MASS TRANSFER IN BUBBLE-LADEN FLOWS

We develop and test a Volume of Fluid-based (VoF-based) numerical method to study mass transfer in bubbly flows. The numerical method employs an incompressible Navier-Stokes solver coupled with a VoF method to accurately track bubble interface dynamics. To model species (gas) transport, we implement an advection-diffusion equation that accounts for varying diffusivity and solubility between phases. This approach enables a detailed study of interfacial mass transfer and of the underlying physical mechanisms driving it. We first benchmark our numerical approach upon comparison with existing literature results for simplified cases (planar surface, single static bubble and single rising bubble). Then, we present preliminary results of the dynamics of a large swarm of bubbles in turbulence. Bubbles are initially fully saturated with a specific chemical species and are introduced into a flow where the species is initially not present. The proposed setup triggers mass transfer from the bubbles to the surrounding turbulent flow. The problem of mass transfer in bubble-laden flows is controlled by three main parameters: the Schmidt number, Sc (momentum to mass diffusivity ratio), the bulk Reynolds number, Reb (inertia to viscous forces ratio), and the Weber number, We (inertia to surface tension forces ratio). In particular, we keep Re and We constant and equal to Reb = 10000 and We = 3100, and we vary Sc (Sc = 1 and Sc = 4). Both qualitative and quantitative results highlight the key influence of Sc on the behaviour of the mass transfer rate, and pave the way for future deeper analysis in the field.