How fast do bubbles rise in strong turbulence with a high energy dissipation rate?
ORAL
Abstract
We carried out an experimental study on the rise velocity of finite-size bubbles from 1 mm to 10 mm in diameter in strong turbulence. The turbulence generated in our facility targets an energy dissipation rate close to the one typically experienced in oceanic environments, which is orders-of-magnitude larger than most existing laboratory facilities. To uncover the mechanisms of bubble-turbulence interaction and its effect on the bubble rising velocity, simultaneous measurements of both the dispersed and the carrier phases in 3D were obtained. The results suggest that the bubble rising velocity shows an interesting transition: small bubbles rise much slower and large bubbles rise faster than that in the quiescent medium. In addition, the transition is at the point when bubble deformation becomes important. A simple model is introduced to quantify this transition and use it to infer both the lift and drag coefficients.
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