Spatial Structure and Velocity Fluctuations in Turbulent Bubble Jets in Microgravity
Pau Bitlloch, Xavier Ruiz, Laureano RamÍrez-Piscina and Jaume Casademunt
We study the dynamics of turbulent jets of bubbles created by the injection of a slug flow into a quiescent cavity, both theoretically and experimentally using data from drop tower experiments. The generated bubble jets exhibit a remarkably low degree of coalescence leading to virtually monodisperse suspensions of spherical bubbles. The turbulence of the jet is responsible for the spatial dispersion of the bubble distribution in roughly conical jets.
We propose a stochastic model for the dispersion of bubbles in the jet, in which the statistics of bubble concentration is computed within a k-ε model of turbulence, coupled to a Langevin dynamics with an inhomogeneous diffusivity. Numerical integration is compared to experimental data, focussing on the spatial structure of the bubble jet. Results show that bubble interactions can be neglected as far as spatial dispersion is concerned, even though bubbles are not strictly passive tracers.
Keywords: Bubbles, turbulence, jet, microgravity