Defocusing digital particle image velocimetry: a 3-component 3-dimensional DPIV measurement technique. Application to bubbly flows
This paper describes a three-dimensional imaging system for the purpose of mapping two-phase bubbly flows. The defocusing digital particle image velocimetry 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 velocity field is calculated from the volumetric cross-correlation of consecutive three-dimensional sets of bubble locations. The bubble size information is estimated from the bubble scattered peak intensity. Both quantities correlate following a power law, as predicted by the Mie scattering theory. The technique is applied to the study of the dynamics of sub-millimeter air bubbles in a three-dimensional vortical flow generated by a propeller. Velocity, bubble size distribution and void fraction are briefly discussed.
© 2000 Springer-Verlag. 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, under the supervision of Professor M. V. Heitor (Instituto Superior Técnico, Lisbon). The research was supported by the Office of Naval Research (contract N00014-97-1-0303), under the direction of Dr. E. P. Rood and Dr. M. Hyman. The defocusing digital particle image velocimetry (DDPIV) technology is protected under a US pending patent filed by the California Institute of Technology. The authors would like to thank F. Taugwalder for his expertise in designing the real-time image acquisition system.