Spatio-temporal dynamics in a train of rising bubbles

K. Nguyen^a, C.S. Daw^b,a, P. Chakka^a, M. Cheng^a, D.D. Bruns^a, C.E.A. Finney^a, M.B. Kennel^a,b

^aCollege of Engineering University of Tennessee Knoxville TN 37996-2200

^bEngineering Technology Division Oak Ridge National Laboratory Oak Ridge TN 37831-8088

It has been suggested that rising bubbles in dense fluids resemble an inverted dripping faucet and that they undergo analogous period-doubling bifurcations to chaos. We present experimental results demonstrating that this analogy is weak because the dominant source of instability in the bubble train is inherently different -- mutual interactions between spatially separated bubbles as opposed to nozzle dynamics. Unlike the dripping faucet, the initial instability in a bubble train develops at a location far from the injection nozzle and progresses toward the the nozzle with increasing gas flow. From both qualitative and rigorous quantitative observations, we conclude that rising-bubble dynamics is best described as "small-box spatio-temporal chaos" with a flow instability. Such dynamics can superficially appear to be simple temporal chaos when considering spatially localized measurements. We show similarity between our experimental results and a bubble-interaction model that accounts for drag and coalescence effects without considering any nozzle dynamics.

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Nguyen K, Daw CS, Chakka P, Cheng M, Bruns DD, Finney CEA, Kennel MB (1996). Spatio-temporal dynamics in a train of rising bubbles. Chemical Engineering Journal 64(1): 191-197.

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