Numerical Simulation of Microparticles Motion in Two-Phase Bubbly Flow

2021 ◽  
Author(s):  
Hiroyuki Yoshida ◽  
Shinichiro Uesawa
Keyword(s):  
Numerical Simulation ◽  
Bubbly Flow ◽  
Two Phase

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.

Fundamental Issues Related to the Numerical Simulation of Two-Phase Flows With Phase-Change

2006 ◽  
Author(s):  
Didier Jamet
Keyword(s):  
Numerical Simulation ◽  
Phase Change ◽  
Bubbly Flow ◽  
Nucleate Boiling ◽  
Phase System ◽  
High Heat Flux ◽  
Two Phase Flows ◽  
Miscible Fluids ◽  
Two Phase ◽  
Phase Change Phenomena

In direct numerical simulation (DNS) of two-phase flows, all the interfaces of the two-phase system are tracked individually. If this technique is computationally expensive, it is also very powerful, especially to study basic phenomena. In particular, it helped to better understand fundamental issues such as the forces acting on a single bubble (e.g. [1]) or the interaction of a couple of bubbles in a bubbly flow (e.g. [2,3]) and it now begins to be used to assess average models in detail ([4]). Currently, most of the basic phenomena studied involve non-miscible fluids, where no mass transfer between the phases occurs (air and water for instance). However, in many applications of industrial interest, phase-change phenomena are very important because high heat flux can be achieved with moderate temperature gradients (since the energy exchange through latent heat occurs at a constant temperature). It is thus widely used in the energy industry (nuclear energy in particular) and it is used to design compact heat exchangers (e.g. heat pipes for space or electronic devices). Moreover, basic phenomena related to phase-change are, to a large extent, still misunderstood, which make phase-change phenomena of fundamental interest as well. For instance, despite several decades of valuable scientific studies, the boiling crisis, which is an instability of the nucleate boiling regime, is still misunderstood from a fundamental point of view. It is one of the very few fundamental issues that are still open in fluid mechanics. Since DNS has already been successful to study fundamental issues in two-phase flows of non-miscible fluids, it should be successful to study these issues as well. However, the DNS of two-phase flows with phase-change is more difficult than that of two-phase flows involving non-miscible phases. These issues are both numerical and physical and some of them are discussed in this paper.

Development of Prediction Technology of Two-Phase Flow Dynamics Under Earthquake Acceleration: (14) Numerical Simulation of Two-Phase Flow in Subchannels Under Accelerating Condition

2014 ◽  
Author(s):  
Hiroyuki Yoshida ◽  
Taku Nagatake ◽  
Kazuyuki Takase ◽  
Akiko Kaneko ◽  
Hideaki Monji ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Nuclear Reactors ◽  
Bubbly Flow ◽  
Flow Simulation ◽  
Phase Flow ◽  
Two Phase ◽  
Void Fraction Distribution ◽  
Fraction Distribution

An earthquake is one of the most serious phenomena to consider for the safety of a nuclear reactor in Japan. Therefore, structural safety of nuclear reactors has been studied and nuclear reactors were contracting with structural safety for a big earthquake. However, it is not enough for safety operation of nuclear reactors because thermal-fluid safety is not confirmed under the earthquake. For instance, behavior of gas-liquid two-phase flow is unknown in seismic conditions. Especially, fluctuation of void fraction is an important factor for the safety operation of the nuclear reactor. In previous work, fluctuation of void faction in bubbly flow was studied experimentally and theoretically to investigate the stability of the bubbly flow. In such studies, flow rate or void fraction fluctuations were given to the steady bubbly flow. In case of the earthquake, the fluctuation is not only the flow rate, but also a body force on the two-phase flow and shear force through the pipe wall. Interactions of gas and liquid through their interface also act on the behavior of the two-phase flow. The fluctuation of the void fraction is not clear for such complicated situation during the earthquake. Therefore, the behavior of gas-liquid two-phase flow is investigated experimentally and numerically in a series of studies. In this study, to develop the predictive technology of two-phase flow dynamics under earthquake acceleration, a detailed two-phase flow simulation code with an advanced interface tracking method TPFIT (Two-Phase Flow simulation code with Interface Tracking) was expanded to two-phase flow simulation in seismic conditions. In a previous study, we performed a numerical simulation of a two-phase bubbly flow in a horizontal pipe and a vertical bubble motion in a water tank in seismic conditions. And it was confirmed that the modified TPFIT can be applicable to the bubbly flow in seismic conditions. In this paper, the two-phase bubbly flow in a simulated single-subchannel excited by oscillation acceleration was simulated by using the expanded TPFIT. A calculation domain used in this simulation was a simplified subchannel in a BWR core. And time-series of void fraction distributions were evaluated based on predicted bubble distributions. When no oscillation acceleration was added, void fraction concentrated in a region near the wall. When oscillation acceleration was added, void fraction distribution was changed by time. And coalesces of bubbles occurred in the numerical simulation, and bubbles with relatively large diameter were observed. In the results, complicated void fraction distribution was observed, because the response of void fraction distribution on the oscillation acceleration was dependent on not only imposed acceleration, but also the bubble diameter.

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.

scholarly journals Using a Dynamic and Constant Mesh in Numerical Simulation of the Free-Rising Bubble

Fluids ◽  
2019 ◽  
Vol 4 (1) ◽  
pp. 38 ◽  
Author(s):  
Zlatko Rek
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Computational Fluid Dynamics ◽  
Bubbly Flow ◽  
Process Industry ◽  
Computational Grids ◽  
Two Phase ◽  
Efficient Operation ◽  
Rising Bubble ◽  
Computational Fluid Dynamics Cfd

A two-phase bubbly flow is often found in the process industry. For the efficient operation of such devices, it is important to know the details of the flow. The paper presents a numerical simulation of the rising bubble in a stagnant liquid column. The interFOAM solver from the open source Computational Fluid Dynamics (CFD) toolbox OpenFOAM was used to obtain the necessary data. The constant and dynamic computational grids were used in the numerical simulation. The results of the calculation were compared with the measured values. As expected, by using the dynamic mesh, the bubble trajectory was closer to the experimental results due to the more detailed description of the gas–liquid interface.

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