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Instantaneous whole field measurement of velocity and size of air microbubbles in two-phase flows using DDPIV

Pereira, F. and Gharib, M. and Dabiri, D. and Modarress, D. (2002) Instantaneous whole field measurement of velocity and size of air microbubbles in two-phase flows using DDPIV. In: Laser techniques for fluid mechanics. Springer , New York, pp. 269-287. ISBN 9783540428374. http://resolver.caltech.edu/CaltechAUTHORS:20130912-105402726

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Abstract

Defocusing digital particle image velocimetry (DDPIV) is the natural extension of digital particle image velocimetry (DPIV), planar or quasi three-dimensional, to a true and unique three-dimensional PIV technique. This work presents the defocusing optical concept by which the depth information can be retrieved, thus overriding the limitation to in-plane measurements of actual PIV techniques, either standard or stereo-based. The concept is implemented into a three-dimensional imaging system specifically designed for the purpose of mapping two-phase bubbly flows. Digital images of the bubble field are recorded and analysed to provide information both on the physical location of every single particle/bubble and on its respective size, which is estimated from the scattered light intensity. The calculation of the true three-component velocity field is done by local spatial cross-correlation between two consecutive sets of particle/bubble locations. The spatial resolution and uncertainty limits are established based on a simplified model of the defocusing optical system. Accuracy measurements show that the average error on the displacements is about 0.02 pixels. The methodology used to measure the size is laid out by application of the Mie scattering theory. A DDPIV prototype instrument was fabricated on specific requirements. The instrument records high resolution images of the bubble field and is capable of providing bubble size and bubble location within a cubic foot volume. The technique is applied to the study of the dynamics of sub-millimeter air bubbles in a three-dimensional vertical flow generated by a propeller. Velocity, bubble size distribution and void fraction for these flows are discussed.


Item Type:Book Section
Additional Information:© 2002 Springer. The visit of Dr. F. Pereira to the C.Q.V. was made possible by a fellowship of the Fundação para a Ciência e a Tecnologia, Portugal. The research was supported by the Office of Naval Research (contract N00014-97-1-0303), under the direction of Dr. Edwin P. Rood and Dr. Mark Hyman. The Defocusing Digital Particle Image Velocimetry (DDPIV) technology is protected under a U.S. pending patent filed by California Institute of Technology.
Group:GALCIT
Funders:
Funding AgencyGrant Number
Fundação para a Ciência e a Tecnologia (Portugal)UNSPECIFIED
Office of Naval Research (ONR)N00014-97-1-0303
Record Number:CaltechAUTHORS:20130912-105402726
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20130912-105402726
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:41288
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:12 Sep 2013 23:03
Last Modified:30 Sep 2016 17:35

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