scholarly journals Development of PIV measurement technique in turbulent flow laden with binary-size particle groups

2020 ◽  
Vol 37 ◽  
pp. 161-171
Author(s):  
Wei-Cheng Chen ◽  
Keh-Chin Chang
Keyword(s):  
Spatial Information ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Phase Discrimination ◽  
Piv Measurement ◽  
Mean Size ◽  
Field Measuring ◽  
The Mean ◽  
Binary Group

Abstract Particle image velocimetry (PIV) is an instantaneous whole-field measuring diagnostic that makes it feasible to measure the microscale spatial information of the interphase dynamics for good understanding of two-phase flow. However, application of PIV to the two-phase flow measurement is still a state of the art so far. A double-discriminating process in terms of gray level and size of image patterns together with the median mask technique is developed. The test flow is a turbulent air wake laden with a binary group of particles with the mean size of 2.7 μm (representing the carrier phase) and 55 μm (representing the dispersed phase). It is demonstrated that the velocity measurements of both phases can be successfully performed through the combined PIV/PTV (particle tracking velocimetry) scheme associated with the developed phase discrimination method. It is noted that the discriminating capability of the size ratio between the large- and small-particle groups in the study is around 20 together with the mean size of O(100 μm) for small particles, which is the commonly required size for the seedings used in the PIV measurements of airflows, as compared to the size of O(101  μm) adopted in the current two-phase PIV measurement methods.

Flow Characteristics of Adiabatic Gas-Liquid Two-Phase Flow in a Horizontal Flat Rectangular Microchannel

2011 ◽  
Author(s):  
Hideo Ide ◽  
Kentaro Satonaka ◽  
Tohru Fukano
Keyword(s):  
Void Fraction ◽  
Slug Flow ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Flow Characteristics ◽  
Flow Patterns ◽  
Phase Flow ◽  
Similar Data ◽  
Two Phase ◽  
The Mean

Experiments were performed to obtain, analyze and clarify the mean void fraction, the mean liquid holdup, and the liquid slug velocity and the air-water two-phase flow patterns in horizontal rectangular microchannels, with the dimensions equal to 1.0 mm width × 0.1 mm depth, and 1.0 mm width × 0.2 mm depth, respectively. The flow patterns such as bubble flow, slug flow and annular flow were observed. The microchannel data showed similar data patterns compared to those in minichannels with the width of 1∼10mm and the depth of 1mm which we had previously reported on. However, in a 1.0 × 0.1 mm microchannel, the mean holdup and the base film thickness in annular flow showed larger values because the effects of liquid viscosity and surface tension on the holdup and void fraction dominate. The remarkable flow characteristics of rivulet flow and the flow with a partial dry out of the channel inner wall were observed in slug flow and annular flow patterns in the microchannel of 0.1 mm depth.

Interaction Between Two Falling Droplets in the Liquid-Liquid Two Phase Flow

2011 ◽  
Author(s):  
Nao Ninomiya ◽  
Takeshi Mori
Keyword(s):  
Aqueous Solution ◽  
Multiphase Flow ◽  
Physical Mechanism ◽  
Two Phase Flow ◽  
Refractive Indices ◽  
Phase Flow ◽  
Two Phase ◽  
Piv Measurement ◽  
The Difference ◽  
Simultaneous Visualization

Although the phenomena related to the multiphase flow can be found in many kinds of industrial and engineering applications, the physical mechanism of the multiphase flow has not been investigated in detail. The major reason for the lack of data in the multiphase flow lies in the difficulties in measuring the flow quantities of the multiple phases simultaneously. The difference in the refractive indices makes the visualization in the vicinity of the boundary of the multiple phases almost impossible. In this study, the refractive index of the aqueous phase has been equalized to that of the oil phase by adjusting the concentration of aqueous solution. Presently, the simultaneous visualization and the PIV measurement have been carried out about the both phases of the liquid-liquid two-phase flow. The measurement has been carried out for the flow field around and inside of two falling droplets interacting each other while they travel.

Heat Transfer for Annular Flow in Microchannel Bends: A Free Energy Minimization Model for Square Channels

2007 ◽  
Author(s):  
Sara Beaini ◽  
Van P. Carey
Keyword(s):  
Heat Transfer ◽  
Free Energy ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Centrifugal Acceleration ◽  
Two Phase ◽  
The Mean ◽  
Flow Morphology ◽  
Liquid Vapor

For annular liquid-vapor two-phase flow in straight microchannels, effects of gravity are generally small compared to viscous and/or inertia forces. In serpentine evaporator or condenser passages with semicircular return bends, the bend radius may be so small that large centrifugal body forces are generated as the fluid flows through the bend region of the passage. This paper summarizes a model analysis based on the premise that flow morphology in the bend is dictated by radial acceleration forces and the thermodynamic Second Law requirement that the established two-phase flow morphology minimizes the free energy at the local temperature and pressure. An analytical model is derived relating the dependence of the free energy on vapor core geometry, and the geometry that minimizes free energy is determined numerically. This provides a prediction of the mean thickness of the liquid surrounding the vapor core, and the mean heat transfer coefficient for annular flow vaporization or condensation, as a function of flow parameters and physical properties. When this relation is cast in dimensionless form, the effect of centrifugal acceleration is quantified in terms of a Weber number (We) that represents the ratio of centrifugal body force to surface tension force. The analysis indicates that centrifugal acceleration acts to displace the vapor towards the inside of the curved passage and distort the liquid-vapor interface. Displacement occurs at any level of acceleration. Significant distortion is found to occur only for We > 1. The effects of these morphology changes on heat transfer are analyzed and the implications of these predictions for designing microchannel evaporators and condensers are explored.

