Direct numerical simulation of bubble rising in turbulence

We investigate the dynamics of bubble rising in homogeneous isotropic turbulence (HIT) of a continuous liquid by performing direct-numerical simulations to fully resolve and analyze the flow in the vicinity of the bubble. An initially spherical bubble of diameter is placed and followed in fully developed HIT for fixed Taylor-scale Reynolds number and in quiescent liquid for comparison. The bubble mean rise velocity is found to decrease with the turbulence intensity related to the role of the nonlinear drag (Ruth et al. 2021). A systematic investigation varying the Froude number (comparing turbulence intensity and buoyancy, from 0.1 to 5), Bond number (comparing buoyancy and surface tension effects, from 0.001 to 2), and Weber number (comparing viscous and surface tension effects, from 0.001 to 2, below break-up threshold) is carried out, together with sensitivity tests in terms of the turbulent Reynolds number. We discuss the reduced rising speed, slip velocity, and bubble-vicinity flow field characteristics as a function of the controlling non-dimensional number.

Ruth, Daniel J, Vernet, Marlone, Perrard, St ́ephane & Deike, Luc 2021 The effect of nonlinear drag on the rise velocity of bubbles in turbulence. Journal of Fluid Mechanics 924, A2.