Authors: Yerbol K Akhmetbekov Sergey V Alekseenko Vladimir M Dulin Dmitriy M Markovich Konstantin S Pervunin
Publish Date: 2010/01/01
Volume: 48, Issue: 4, Pages: 615-629
Abstract
A correlationbased processing algorithm for bubble identification by a planar fluorescence for bubble imaging PFBI technique is presented in this paper The algorithm includes procedures to identify bubble positions and sizes as well as to track bubbles and correct bubble displacement vectors Moreover several schemes for calculation time optimisation were realised to achieve a reliable calculation time The developed algorithm identifies and tracks overlapping bubble images or images with nonuniform intensity distributions The employed correlation and iterative passing approach provides subpixel accuracy of bubble displacement estimation In addition the presented algorithm for bubble ring detection can be easily applied to shadow photography images of bubbles after the application of a derivative filter The PFBI technique combined with the particle image velocimetry and particle tracking velocimetry algorithms was applied for the experimental study of bubbly free jet twophase flows at Re = 12000 Four cases of volumetric gas content in the jet core were studied 0 12 24 and 42 with the same mean bubble diameter—085 mm The developed technique measures twodimensional distributions of instantaneous void fractions as well as both gaseous and liquidphase velocities Consequently the mean void fraction and velocity fields and a set of secondorder statistical moments were obtained including correlations of void fraction and velocity pulsations It was shown that the increase in volumetric gas content leads to the suppression of liquidphase velocity fluctuations in the jet mixing layer
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