Effect of Channel Length on the Gas-Liquid Two-Phase Flow Phenomena in a Microchannel

2009 ◽  
Author(s):  
Ryuji Kimura ◽  
Hideo Ide ◽  
Hiroshi Hashiguchi ◽  
Masahiro Kawaji
Keyword(s):  
Void Fraction ◽  
Test Section ◽  
Two Phase Flow ◽  
Optical Measurement ◽  
Liquid Velocity ◽  
Flow Characteristics ◽  
Phase Flow ◽  
Two Phase ◽  
Liquid Plug ◽  
The Mean

An optical measurement system was used to investigate the effect of microchannel length on adiabatic gas-liquid two-phase flow characteristics. Experiments were conducted with 146 mm and 1,571 mm long, circular microchannels of 100 micron diameter. Two-phase flow patterns, void fraction, gas and liquid plug lengths and their velocities were measured for two inlet configurations and gas-liquid mixing, i.e., (a) reducer and (b) T-junction. The test section length was found to have a significant effect on the two-phase flow characteristics measured at the same axial location in the microchannel test section typified by the void fraction data. The mean void fraction data obtained in the shorter (146 mm) microchannel with the reducer inlet agreed well with the equation by Kawahara and Kawaji which was previously proposed. On the other hand, the mean void fraction obtained at 36 mm from the inlet in the longer (1,571 mm) microchannel corresponded well with the homogeneous flow model and Armand’s equation for both reducer and T-junction inlet configurations. In the present experimental ranges of superficial gas velocity, jG = 0.03 ∼ 14 m/s, and superficial liquid velocity, jL = 0.04∼0.7 m/s, the gas and liquid plugs obtained in the longer microchannel had relatively shorter lengths and higher velocities than those in the shorter channel. Thus, both the microchannel length and inlet geometry were found to affect the two-phase flow characteristics in a microchannel.

Fluorescent Particle Injection Technique for Two-Phase Flow Measurement Using Particle Image Velocimetry

2006 ◽  
Author(s):  
Steven P. O’Halloran ◽  
B. Terry Beck ◽  
Mohammad H. Hosni ◽  
Steven J. Eckels
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Two Phase Flow ◽  
Phase System ◽  
Phase Flow ◽  
Two Phase ◽  
Particle Injection ◽  
Piv Measurement ◽  
Image Velocimetry ◽  
Fluorescent Particles

Particle image velocimetry (PIV) is a well established measurement technique to measure velocity in a variety of different fluids. Using PIV to measure single-phase flow is well established, but recently PIV has been used to measure two-phase flows as well. Most two-phase PIV measurements have been for dispersed or bubbly flows, often utilizing the bubbles or droplets as PIV seed particles. However, there are other types of two-phase flow situations, such as stratified or slug flow, in which PIV measurement techniques are not yet well established. Situations such as these require both liquid and gas phases to be seeded separately with particles that can distinguish each phase. A particle injection method is presented for the air phase of a two-phase system using fluorescent tracer particles. Information about the system, including details of the fluorescent particles and injection device are given. The device injects micron sized fluorescent particles at a uniform rate into the flow of interest. A cut-off lens filter on the PIV camera is used to distinguish the fluorescent particles used for the air phase from non-fluorescent particles used in the liquid phase. Results using the technique with a two-phase air/water system in a thin rectangular channel for stratified/wavy flow are given. The channel is enclosed in a clear acrylic plastic tank and the dimensions of the channel are 600 mm long, 40 mm high, and 15 mm wide. The results demonstrate the ability to use PIV to measure the gas phase of a two-phase system for stratified/wavy flow and the method could be extended to other two-phase flow regimes as well.

scholarly journals PIV measurement of particle motion in spiral gas–solid two-phase flow

1999 ◽  
Vol 19 (4) ◽  
pp. 194-203 ◽  
Author(s):  
Kaoru Miyazaki ◽  
Gang Chen ◽  
Fujio Yamamoto ◽  
Jun-ichi Ohta ◽  
Yuichi Murai ◽  
...  
Keyword(s):  
Particle Motion ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Piv Measurement

Wavelet Spatial Energy Spectrums Studies on Drag Reduction by Microbubble Injection

2006 ◽  
Author(s):  
Ling Zhen ◽  
Yassin A. Hassan
Keyword(s):  
Energy Spectrum ◽  
Drag Reduction ◽  
Channel Flow ◽  
Two Phase Flow ◽  
Turbulent Channel Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Wavelet Energy ◽  
Piv Measurement ◽  
Fluid Particles

In this study, continuous wavelet transforms and spatial correlation techniques are employed to determine the space-localized wavenumber energy spectrum of the velocity signals in turbulent channel flow. The flow conditions correspond to single phase flow and microbubbles injected two phase flow. The wavelet energy spectrums demonstrate that the wavenumber (eddy size) content of the velocity signals is not only space-dependent but also microbubbles can impact the eddy size content. Visual observations of the wavelet energy spectrum spatial distribution was realized by using Particle Image Velocimetry (PIV) measurement technique. The two phase flow condition corresponds to a drag reduction of 38.4% with void fraction of 4.9%. The present results provide evidence that microbubbles in the boundary layer of a turbulent channel flow can help adjust the eddy size distributions near the wall. This can assist in explaining that microbubbles are performing as buffers to keep the energy of fluid particles going in streamwise direction and reducing the energy of fluid particles going in normal direction.

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