E-mail: edward.bolton@yale.edu

Experimental Bubble Induced Vortex Streets

Bubbles rising in a water-filled inclined cell, with a gap spacing of about 4 mm, will generate a vortex street. In a series of experiments with H.F. Bolton, we characterized the terminal velocities, neutral curve, and amplitude and frequency of oscillations observed [Bolton and Bolton, 1988, abst.]. Most studies of periodically forced fluid flows impose the frequency and the amplitude of the forcing. What happens when the forcing frequency is itself created by the flow? We created a cylindrical annulus 20 cm long, with a gap spacing of 2.4 mm and a mean gap diameter of 1.3 cm. The cell was filled with water. A single bubble of air (with a diameter between 4 and 12 mm) was situated in the center of the length, while the axis was horizontal. Upon rotation of this cell, the bubble oscillates from side to side. The generated vortex street rotates with the cylinder, and then forces the bubble at the same frequency as its previous oscillation. Video techniques were used for data acquisition, and the bubble position was digitized to yield a time series. Fourier analysis indicated several regimes (including simply periodic, doubly periodic, and chaotic), in the parameter space of bubble diameter and rotation rate. A simple numerical model of a Hopf bifurcation with delayed feed-back qualitatively yields some of the same results as the experiment [Bolton and Sayler, 1989, abst.].

E.W. Bolton and H.F. Bolton, Vortex street generation and bubble motion in inclined fluid planes, presented at the Division of Fluid Dynamics Meeting of The American Physical Society at Buffalo, NY, Bulletin of the American Physical Society, 33, No. 10, p. 2253, 1988.

E.W. Bolton and B. Sayler, Karman vortex feedback and chaotic bubble motion in a rotating annulus, presented at the Division of Fluid Dynamics Meeting of The American Physical Society at Palo Alto, CA, Bulletin of the American Physical Society, 34, No. 10, p. 2331, 1989.