scholarly journals Measurement of Bubble Dynamics by an Optical Fiber Probe. 2nd Report. Simultaneous Measurement of Interfacial Velocity and Chord Length of a Bubble.

2002 ◽  
Vol 68 (674) ◽  
pp. 2719-2726 ◽  
Author(s):  
Takayuki SAITO ◽  
Takeo KAJISHIMA
Keyword(s):  
Optical Fiber ◽  
Simultaneous Measurement ◽  
Bubble Dynamics ◽  
Chord Length ◽  
Interfacial Velocity ◽  
Fiber Probe ◽  
Optical Fiber Probe

A Newly Developed Technique for Detection of a Contact Position in Bubble Measurements by a Single-Tip Optical Fiber Probe

2011 ◽  
Author(s):  
Yuki Mizushima ◽  
Takayuki Saito
Keyword(s):  
Optical Fiber ◽  
Wedge Angle ◽  
Outer Edge ◽  
Chord Length ◽  
Two Phase ◽  
Frontal Surface ◽  
Fiber Probe ◽  
Optical Fiber Probe ◽  
Contact Position ◽  
The Relationship

An optical fiber probe has been frequently employed to measure bubble diameters, velocities, and local void fractions simultaneously in gas-liquid two-phase systems. For the application of the probe to tiny-bubble measurement, one of the authors already developed a Single-Tip Optical fiber Probe (STOP). The purpose of this study is to rapidly improve the measurement accuracy of the S-TOP. A bubble chord length pierced by the S-TOP is obtained. Consequently, the chord length depends on the pierced position. The chord lengths measured by the S-TOP include an error owing to the random positions pierced by the S-TOP; i.e. the measured chord length becomes shorter than the bubble minor axis, with a shift of the contact position towards the outer edge of the bubble. The S-TOP axis crosses the direction of the bubble motion at a random angle. This also causes a miscalculation of the chord lengths. In order to correct these errors in the S-TOP measurement, we need to detect the contact position and the intersection angles. To realize this, using a pre-signal is quite effective. The pre-signal is generated clearly and intensively, only when the S-TOP sensing tip is ground in a wedge shape and the tip touches vertically the center region of the bubble frontal surface. The pre-signal becomes weak and indistinct under the other contact conditions. Making the smart use of these phenomena, we are able to solve the above defects of the S-TOP. First, the relationship between the intensity of the pre-signal and the pierced positions/angles is systematically quantified. Second, a signal processing to detect the pierced positions/angles, based on the relationship, is established. Third, we discuss a mechanism of the pre-signal. We determine the most suitable S-TOP size, tip diameter and wedge-angle, for the most accurate measurement. Finally, we demonstrate the effectiveness of our newly proposed method.

Effect of L/D Ratio on Phase Holdup and Bubble Dynamics in Slurry Bubble Column using Optical Fiber Probe Measurements

2016 ◽  
Vol 14 (2) ◽  
pp. 653-664 ◽  
Author(s):  
Saba A. Gheni ◽  
Yasser I. Abdulaziz ◽  
Muthanna H. Al-Dahhan
Keyword(s):  
Optical Fiber ◽  
Bubble Dynamics ◽  
Bubble Column ◽  
Gas Holdup ◽  
Solid Loading ◽  
Gas Velocity ◽  
Fiber Probe ◽  
Optical Fiber Probe ◽  
Slurry Bubble Column ◽  
Superficial Gas Velocity

Abstract In this investigation, time average local gas holdup and bubble dynamic data were achieved for three L/D ratios of slurry bubble column. The examined ratios were 3, 4 and 5 in 18″ diameter slurry bubble column. Air-water-glass bead system was used with superficial gas velocity up to 0.24 m/s. The gas holdup was measured using four tips optical fiber probe technique. The results showed that the gas holdup increases almost linearly with the superficial gas velocity in 0.08 m/s and levels off with a further increase of velocity. A comparison of the present data with those reported for other slurry bubble column having diameters greater than 18″ and L/D higher than 5 was made. The results indicated a little effect of diameter on the gas holdup. A local, section-averaged gas holdup increases with increasing superficial gas velocity, while the effect of solid loading are less significant than that of the superficial gas velocity. Chaos analysis was used to analyze the slurry system.

