ISSN:
1573-1987
Keywords:
bubbles
;
shape oscillations
;
bubble motion
;
image processing
;
Fourier Descriptors
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The paper details results from an experimental study on bubbles rising in still tap water. Shape and motion parameters of the bubbles were measured using a combination of high speed cinematography and digital image processing. The Reynolds numbers of the bubbles studied ranged from about 700 to 1300, with the bubbles exhibiting all the familiar shape and motion characteristics: oblate spheroids becoming “wobbly”, and spiralling or zig-zagging motion becoming “rocking” as the bubble size increased. Time series of the bubble major axes revealed regular oscillations in the bubble shape. In most cases three frequencies could be readily identified, corresponding to those of vortex shedding from the bubble and two modes of ellipsoidal harmonics (modes 2,0 and 2,2). Comparison of time series of bubble shape and motion indicated a strong interaction between the shape oscillations of mode 2,0 and bubble motion. As the bubble size increased the frequency of both shape oscillation modes approached that of the vortex shedding, which remained constant at about 12 Hz for all of our experiments. The frequencies become equal for bubbles larger than in our study, at a Reynolds number of about 3000. Using data from the literature we found that the vortex shedding appears to become locked-in on the mode 2,0 shape oscillation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1000864525753
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