scholarly journals Dynamics of Bubbles Rising in Finite and Infinite Media

2003 ◽  
Author(s):  
Charles C. Maneri ◽  
Peter F. Vassallo
Keyword(s):  
High Speed ◽  
Velocity Model ◽  
System Size ◽  
Published Data ◽  
Rise Velocity ◽  
Velocity Measurements ◽  
Video System ◽  
Bubble Sizes ◽  
Quiescent Liquid ◽  
Infinite Media

The dynamic behavior of single bubbles rising in quiescent liquid Suva (R134a) in a duct has been examined through the use of a high speed video system. Size, shape and velocity measurements obtained with the video system reveal a wide variety of characteristics for the bubbles as they rise in both finite and infinite media. This data, coupled with previously published data for other working fluids, has been used to assess and extend a rise velocity model given by Fan and Tsuchiya. As a result of this assessment, a new rise velocity model has been developed which maintains the physically consistent characteristics of the surface tension in the distorted bubbly regime. In addition, the model is unique in that it covers the entire range of bubble sizes contained in the spherical, distorted and planar slug regimes.

Velocity measurements of high temperature high speed flow by hydroxyl tagging velocimetry

2013 ◽  
Author(s):  
Jingfeng Ye ◽  
Zhiyun Hu ◽  
Zhenrong Zhang ◽  
Sheng Wang ◽  
Guohua Li ◽  
...  
Keyword(s):  
High Temperature ◽  
High Speed ◽  
Velocity Measurements ◽  
High Speed Flow ◽  
Speed Flow ◽  
Hydroxyl Tagging Velocimetry

scholarly journals Levitation Methods for Use in the Hyperloop High-Speed Transportation System

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4190 ◽  
Author(s):  
Eric Chaidez ◽  
Shankar P. Bhattacharyya ◽  
Adonios N. Karpetis
Keyword(s):  
Speed Of Sound ◽  
High Speed ◽  
System Size ◽  
Magnetic Suspension ◽  
Air Bearings ◽  
Commercial Aviation ◽  
Simple Theories ◽  
Suspension Systems ◽  
Air Resistance ◽  
High Speed Trains

The Hyperloop system offers the promise of transportation over distances of 1000 km or more, at speeds approaching the speed of sound, without the complexity and cost of high-speed trains or commercial aviation. Two crucial technological issues must be addressed before a practical system can become operational: air resistance, and contact/levitation friction must both be minimized in order to minimize power requirements and system size. The present work addresses the second issue by estimating the power requirements for each of the three major modes of Hyperloop operation: rolling wheels, sliding air bearings, and levitating magnetic suspension systems. The salient features of each approach are examined using simple theories and a comparison is made of power consumption necessary in each case.

scholarly journals High-speed light field camera and frequency division multiplexing for fast multi-plane velocity measurements

2015 ◽  
Vol 23 (19) ◽  
pp. 24910 ◽  
Author(s):  
Andreas Fischer ◽  
Christian Kupsch ◽  
Johannes Gürtler ◽  
Jürgen Czarske
Keyword(s):  
High Speed ◽  
Light Field ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Velocity Measurements

Asymmetric deformation of bubble shape: cause or effect of vortex-shedding?

2014 ◽  
Vol 68 (1) ◽  
Author(s):  
Kamil Wichterle ◽  
Marek Večeř ◽  
Marek Růžička
Keyword(s):  
Vortex Shedding ◽  
High Speed ◽  
Centre Of Mass ◽  
Horizontal Shift ◽  
Low Viscosity ◽  
Bottom Side ◽  
The Difference ◽  
Quiescent Liquid ◽  
Counter Current ◽  
Surface Tension Forces

AbstractTwo perpendicular projections of rising bubbles were observed in counter-current downstream diverging flow. Evidently, the bubbles did not enter the boundary layer at the channel wall and a plug liquid flow assumption was acceptable in our experimental equipment. This confirmed that the experiment was appropriate for simulation of bubble rises in a quiescent liquid column. Recent data obtained by a high-speed camera permitted recording over a period of 60 s. Image analysis by a tailor-made program provided a time-series of quantities related to the position, size, and shape of bubbles. In addition to determination of the aspect ratio of the equivalent oblate ellipsoid, deviation from this shape was investigated in respect of the difference between the bubble’s centre of mass and the geometrical centre of bubble projection. Autocorrelation of the data indicated that the bubble inclination oscillated harmonically with a frequency of 5–10 Hz; cross correlation showed that the horizontal shift of the centre of mass, as well as the horizontal velocity, increased with increasing bubble inclination, and the vertical shift of the centre of mass increased with an increases in the absolute value of the bubble inclination. There is no significant phase shift in the oscillation of these quantities. The bulky bottom side of the bubbles is in accordance with the model of bubble oscillation induced by instability of the equilibrium of gravity and surface tension forces. The oscillation frequency dependence on surface forces (Eötvös number) is evident, while viscosity does not play a significant role in low-viscosity liquids. Therefore, vortex-shedding is more likely to be an effect of the oscillation and not its cause.

