Numerical investigation on effects of interphase force closures on liquid-phase turbulence and microbubbles distribution in vertical upward channel bubbly flow

2011 ◽  
Vol 7 (4) ◽  
pp. 486-501 ◽  
Author(s):  
Mingjun Pang ◽  
Jinjia Wei ◽  
Bo Yu
Keyword(s):  
Liquid Phase ◽  
Numerical Investigation ◽  
Bubbly Flow ◽  
Interphase Force

Self Organized Structure of Microbubble Plume in a Thin Fluid Layer

2011 ◽  
Author(s):  
Yoshihito Miyagishima ◽  
Tomoaki Watamura ◽  
Yuji Tasaka ◽  
Yuichi Murai
Keyword(s):  
Liquid Phase ◽  
Large Scale ◽  
Fluid Layer ◽  
Bubbly Flow ◽  
The Self ◽  
Bubbly Flows ◽  
Bubble Plume ◽  
Accumulation Pattern ◽  
Thin Fluid ◽  
Self Organized

This study aims to clarify the self-organized structure of microbubble plume as a result of two-way interaction between microbubbles and a flow of the surrounding liquid medium. We observed a sequence on a development of microbubble plumes in a thin fluid layer. Here the microbubbles show accumulation pattern with a different wavenumber depending on the height in the vessel. Variation of spatial wavenumber in the developing process was determined from visualization images, and three areas were distinguished in this process; (1) the area of rising microbubbles with a large wavenumber in a horizontal direction without time dependence; (2) the area of forming a large-scale flow structure, called ‘microbubble plume’ here, which keeps the primary information, horizontal wavenumber of the bubble accumulation with a large wavenumber; (3) the area where the microbubble distribution takes a smaller wavenumber and makes vertical accumulation pattern inside the bubbly flow that is due to the mutual interaction between rising microbubbles and a flow induced by bubbles. To clarify these mutual interactions between liquid and gas phases, we visualized fluid motion of the liquid phase around the microbubble plumes by laser induced fluorescence, LIF. In this way, swaying motions on the tip of rising up bubble plume and liquid phase entrainment into the bubble plumes were visualized. We found the mechanisms for the creation of the self-organized distribution of microbubbles in bubbly flows and its temporal change as the result of the interaction between gas and liquid phase motions in bubbly flows.

Effect of Rheological Properties of Yield Pseudoplastic Fluids on Slugs Characteristics in an Upward Vertical Pipe: Experiments and Modeling

2020 ◽  
Author(s):  
Abdalsalam Ihmoudah ◽  
Mohamed M. Awad ◽  
Mohammad Azizur Rahman ◽  
Stephen D. Butt
Keyword(s):  
Liquid Phase ◽  
Rheological Properties ◽  
Numerical Investigation ◽  
Two Phase Flow ◽  
Immiscible Fluids ◽  
Newtonian Fluids ◽  
Phase Flow ◽  
Vertical Pipe ◽  
Two Phase ◽  
Pseudoplastic Fluids

Abstract Two-phase flow of gas/yield Pseudoplastic fluids can be found in different industrial applications like the chemical processes, oil industry, and petroleum transport in pipelines. In this study, experimental and numerical investigation of the influence of Rheological properties of non-Newtonians fluids in two-phase flow (gas/yield Pseudoplastic fluids) on slug characteristics in an upward vertical flow were performed. Different concentrations of Xanthan gum solutions (0.05%, 0.10%, and 0.15%, by w/w), which are referred to as non-Newtonian, yield Pseudoplastic behavior used as the working liquids and air as a gas. The experiments were conducted in an open-loop re-circulating system has a total length of 65 m to ensure phase mixing, and authorize flow regime patterns to develop. The vertical pipe has a diameter of 76.3 mm. API-compliant 8-speed rotational viscometer model 800 was used to measure the rheological properties of non-Newtonian fluids. Flow visualization and recording videos were achieved by A high-speed camera to a comparison between behavior of Newtonian and non-Newtonian fluids in the two-phase model. Pressure transducers used to measure high-response pressure. Computational fluid dynamics software (ANSYS fluent 2019 R3) was used for the numerical investigation. The volume of fluid (VOF) model has been chosen for tracking immiscible fluids. CFD simulation results compared to the experimental data. The slug behavior and shape were noticed to be affected by changing the rheological properties of the liquid phase. with increasing XG concentration at the same operations conditions, we found that non-uniform and random distribution of small bubbles due to the effective viscous force of a liquid phase.

