216 PIV measurement of circumferential flow structure of Taylor column

Various methods of controlling flow separation have been proposed and many studies have been performed on active separation control in correspondence with the flow state. However, their efficiency has been hampered by the requirement of electric power for the added stream. Recently, an active flow separation control device based on a fluidic oscillator that does not require electric power has been reported. This device is able to generate a sweeping jet over a wide spatial range as well as fluid oscillations, and its internal structure eliminates the need for a drive unit. The studies of the flow separation control techniques using the fluidic oscillator have been reported. However, most of these results are mainly contribution of the dynamic forces from the viewpoint of the flow control and the study on the flow mechanism for the separation flow control using the fluidic oscillator have not been understood. Especially, it is not known the interaction between the sweeping jet from the fluidic oscillator and the main flow and the flow structure due to the interaction. In order to make a flow separation control devise with high efficiency using the fluidic oscillator, it is require to be understood the complex flow structure by the interaction between the sweeping jet from the fluidic oscillator and the main flow. The purpose of the present study is to investigate the flow structure by the interaction between the sweeping jet from the fluidic oscillator and the main flow quantitatively by the stereo PIV measurement. The sweeping jet ejected from a fluidic oscillator evidently disrupts the main flow at high velocity ratios, leading to a significant change in flow structure. A high-speed jet appears at the center part of the structure, accompanied by low-speed flow at the outside, producing a 3D distribution. The sweeping jet ejected from the fluidic oscillator maintains the spreading angleas a result of the interaction between the two flows at high velocity ratios.

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

Volume 3: Thermal-Hydraulics; Turbines, Generators, and Auxiliaries ◽

10.1115/icone20-power2012-54602 ◽

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.

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Investigation of Micro Droplet Formation in a T-Shaped Junction Using Multicolor Confocal Micro PIV

ASME 2008 First International Conference on Micro/Nanoscale Heat Transfer, Parts A and B ◽

10.1115/mnht2008-52365 ◽

2008 ◽

Cited By ~ 3

Author(s):

Masamichi Oishi ◽

Haruyuki Kinoshita ◽

Marie Oshima ◽

Teruo Fujii

Keyword(s):

Multiphase Flow ◽

Flow Structure ◽

Dynamical Behavior ◽

Internal Flow ◽

Droplet Formation ◽

Immiscible Fluids ◽

Present System ◽

Micro Particle Image Velocimetry ◽

Micro Piv ◽

Piv Measurement

This paper aims to investigate a mechanism of microdroplet formation using “multicolor confocal micro particle image velocimetry (PIV)” technique. The present system can measure dynamical behavior of multiphase flow separately and simultaneously. It also enables to identify the interactions between two immiscible fluids. We have applied this system to measure the water droplet formation at a micro T-shaped junction. We have also succeeded in dispersing fluorescent tracer particles into both phases. The interaction between the internal flow of to-be-dispersed water phase and of continuous oil phase is measured as a liquid-liquid multiphase flow. As a result of PIV measurement and interfacial geometry scanning, the relationship between flow structure of each fluid and interfacial geometry is clarified. It indicates that the gap between the tip of discontinuous flow and capillary wall, and interface area play an important role in the flow structure and shear stress on the interface.

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Research on Flow Field of a Fixed Duct in a Rotary Energy Recovery Device

Volume 1B, Symposia: Fluid Measurement and Instrumentation; Fluid Dynamics of Wind Energy; Renewable and Sustainable Energy Conversion; Energy and Process Engineering; Microfluidics and Nanofluidics; Development and Applications in Computational Fluid Dynamics; DNS/LES and Hybrid RANS/LES Methods ◽

10.1115/fedsm2017-69087 ◽

2017 ◽

Cited By ~ 1

Author(s):

K. Liu ◽

J. Q. Deng ◽

B. Yang

Keyword(s):

Flow Field ◽

Flow Structure ◽

Energy Recovery ◽

Flow Instability ◽

Structural Parameters ◽

Operating Conditions ◽

Small Scale ◽

Mixing Rate ◽

Piv Measurement ◽

Turbulent Flow Structure

An experimental study was carried out to investigate flow structures in the duct of a rotary energy recovery device (RERD). In order to visualize the flow field, a new type structure of the RERD was proposed in this experiment, which had a fixed duct and two rotating ports. A two-dimensional particle image velocimetry (PIV) measurement was performed to visualize the flow structure in the duct of the RERD. The turbulent flow structure in the duct was analyzed. The instantaneous vorticity contours and associated vectors showed the generation of vorticities in the duct. Moreover, the formation of the small-scale-vortex would significantly increase the flow instability and the fluid mixing rate. These results may be beneficial to researchers in better understanding the flow dynamic in the duct of a RERD and optimize the operating conditions and structural parameters of it.

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Flow Structure behind a Wing at High Reynolds Numbers

EPJ Web of Conferences ◽

10.1051/epjconf/201818002111 ◽

2018 ◽

Vol 180 ◽

pp. 02111 ◽

Cited By ~ 2

Author(s):

Václav Uruba ◽

Zdeněk Pátek ◽

Pavel Procházka ◽

Vladislav Skála ◽

David Zacho ◽

...

Keyword(s):

Wind Tunnel ◽

Flow Structure ◽

Reynolds Numbers ◽

Streamwise Direction ◽

Vortical Structures ◽

High Reynolds Numbers ◽

Piv Measurement ◽

High Reynolds

The stereo PIV measurement were performed behind a wing in the plane perpendicular to the flow to study the vortical structures oriented in the streamwise direction, which take place both in suction and pressure sides of the wing. The Reynolds numbers during the experiments in the 3 m wind tunnel range from 0.5 million up to 1.5 million.

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Development of Prediction Technology of Two-Phase Flow Dynamics Under Earthquake Acceleration: 8 — Measurement of Velocity Profile Around Bubble Under Structure Vibration

Volume 4: Thermal Hydraulics ◽

10.1115/icone21-15569 ◽

2013 ◽

Author(s):

Kousuke Mizuno ◽

Rie Arai ◽

Akiko Kaneko ◽

Hideaki Monji ◽

Yutaka Abe ◽

...

Keyword(s):

Velocity Profile ◽

Flow Structure ◽

Test Section ◽

High Speed ◽

Liquid Velocity ◽

Bubbly Flow ◽

Oscillation Amplitude ◽

Bubble Deformation ◽

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 characteristic bubble deformation and velocity profile around bubble is caused by oscillation in each oscillation phase time. 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 the bubble deformation is correlated with the fluctuation of relative liquid velocity field to bubble and pressure gradient in the flow area.

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