scholarly journals Vortex Simulation of the Bubbly Flow around a Hydrofoil

2007 ◽  
Vol 2007 ◽  
pp. 1-9 ◽  
Author(s):  
Tomomi Uchiyama ◽  
Tomohiro Degawa
Keyword(s):  
Volume Fraction ◽  
Bubbly Flow ◽  
Bubble Diameter ◽  
Flow Analysis ◽  
Vortex Method ◽  
Bubble Motion ◽  
Two Phase ◽  
Vortex Element ◽  
Dimensional Simulation ◽  
Free Turbulent Flow

This study is concerned with the two-dimensional simulation for an air-water bubbly flow around a hydrofoil. The vortex method, proposed by the authors for gas-liquid two-phase free turbulent flow in a prior paper, is applied for the simulation. The liquid vorticity field is discrerized by vortex elements, and the behavior of vortex element and the bubble motion are simultaneously computed by the Lagrangian approach. The effect of bubble motion on the liquid flow is taken into account through the change in the strength of vortex element. The bubbly flow around a hydrofoil of NACA4412 with a chord length 100 mm is simulated. The Reynolds number is2.5×105, the bubble diameter is 1 mm, and the volumetric flow ratio of bubble to whole fluid is 0.048. It is confirmed that the simulated distributions of air volume fraction and pressure agree well with the trend of the measurement and that the effect of angle of attack on the flow is favorably analyzed. These demonstrate that the vortex method is applicable to the bubbly flow analysis around a hydrofoil.

Numerical Prediction for the Bubbly Flow Around a Hydrofoil by Vortex Method

2007 ◽  
Author(s):  
Tomomi Uchiyama ◽  
Tomohiro Degawa
Keyword(s):  
Numerical Simulation ◽  
Bubbly Flow ◽  
Bubble Diameter ◽  
Flow Analysis ◽  
Vortex Method ◽  
Phase Flow ◽  
Two Dimensional ◽  
Flow Ratio ◽  
Two Phase ◽  
Flow Features

This study is concerned with the numerical simulation for an air-water bubbly flow around a hydrofoil. The two-dimensional vortex method for bubbly flow, proposed by the authors in a prior paper, is applied for the simulation. A hydrofoil of NACA4412 with a chord length 100mm is mounted in an air-water bubbly flow. The Reynolds number is 2.5×105, the bubble diameter is 1 mm, and the volumetric flow ratio of bubble to whole fluid is 0.048. The simulation demonstrates that the two-phase flow features around the hydrofoil are successfully captured and that the vortex method is indeed applicable to the bubbly flow analysis around a hydrofoil.

Three-Dimensional Vortex Method for the Simulation of Bubbly Flow

2010 ◽  
Vol 132 (10) ◽  
Author(s):  
Tomomi Uchiyama ◽  
Shoji Matsumura
Keyword(s):  
Large Scale ◽  
Bubbly Flow ◽  
Three Dimensional ◽  
Vortex Method ◽  
Bubble Motion ◽  
Bubble Plume ◽  
Vorticity Field ◽  
Buoyant Force ◽  
Hydrogen Bubbles ◽  
Vortex Element

This study proposes a three-dimensional vortex method for the simulation of bubbly flow. The method discretizes the vorticity field by vortex elements. The behavior of the vortex element and the bubble motion are simultaneously analyzed with the Lagrangian approach to compute the time evolution of the flow. This study also applies the vortex method to the simulation of a bubble plume to demonstrate the validity of the method. In a tank containing water, small hydrogen bubbles are released from the bottom of the tank. The bubbles rise due to the buoyant force and induce the water flow around them. The simulation for the plume at the starting period highlights that the rising bubbles induce large-scale eddies at their top and that the bubbles are entrained into the eddies. The simulation for the developed plume demonstrates that large-scale eddies appear around the rising bubbles and that they cause the meandering behavior of the plume. Such three-dimensional features of the bubble plume are favorably compared with the experimental results, indicating the validity of the proposed vortex method.

scholarly journals Flow analysis of particulate suspension on an asymmetric peristaltic motion in a curved configuration with heat and mass transfer

2018 ◽  
Vol 19 (4) ◽  
pp. 401 ◽  
Author(s):  
Ahmed Zeeshan ◽  
Nouman Ijaz ◽  
Muhammad Mubashir Bhatti
Keyword(s):  
Volume Fraction ◽  
Biological Fluids ◽  
Particle Volume Fraction ◽  
Flow Analysis ◽  
Volumetric Flow Rate ◽  
Fluid Phase ◽  
Peristaltic Motion ◽  
Particle Volume ◽  
Two Phase ◽  
Peristaltic Pumping

