scholarly journals Experimental and Numerical Investigation of Bubble–Bubble Interactions during the Process of Free Ascension

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1977 ◽  
Author(s):  
Huang Ying ◽  
Gao Puzhen ◽  
Wang Chaoqun
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Momentum Equation ◽  
Velocity Variation ◽  
High Speed Photography ◽  
Movement Trajectory ◽  
Bubble Interactions ◽  
Cyclical Process ◽  
Velocity Changes ◽  
Two Bubbles

The shape and rising behavior of the horizontally arranged twin bubbles in a steady liquid are experimentally studied employing high-speed photography and digital image processing, and numerically studied by the Volume-Of-Fluid (VOF) method, in combination with a momentum equation coupled with a surface tension model. The movement trajectory and the velocity variation in horizontal and vertical directions of the horizontally arranged twin bubbles rising side by side, as observed in experiments, are described. According to the results, when two bubbles rise side by side, their horizontal velocity changes by the simple harmonic law; there is a cyclical process of two bubbles repeatedly attracted to and bounced against each other, rather than at constant distance between each other, and the bubbles swing up and down periodically in the water. The mathematical model and its numerical implementation are presented in detail. The validation of the model is confirmed by comparing the numerical and experimental results, which are in good agreement with each other; the numerical simulation can accurately reproduce the deformation, attraction, and repulsion of the bubble pairs. The phenomenon of attraction and repulsion is comprehensively analyzed from the viewpoint of a flow field. It is considered that the interaction between the bubbles is mainly influenced by the changes of the flow field due to vortex counteraction and wake merging effects.

Investigation of Particle Flow Field in Pyrotechnic Flame Based on Particle Image and Particle Velocity

2014 ◽  
Vol 962-965 ◽  
pp. 2789-2796
Author(s):  
Rui Xue ◽  
Hou Qian Xu
Keyword(s):  
Flow Field ◽  
Particle Velocity ◽  
High Speed ◽  
Particle Image ◽  
Velocity Variation ◽  
Movement Trajectory ◽  
High Speed Video ◽  
Velocity Flow ◽  
Approximate Distribution ◽  
The Mathematical Model

Study on burning particles in flame can help us to grasp the pyrotechnic decomposition mechanism. The high speed video (HSV) and particle image velocity (PIV) were used in this paper to analyze the flow field consist of high temperature burning particles during pyrotechnic combustion. The binary image was obtained through grayscale treatment and adaptive threshold segmentation from HSV and PIV data, by which the coordinate of each particle was marked. On the basis, the movement trajectory of each particle during combustion was pursued by the most recent guidelines algorithm of cancroids matching. Through the method proposed in this study, the velocity variation of each particle was obtained, the approximate distribution of particle quantity at each zone was visualized and the mathematical model of pyrotechnic particle velocity flow field was established.

The Application of PIV in the Study of Impeller-Diffuser Interaction in Centrifugal Fan: Part I — Impeller-Vaneless Diffuser Interaction

2001 ◽  
Author(s):  
Tarek Mekhail ◽  
Zhang Li ◽  
Du Zhaohui ◽  
Willem Jansen ◽  
Chen Hanping
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
High Speed ◽  
Maximum Flow ◽  
Image Processing Technique ◽  
High Speed Photography ◽  
Centrifugal Fan ◽  
Performance Measurements ◽  
Vaneless Diffuser ◽  
Unstable Flow

Abstract The PIV (Particle Image Velocimetry) technology is a brand-new technique of measuring velocity. It started in the 1980’s with the development of high-speed photography and the image processing technique of computers. This article deals with PIV applied to the study of unsteady impeller-vaneless diffuser interaction in centrifugal fen. Experiments were carried out at The Turbomachinery Laboratory of Shanghai Jiaotong University. The test rig consists of a centrifugal, shrouded impeller, diffuser and volute casing all made of plexiglass. A series of performance measurements were carried out at different speeds and different vaneless diffuser widths. PIV measurements were applied to measure the unsteady flow at the exit part of the impeller and the inlet part of the diffuser for the case of the same width vaneless diffuser. The absolute flow field is measured at medium flow rate and at maximum flow rate. It is informative to capture the whole flow field at the same instant of time, and it might be more revealing to observe the unstable flow in real time.

INTERACTION OF TWO DIFFERENTLY SIZED BUBBLES IN A FREE FIELD

2012 ◽  
Vol 19 ◽  
pp. 180-184
Author(s):  
LUP WAI CHEW ◽  
BOO CHEONG KHOO ◽  
EVERT KLASEBOER ◽  
SIEW-WAN OHL
Keyword(s):  
High Speed ◽  
Free Field ◽  
Real Life ◽  
Separation Distance ◽  
Liquid Jets ◽  
Size Difference ◽  
High Speed Photography ◽  
Distinct Region ◽  
Bubble Interactions ◽  
Multiple Bubbles

The interaction between two different sized (spark created, non-equilibrium) bubbles is studied by using high speed photography. The bubble size ranges from 2 to 7 mm. The experimental results are compared to that of the similar sized bubbles reported in the literature. Interestingly, all the four major behaviors of bubble-bubble interactions (i.e. 'bubble-collapsed' induced liquid jets directed away from each other, liquid jets directed towards each other, bubble coalescence and the 'catapult' effect) are observed which bear much similarity to that found for similar sized bubbles' interaction. The main parameters studied/varied are the size of the bubbles, the dimensionless separation distance and the phase difference between the two bubbles. The results obtained are consistent with the cases of similar sized bubbles reported in the literature, with each type of behavior occupying a distinct region in the graphical plot. This indicates that the results for the (special) similar sized bubbles can be generalized to cases with different sized bubbles. Many of the real life applications such as cavitations corrosions often involve bubbles with significant size difference, thus the present findings are useful in predicting the behavior of multiple bubbles in many situations.

