition between the leading and trailing faces acquires a sharp edge having a exceptionally large curvature. The entire structure then rapidly collapses and produces travelling waves which propagate upstream and downstream along the annular liquid film. The entire sequence of events takes approximately a half millisecond. This destabilization phenomenon is regular and periodic. Visualization of the destabilization from the high speed microscopy setup and preliminary analysis are presented.

Sign in / Sign up

Export Citation Format

Share Document