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.

Drag Reduction of Gas-Liquid Two-Phase Flow in Steel Pipes with Different Inclination Geometry

2012 ◽  
Vol 433-440 ◽  
pp. 463-470
Author(s):  
Lei Liu ◽  
Xin Feng Guo ◽  
Qiu Yue Guo ◽  
Hui Qing Fan ◽  
Zhu Hai Zhong
Keyword(s):  
Drag Reduction ◽  
Two Phase Flow ◽  
Vertical Section ◽  
High Energy ◽  
Phase Flow ◽  
Two Phase ◽  
Steel Pipes ◽  
Horizontal Pipes ◽  
Reduction Efficiency ◽  
Reduction Characteristics

It is significant to make researches on drag reduction in two-phase transport pipeline because two-phase flow has high energy dissipation. API X 52 steel pipe with diameter of 40mm is used in this paper to simulate pipeline with different inclination geometry including horizontal, up-inclined and vertical sections. The up-inclined section has an inclination angle of eight degree. Experiments and theoretical analysis are carried out to study the drag reduction characteristics of gas-liquid two-phase flow in these three sections. The drag reducing agents used here is polyacrylamide. It is found that two-phase drag reduction varies with pipe inclination geometry. The largest drag reduction efficiency occurs in horizontal pipes and which is up to seventy percent. Drag reduction efficiency in up-inclined section is up to sixty percent. Drag reduction in vertical section is the lowest and which can be up to about thirty percent. A mechanistic drag reduction model is proposed to predict drag reduction in gas-liquid two-phase flow. The results predicted are in good agreement with the experiment data.

Hydrodynamics of gas/shear-thinning liquid two-phase flow in a co-flow mini-channel: Flow pattern and bubble length

2020 ◽  
Vol 32 (9) ◽  
pp. 092004
Author(s):  
Wen Yuan Fan ◽  
Shuai Chao Li ◽  
Li Xiang Li ◽  
Xi Zhang ◽  
Meng Qi Du ◽  
...  
Keyword(s):  
Flow Pattern ◽  
Channel Flow ◽  
Two Phase Flow ◽  
Shear Thinning ◽  
Phase Flow ◽  
Two Phase ◽  
Bubble Length

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.

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.

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