Velocity Measurements in Microchannels With a Laser Scanning Microscope and Particle Linear Image Velocimetry

2004 ◽  
Author(s):  
S. H. Chao ◽  
M. R. Holl ◽  
J. H. Koschwanez ◽  
R. H. Carlson ◽  
L. S. Jang ◽  
...  
Keyword(s):  
High Speed ◽  
Laser Scanning ◽  
Frame Rate ◽  
Planar Imaging ◽  
Velocity Measurements ◽  
Optical Sectioning ◽  
One Dimensional ◽  
Microscale Flow ◽  
Imaging Results ◽  
Image Velocimetry

A novel velocity measurement method for microscale flow field characterization is reported, particle linear image velocimetry (PLIV). The method records a series of one-dimensional images that represent the trace of particles in the flow across a one-dimensional imager. Linear imaging results in a faster frame rate than planar imaging, allowing observation of larger microscope magnification or measurement of faster flow rates in real-time than comparable techniques. In contrast to particle image velocimetry (PIV), PLIV does not require high-speed cameras or shutters. Furthermore, PLIV is adaptable to multiple linear imager formats and, as one example, can use laser scanning confocal microscopes (LSCM) that acquire images slowly but with high spatial resolutions and optical sectioning ability. Higher resolution can be obtained for flows where in-plane velocity gradient in the direction of the optical path (z-direction) is important. This paper presents the PLIV algorithm, and demonstrates its utility by measuring Poiseuille flow with 1-μm resolution in a microfluidic environment.

scholarly journals Accuracy of diagnostic testing in primary ciliary dyskinesia

2015 ◽  
Vol 47 (3) ◽  
pp. 837-848 ◽  
Author(s):  
Claire L. Jackson ◽  
Laura Behan ◽  
Samuel A. Collins ◽  
Patricia M. Goggin ◽  
Elizabeth C. Adam ◽  
...  
Keyword(s):  
Sensitivity And Specificity ◽  
Primary Ciliary Dyskinesia ◽  
High Speed ◽  
Diagnostic Testing ◽  
Standard Test ◽  
Diagnostic Process ◽  
Published Data ◽  
Transmission Electron ◽  
Repeated Sampling ◽  
Ciliary Dyskinesia

Diagnosis of primary ciliary dyskinesia (PCD) lacks a “gold standard” test and is therefore based on combinations of tests including nasal nitric oxide (nNO), high-speed video microscopy analysis (HSVMA), genotyping and transmission electron microscopy (TEM). There are few published data on the accuracy of this approach.Using prospectively collected data from 654 consecutive patients referred for PCD diagnostics we calculated sensitivity and specificity for individual and combination testing strategies. Not all patients underwent all tests.HSVMA had excellent sensitivity and specificity (100% and 93%, respectively). TEM was 100% specific, but 21% of PCD patients had normal ultrastructure. nNO (30 nL·min−1 cut-off) had good sensitivity and specificity (91% and 96%, respectively). Simultaneous testing using HSVMA and TEM was 100% sensitive and 92% specific.In conclusion, combination testing was found to be a highly accurate approach for diagnosing PCD. HSVMA alone has excellent accuracy, but requires significant expertise, and repeated sampling or cell culture is often needed. TEM alone is specific but misses 21% of cases. nNO (≤30 nL·min−1) contributes well to the diagnostic process. In isolation nNO screening at this cut-off would miss ∼10% of cases, but in combination with HSVMA could reduce unnecessary further testing. Standardisation of testing between centres is a future priority.

Velocity Measurements Using High-Speed Imaging System for Impact Test

2014 ◽  
Vol 903 ◽  
pp. 187-193 ◽  
Author(s):  
Abdul Aziz Jaafar ◽  
Anwar P.P. Abdul Majeed ◽  
S.M. Sapuan ◽  
Shahnor Basri
Keyword(s):  
High Speed ◽  
Impact Test ◽  
Imaging System ◽  
Velocity Measurements ◽  
Glass Composite ◽  
Free Flight ◽  
High Speed Imaging ◽  
Fibre Glass ◽  
System A ◽  
Kinematic Properties

This paper presents the velocity measurements for an impact test on a laminated fibre-glass composite plate. The free flight kinematic properties of a blunt-nosed cylindrical projectile on the upstream and downstream of a test coupon were measured using a high-speed camera imaging system. A visual geometric detection technique is discussed and it is shown that the uncertainties of velocity measurements are associated with an imposed constraint on the camera viewing area and shutter speed.

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