Evaluation of the Influences of Surface Tension on the Bubble Measurement Using a Single-Tip Optical Fiber Probe

2007 ◽  
Author(s):  
Yusuke Ozawa ◽  
Takayuki Saito
Keyword(s):  
Surface Tension ◽  
Optical Fiber ◽  
Simultaneous Measurement ◽  
Leading Edge ◽  
Optical Probe ◽  
Surface Wettability ◽  
Fiber Probe ◽  
Probe Surface ◽  
Optical Fiber Probe ◽  
Bubble Measurement

The optical probe method has been repeatedly improved in order to measure bubbles and droplets efficiently and reliably in gas-liquid two-phase flows, since the application of an optical fiber to measure them was proposed early eighties. However, simultaneous measurement of their diameters and velocities has been thought to need at least two optical fiber probes. To break through this situation, we newly developed a Single-Tip Optical fiber Probe (S-TOP) which realizes simultaneous measurement of diameters and velocities of minute bubbles/droplets. In the S-TOP measurement, the relation between the reflected-light intensity at the wedge-shaped probe tip and the tip-surface area covered with a phase is cleverly used to realize the simultaneous measurement. The surface tension and probe-surface wettability intensively influence the S-TOP signals. The main aim of the present study is to strictly evaluate the influences of surface tension and wettability on the bubble measurement in order to develop precise and reliable S-TOP method. In the present study, we specify the gradient of leading edge (or trailing edge) of the S-TOP signal is proportional to the gas-liquid interface velocity. In the measurement of bubbles and droplets via S-TOP, this relation is effectively utilized. The influences of surface tension and probe-surface wettability on this relation are quantitatively discussed. At surface tension higher than about 50mN/m, the surface tension is dominant. On the other hand, at lower than this value, the wettability is dominant. On the basis of improvement in the consideration of the above results, the authors demonstrate the simultaneous measurement of diameters and velocities of small bubbles with about 200 mm in diameter.

Bubbles and Droplets Measurement via Optical Fiber Probe Processed by Femtosecond Pulse Laser

2008 ◽  
Author(s):  
Takayuki Saito ◽  
Yusuke Ozawa ◽  
Keisuke Matsuda ◽  
Shin-Ichiro Aoshima
Keyword(s):  
Light Intensity ◽  
Optical Fiber ◽  
Pulse Laser ◽  
Simultaneous Measurement ◽  
Femtosecond Pulse ◽  
Detection Characteristic ◽  
Fiber Probe ◽  
Femtosecond Pulse Laser ◽  
Optical Fiber Probe ◽  
Reflected Light

An optical fiber has interesting and useful characteristics, which are able to be applied to scientific measurement. Its phase detection characteristic based on refraction difference between two phases is applied to bubbles/droplets measurement. Recently, demands for measurement of tiny bubbles/droplets increase in research fields of steam injectors, sprays, automotive engines, fine chemical reactors, and so on. Meanwhile, laser science and engineering, particularly femtosecond pulse laser, has made remarkable advances lately. Their unique properties of the interaction between the femtosecond pulses and materials can be utilized for microfabrication. The optical fiber probe methods have been repeatedly improved in order to measure bubbles/droplets efficiently and reliably in gas-liquid two-phase flows. However, one has been taking it for granted that simultaneous measurement of their diameters and velocities needs at least two optical fiber probes. To break through this situation, we newly developed a Single-Tip Optical Fiber Probe (F-STOP) microfabricated by femtosecond pulse laser (fs-pulses) which realizes simultaneous measurement of diameters and velocities of tiny bubbles/droplets. In the F-STOP measurement, the following properties are used to realize the simultaneous measurement of diameters and velocities of bubbles/droplets: the relation between the reflected-light intensity at the wedge-shaped probe tip and the tip-surface area covered with a phase; reflected-light intensity at the groove microfabricated by fs-pulses. The first aim of the present study is to provide data for evaluation of the influences of surface tension and wettability on the bubble measurement in order to develop precise and reliable F-STOP method. The second aim is to describe the process to make F-STOP via fs-pulses. The third aim is demonstration of the newly developed probe in real measurement of bubbles/droplets. On the basis of these, the performance of the new probe is discussed.

555 Clarification of bubble dynamics in a rectangular bubble column via a Four-Tip Optical fiber Probe

2007 ◽  
Vol 2007.56 (0) ◽  
pp. 259-260
Author(s):  
Masamori HIGUCHI ◽  
Chihiro UTSUNOMIYA ◽  
Koichi MORIKAWA ◽  
Takayuki SAITO
Keyword(s):  
Optical Fiber ◽  
Bubble Dynamics ◽  
Bubble Column ◽  
Fiber Probe ◽  
Optical Fiber Probe
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