MULTIPLE SPARK-GENERATED BUBBLE INTERACTIONS

2009 ◽  
Vol 23 (03) ◽  
pp. 229-232 ◽  
Author(s):  
BOO CHEONG KHOO ◽  
DEEPAK ADIKHARI ◽  
SIEW WAN FONG ◽  
EVERT KLASEBOER
Keyword(s):  
High Speed ◽  
Bubble Surface ◽  
Solid Boundary ◽  
High Speed Photography ◽  
Bubble Interactions ◽  
Complex Interactions ◽  
Bubble Splitting ◽  
Shape Changes ◽  
Insight Into ◽  
Phase Differences

The complex interactions of two and three spark-generated bubbles are studied using high speed photography. The corresponding simulations are performed using a 3D Boundary Element Method (BEM) code. The bubbles generated are between 3 to 5 mm in radius, and they are either in-phase or out-of-phase with one another. The possible interaction phenomena between two identically sized bubbles are summarized. Depending on their relative distances and phase differences, they can coalesce, jet towards or away from one another, split into smaller bubbles, or 'catapult' away from one another. The 'catapult' effect can be utilized to generated high speed jet in the absence of a solid boundary or shockwave. Also three bubble interactions are highlighted. Complicated phenomena such as bubble forming an elliptical shape and bubble splitting are observed. The BEM simulations provide insight into the physics of the phenomena by providing details such as detailed bubble shape changes (experimental observations are limited by the temporal and spatial resolution), and jet velocity. It is noted that the well-tested BEM code [1,2] utilized here is computationally very efficient as compared to other full-domain methods since only the bubble surface is meshed.

scholarly journals Synthetic jet generation by high-frequency cavitation

2017 ◽  
Vol 823 ◽  
Author(s):  
Milad Mohammadzadeh ◽  
Silvestre Roberto Gonzalez-Avila ◽  
Kun Liu ◽  
Qi Jie Wang ◽  
Claus-Dieter Ohl
Keyword(s):  
High Frequency ◽  
Laser Power ◽  
High Speed ◽  
Bubble Formation ◽  
Acoustic Streaming ◽  
High Repetition Rate ◽  
Synthetic Jet ◽  
Bubble Collapse ◽  
High Speed Photography ◽  
Bubble Interactions

Cavitation bubbles are nucleated at a high repetition rate in water by delivering a pulsed laser through a fibre optic. Continuous high-frequency cavitation drives a stream away from the fibre tip. Using high-speed photography and particle image velocimetry, the stream is characterised as a synthetic jet, generated by trains of vortices induced by non-spherical bubble collapse. At low laser power, the bubbles collapse before the arrival of a subsequent laser pulse. Yet, by increasing the laser power, a system of bubbles is formed which leads to complex bubble–bubble interactions. The synthetic jet is observed regardless of the bubble formation regime, demonstrating the stability of the phenomenon. Synthetic jet generation by repetitive bubble collapse extends the well-studied acoustic streaming from small-amplitude bubble oscillations.

Crack divergence phenomena in tempered glass

2020 ◽  
Vol 13 (3) ◽  
pp. 115-129
Author(s):  
Shin’ichi Aratani
Keyword(s):  
Optimal Design ◽  
High Speed ◽  
Glass Plate ◽  
Acute Angle ◽  
Divergence Angle ◽  
High Speed Photography ◽  
Tempered Glass ◽  
Thick Glass

High speed photography using the Cranz-Schardin camera was performed to study the crack divergence and divergence angle in thermally tempered glass. A tempered 3.5 mm thick glass plate was used as a specimen. It was shown that two types of bifurcation and branching existed as the crack divergence. The divergence angle was smaller than the value calculated from the principle of optimal design and showed an acute angle.

Experimental study of hydrodynamic effects in the inverse water hydrocarbon emulsions flow in microchannels

2016 ◽  
Vol 11 (1) ◽  
pp. 30-37 ◽  
Author(s):  
A.A. Rakhimov ◽  
A.T. Akhmetov
Keyword(s):  
High Speed ◽  
Petroleum Industry ◽  
Chemical Compounds ◽  
High Viscosity ◽  
Blocking Effect ◽  
High Speed Photography ◽  
Simple Chemical ◽  
Reported Study ◽  
Dynamic Blocking ◽  
Hydrodynamic Effects

The paper presents results of hydrodynamic and rheological studies of the inverse water hydrocarbon emulsions. The success of the application of invert emulsions in the petroleum industry due, along with the high viscosity of the emulsion, greatly exceeding the viscosity of the carrier phase, the dynamic blocking effect, which consists in the fact that the rate of flow of emulsions in capillary structures and cracks falls with time to 3-4 orders, despite the permanent pressure drop. The reported study shows an increase in viscosity with increasing concentration or dispersion of emulsion. The increase in dispersion of w/o emulsion leads to an acceleration of the onset of dynamic blocking. The use of microfluidic devices, is made by soft photolithography, along with high-speed photography (10,000 frames/s), allowed us to see in the blocking condition the deformation of the microdroplets of water in inverse emulsion prepared from simple chemical compounds.

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