This article addresses the influence of particulate-fluid suspension on asymmetric peristaltic motion through a curved configuration with mass and heat transfer. A motivation for the current study is that such kind of theory is helpful to examine the two-phase peristaltic motion between small muscles during the propagation of different biological fluids. Moreover, it is also essential in multiple applications of pumping fluid-solid mixtures by peristalsis, i.e., Chyme in small intestine and suspension of blood in arteriole. Long wavelength, as well as small Reynolds number, have been utilized to render the governing equations for particle and fluid phase. Exact solutions are presented for velocity (uf,p), temperature (θf,p) and concentration distributions (φf,p). All the parameters such as Prandtl number (Pr), particle volume fraction (C), suspension parameter (M1), curvature parameter (k), volumetric flow rate (Q), Schmidt number (Sc), phase difference (φ), Eckert number (Ec), and Soret number (Sr) discussed graphically for peristaltic pumping (Δp), pressure gradient (dp/dx), velocity (uf,p), temperature (θf,p) and concentration distributions (φf,p). The streamlines are also plotted with the aid of contour.

scholarly journals Development of Bubble Size Correlation for Adiabatic Forced Convective Bubbly Flow in Low Pressure Condition Using CFD Code

2020 ◽  
Vol 10 (16) ◽  
pp. 5443
Author(s):  
Jinyeong Bak ◽  
Huiyung Kim ◽  
Jae Jun Jeong ◽  
Dongjin Euh ◽  
Byongjo Yun
Keyword(s):  
Bubble Size ◽  
Bubbly Flow ◽  
Flow Analysis ◽  
Low Pressure ◽  
Good Prediction ◽  
Two Phase ◽  
Local Bubble ◽  
Computational Fluid Dynamics Cfd ◽  
Bubble Number ◽  
Bubble Number Density

In a multidimensional two-phase flow analysis, bubble size significantly affects interfacial transfer terms such as mass, momentum, and energy. With regard to bubbly flow, the application of a simple correlation-type bubble size model presents certain advantages, including short calculation times and ease of usage. In this study, we propose a semi-theoretical correlation developed from a steady state bubble number density transport equation for predicting the distribution of local bubble size using a computational fluid dynamics (CFD) code. The coefficients of the new correlation were determined using the local bubble parameters obtained on the basis of three existing vertical air-water experiments. Finally, these were implemented in commercial CFD code and evaluated against experimental data, which showed that the proposed correlation exhibits good prediction capability for forced convective air-water bubbly flows under low pressure conditions.

Vortex Simulation for Behavior of Solid Particles Falling in Air

2011 ◽  
Author(s):  
Hisanori Yagami ◽  
Tomomi Uchiyama
Keyword(s):  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Air Flow ◽  
Three Dimensional ◽  
Particle Diameter ◽  
Vortex Method ◽  
Solid Particles ◽  
Particle Volume ◽  
Two Phase ◽  
Spherical Region

The behavior of small solid particles falling in an unbounded air is simulated. The particles, initially arranged within a spherical region in a quiescent air, are made to fall, and their fall induces the air flow around them, resulting in the gas-particle two-phase flow. The particle diameter and density are 1 mm and 7.7 kg/m3 respectively. A three-dimensional vortex method proposed by one of the authors is applied. The simulation demonstrates that the particles are accelerated by the induced downward air flow just after the commencement of their fall. It also highlights that the particles are whirled up by a vortex ring produced around the downward air flow after the acceleration. The effect of the particle volume fraction at the commencement of the fall is also explored.

Development of Prediction Technology of Two-Phase Flow Dynamics Under Earthquake Acceleration: (12) Bubble Motion Along the Flow in Structure Vibration

2014 ◽  
Author(s):  
Yuki Kato ◽  
Rie Arai ◽  
Akiko Kaneko ◽  
Hideaki Monji ◽  
Yutaka Abe ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Velocity Field ◽  
Test Section ◽  
Two Phase Flow ◽  
Flow Behavior ◽  
Bubbly Flow ◽  
Experimental Results ◽  
Phase Flow ◽  
Bubble Motion ◽  
Two Phase

In a nuclear power plant, one of the important issues is an evaluation of the safety of the 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 is 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 and/or the power of core are fluctuated with the oscillation by the experiments and numerical analysis. However the 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 behavior. In order to investigate the influence of vibration of construction on bubbly flow behavior, we visualized bubbly flow in pipeline on which sine wave was applied. In a test section, bubbly flow was produced by injecting gas into liquid flow through a horizontal circular pipe. In order to vibrate the test section, an oscillating table was used. The frequency and acceleration of vibration added from the oscillating table was from 1.0 Hz to 10 Hz and . 0.4 G (1 G=9.8 m/s2) at each frequency. The test section and a high speed video camera were fixed on the oscillating table. Thus the relative velocity between the camera and the test section was ignored. PIV measurement was also conducted to investigate interaction between bubble motion and surround in flow structure. Liquid pressure was also measured at upstream and downstream of the test section. The effects of oscillation on bubbly flow were quantitatively evaluated by these pressure measurements and the velocity field. In the results, it was observed that the difference of bubble motion by changing oscillation frequency. Moreover it was suggested that the bubble deformation is correlated with the fluctuation of liquid velocity field around the bubble and the pressure gradient in the flow area. In addition, these experimental results were compared with numerical simulation by a detailed two-phase flow simulation code with an advanced interface tracking method, TPFIT. Numerical simulation was qualitatively agreed with experimental results.

