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Liquid turbulence in dilute bubble plumes

Problem_sketch

(Left) a schematic sketch of a dilute bubble plume and (right) the liquid turbulent kinetic energy budget equation for dilute bubble plumes.

When air bubbles are added into water, they induce motions in the surrounding water via the transfer of their potential energy to the liquid.  In many scenarios, the induced motions create a large vertical movement of water masses and thus mixing in the water column; some examples are subsea oil well blowouts, lake reaeration  projects and natural gas seeps in deep ocean. To control and predict such mixing, it is important to understand and quantify the energy conversion process. By measuring the liquid velocities of a dilute bubble plume formed inside a unstratified, stagnant water tank, the following were found: (1) the turbulent kinetic energy (t.k.e.) production P_B by the bubbles is much larger than that by liquid mean shear; (2) an increasing fraction of the available work done by bubbles is deposited into liquid turbulence as one moves away from the plume centerline and (3) the induced liquid velocity fluctuations in this heterogeneous bubbly flow have very similar characteristics to those of homogeneous bubbly swarms rising with and without a background liquid turbulence, and therefore the fluctuations can possibly be modeled by a universal form.

Lai, C.C.K. and Socolofsky, S.A. (2018). The turbulent kinetic energy budget in a bubble plume (accepted), Journal of Fluid Mechanics. 

Fraga, B., Stoesser, T., Lai, C.C.K. and Socolofsky, S.A. (2016). A LES-based Eulerian-Lagrangian approach to predict the dynamics of bubble plumesOcean Modeling, 97:27-36.

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