Deformation and Breakup of Oil-Coated Bubbles in Homogeneous Isotropic Turbulence

This study investigates the deformation and breakup dynamics of oil-coated bubbles in homogeneous and isotropic turbulence at turbulent Weber numbers (We_T) of 3, 10, and 30 and Taylor Reynolds number of Re_λ=38. Direct Numerical Simulations (DNS) with adaptive mesh refinement (AMR) are performed using the Basilisk solver. A mesh independence study is conducted with different mesh refinement levels (RL) of 10,11, and 12 (Minimum element size = Domain length/2^RL) by comparing oil-coated bubble size distribution and breakup frequency. The mesh refinement level is set to RL = 11, yielding a size distribution and breakup frequency comparable to those obtained with RL=12. The bubbles are initially fully coated with an oil layer, with an oil volume fraction (φ_o) of 0.3. An effective surface tension is adopted as the sum of the oil–water and air–oil interfacial tensions (σ_eff = σ_ow + σ_ao). The simulations are performed in a periodic cubic domain where statistically stationary turbulence is first generated as a precursor stage. Oil-coated bubbles are then introduced and subjected to different We_T by varying the σ_eff. This study aims to investigate the effect of the turbulent Weber number on bubble breakup dynamics, including breakup frequency and the resulting compound bubble size distribution. This study can contribute to the understanding of interface dynamics and the breakage of compound particles in turbulent flows, such as those released from natural seeps, intentionally generated in flotation processes for particle separation in water, or used in drug delivery applications.