Interaction between a large buoyant bubble and turbulence

Abstract

International audienceThe free rise of isolated, deformable, finite-size bubbles in otherwise homogeneous isotropic turbulence is investigated by direct numerical simulation. The Navier-Stokes equations are solved in both phases subject to the pertinent velocity and stress conditions at the deformable gas-liquid interface. The bubble rise velocity is found to be drastically reduced by turbulence, as is widely known for microbubbles. The probability distribution functions of the horizontal bubble acceleration component are well fitted by a log-normal distribution. The distributions of the vertical components are negatively skewed, a property related to the fact that bubbles experience on average stronger decelerations than accelerations. An assessment of the correlations of bubble acceleration with properties of the surrounding flow is used to define estimates of the liquid velocity and vorticity entering in liquid acceleration and lift forces. Finally, fast rising bubbles are found to preferentially sample downflow regions of the flow, whereas those subjected to a higher turbulence level have an increased residence time in swirling regions, some features similar to those of small bubbles

Flight-crash events in superfluid turbulence

“…It then follows that the inhomogeneity and anisotropy of the He II flows studied here are likely not sufficient to explain the reported disagreement with respect to the classical numerical results. Similarly, we may also disregard the influence of the particle inertia because numerical evidence of flight-crash events has been found, in homogeneous and isotropic turbulence, not only for tracers (Lévêque & Naso 2014), but also for large buoyant bubbles (Loisy & Naso 2017) and inertial particles (Bhatnagar et al. 2018).…”

Sub-Hinze scale bubble production in turbulent bubble break-up

“…However, it has been shown by Rosales & Meneveau (2005) that by forcing the medium with a force proportional to the velocity in every point of space we can create a well characterized homogeneous and isotropic turbulent flow with properties similar to those obtained with a spectral code. Such an approach has been followed by various numerical studies: Naso & Prosperetti ( 2010) used a linear forcing to study the interaction between a fixed solid sphere and turbulence, Duret et al (2012) investigated evaporation and mixing processes in turbulent two-phase flows while Toutant et al (2008) and Loisy & Naso (2017) used this method to study a rising bubble in a turbulent flow. This idea has been previously implemented and is provided as an example on the Basilisk website (http:// basilisk.fr/src/examples/isotropic.c).…”

“…More recently, Mukherjee et al (2019) used the lattice Boltzmann method to study droplet-turbulence interactions and quasi-equilibrium dynamics in turbulent emulsions. Rising deformable bubbles in turbulence have been studied by Loisy & Naso (2017) with a modified level-set method. Soligo, Roccon & Soldati (2019) used the phase field approach to study the breakage, coalescence and size distribution of surfactant-laden droplets in a turbulent flow.…”

Experimental investigation of the acceleration statistics and added-mass force of deformable bubbles in intense turbulence

“…From breaking waves (Deane & Stokes 2002) and free surface turbulence (Yu, Hendrickson & Yue 2020) to chemical and nuclear reactors (Michiyoshi & Serizawa 1986;Jakobsen 2008), two-phase flows consisting of finite-sized deformable bubbles or droplets are ubiquitous in nature and industrial applications. Their complicated interaction with the surrounding turbulent flows poses significant challenges to both numerical and experimental methods (Verschoof et al 2016;Loisy & Naso 2017;Alméras et al 2019;Du Cluzeau, Bois & Toutant 2019), as the interface deformation tends to modulate many hydrodynamic forces experienced by bubbles/droplets. In particular, it is well known that additional fluid forces tend to act upon an object as it accelerates relative to its surrounding flow; in turbulence, however, this relative acceleration between the two phases could originate either from the unsteady turbulent background flow or bubble/droplet deformation.…”