Liquid Turbulence Spectra in Two-Phase Bubbly Flow Under Turbulence Augmentation and Suppression Conditions

2006 ◽  
Author(s):  
Mohamed E. Shawkat ◽  
Chan Y. Ching ◽  
Mamdouh Shoukri
Keyword(s):  
Void Fraction ◽  
Bubbly Flow ◽  
Bubble Diameter ◽  
Optical Probe ◽  
Wave Number ◽  
Two Phase ◽  
Number Range ◽  
Turbulence Spectra ◽  
Turbulence Suppression ◽  
Wave Number Range

An experimental investigation was performed in air-water bubbly flow to study the liquid turbulence spectra in a 200mm diameter vertical pipe. A dual optical probe was used to measure the local void fraction and bubble diameter while the liquid velocities were measured using hot-film anemometry. Experiments were performed at two liquid superficial velocities of 0.2 and 0.68m/s for gas superficial velocities in the range of 0 to 0.18m/s. Generally, as the void fraction increases there is a turbulence augmentation. However, a turbulence suppression was observed near the pipe wall at the higher liquid flow rate for low void fraction. In the augmentation case, the turbulence spectra showed a significant increase in the energy at the wave number range comparable to the bubble diameter. In the suppression case, the spectra showed that suppression initially occurs at the low wave number range and then extends to higher wave numbers as suppression increased.

scholarly journals Wake attenuation in large Reynolds number dispersed two-phase flows

2008 ◽  
Vol 366 (1873) ◽  
pp. 2177-2190 ◽  
Author(s):  
Frédéric Risso ◽  
Véronique Roig ◽  
Zouhir Amoura ◽  
Guillaume Riboux ◽  
Anne-Marie Billet
Keyword(s):  
Reynolds Number ◽  
Volume Fraction ◽  
Bubble Diameter ◽  
Temporal Variations ◽  
The Body ◽  
Experimental Investigations ◽  
Large Reynolds Number ◽  
Two Phase Flows ◽  
Two Phase ◽  
Multi Body

The dynamics of high Reynolds number-dispersed two-phase flow strongly depends on the wakes generated behind the moving bodies that constitute the dispersed phase. The length of these wakes is considerably reduced compared with those developing behind isolated bodies. In this paper, this wake attenuation is studied from several complementary experimental investigations with the aim of determining how it depends on the body Reynolds number and the volume fraction α . It is first shown that the wakes inside a homogeneous swarm of rising bubbles decay exponentially with a characteristic length that scales as the ratio of the bubble diameter d to the drag coefficient C d , and surprisingly does not depend on α for 10 −2 ≤ α ≤10 −1 . The attenuation of the wakes in a fixed array of spheres randomly distributed in space ( α =2×10 −2 ) is observed to be stronger than that of the wake of an isolated sphere in a turbulent incident flow, but similar to that of bubbles within a homogeneous swarm. It thus appears that the wakes in dispersed two-phase flows are controlled by multi-body interactions, which cause a much faster decay than turbulent fluctuations having the same energy and integral length scale. Decomposition of velocity fluctuations into a contribution related to temporal variations and that associated to the random character of the body positions is proposed as a perspective for studying the mechanisms responsible for multi-body interactions.

Two-Phase Stirring Flow Analysis of the Ruston Turbine in Stirred Tank

2014 ◽  
Vol 1008-1009 ◽  
pp. 979-982
Author(s):  
Xiao Bing Wang
Keyword(s):  
Volume Fraction ◽  
Flow Analysis ◽  
Stirred Tank ◽  
Low Density ◽  
Two Phase ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Tank Bottom ◽  
Close Distance ◽  
Turbine Installation

The effect of the turbine installation position on two-phase flow of a single six-blade ruston turbine in stirred tank with different agitation speeds is numerically simulated by using the large eddy simulation combined with mixture model. The result shows that when stirring low-density mixture, with the increasing stirring axle speed, volume fraction of low-density granules near the paddle is higher, while that near the barrel is low. When the paddle is installed with close distance to the tank bottom, the upper low-density granules are transported to the tank bottom to form good stirring effect. With increasing of the paddle location, distribution of low-density granules is hardly found at the bottom of stirred tank.

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