Development of Prediction Technology of Two-Phase Flow Dynamics Under Earthquake Acceleration — (5) Measurement of Bubble Deformation Near Wall Under Structure Vibration

2012 ◽  
Author(s):  
Kousuke Mizuno ◽  
Akiko Kaneko ◽  
Hideaki Monji ◽  
Yutaka Abe ◽  
Hiroyuki Yoshida ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Flow Structure ◽  
Test Section ◽  
High Speed ◽  
Bubbly Flow ◽  
Oscillation Amplitude ◽  
Reactor Core ◽  
Two Phase ◽  
Piv Measurement ◽  
Structure Vibration

In a nuclear power plant, one of the important issues is evaluation of the safety of reactor core and its pipes when an earthquake occurs. Many researchers have conducted studies on constructions of plants. Consequently, there is some knowledge about earthquake-resisting designs. However the influence of an earthquake vibration on thermal fluid inside a nuclear reactor plant is not fully understood. Especially, there are little knowledge how coolant in a core response when large earthquake acceleration is added. Some studies about the response of fluid to the vibration were carried out. And it is supposed that the void fraction or the power of core is fluctuated with the oscillation by the experiments and numerical analysis. However detailed mechanism about a kinetic response of gas and liquid phases is not enough investigated, therefore the aim of this study is to clarify the influence of vibration of construction on bubbly flow structure. In order to investigate it, we visualize changing of bubbly flow structure in pipeline on which sine wave is applied. Bubbly flow is produced with injecting gas into liquid flow through a horizontally circular pipe. In order to vibrate the test section, the oscillating table is used. The frequency of vibration added from the table is from 1.0 Hz to 10 Hz and acceleration is from 0.4 G to 1 G (1 G = 9.8 m/s2). The test section and a high speed video camera are fixed on the table. Thus the relative velocity between the camera and the test section is ignored. In the visualization experiment, the PIV measurement is conducted. Then the motion of bubbles, for example the shape, the positions and the velocity are measured with observation. In addition, by varying added oscillation amplitude, frequency and flow rate of the fluids, the correlation between these parameters and bubble motion was evaluated. It was clarified that the behavior of liquid phase and bubble through horizontal circular pipes was affected by an oscillation. When structure vibration affects the flow, two main mechanisms are supposed. One is the addition of body force of the oscillation acceleration to liquid phase and bubble, and the other is the velocity oscillation of the test section and the effect of the boundary layer of the pipe wall. It was also found that when the added oscillation frequency and amplitude was changed, the degree of the fluctuation of liquid phase and bubble motions were changed.

Void Fraction Effect on Added Mass in Bubbly Flow

2014 ◽  
Author(s):  
C. Béguin ◽  
É. Pelletier ◽  
S. Étienne
Keyword(s):  
Liquid Phase ◽  
Void Fraction ◽  
Bubbly Flow ◽  
Added Mass ◽  
Bubbly Flows ◽  
Averaged Equations ◽  
Mass Coefficient ◽  
Spherical Bubbles ◽  
Closure Relations ◽  
Added Mass Coefficient

This paper proposes a relation for the added mass coefficient of spherical bubbles depending on void fraction based on results obtained by a semi-analytical method. This information is essential to completely characterize finely dispersed bubbly flows, where small spherical gas bubbles are present in a continuous liquid phase. Most of the closure relations for Euler-Euler or Euler-Lagrange models are obtained from experiments involving single bubbles. Their applicability to systems with high void fraction is therefore questionable. This paper uses solid harmonics to solve 3D potential flow around bubbles. Several configurations were calculated for different numbers of particles and spatial arrangements. Our results are compared with previous studies. Depending on the model proposed by previous authors, added mass forces could increase or decrease with the void fraction. This paper solves these discrepancies. The main purpose of this work is to develop simple formulas fitting our semi-analytical results. These simple formulas are suitable for further use, particularly as added mass models for multiphase flow averaged equations.

Turbulent flow structure and heat transfer in an inclined bubbly flow. Experimental and numerical investigation

2017 ◽  
Vol 52 (1) ◽  
pp. 115-127 ◽  
Author(s):  
A. E. Gorelikova ◽  
O. N. Kashinskii ◽  
M. A. Pakhomov ◽  
V. V. Randin ◽  
V. I. Terekhov ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Numerical Investigation ◽  
Flow Structure ◽  
Bubbly Flow ◽  
Turbulent Flow Structure
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