Impact of Homogeneous Pressure Perturbation on the Dynamics of Bubble Collapse and Coalescence in a Single and Multi-Bubble Systems*

The objective of this study is investigation of the influence of homogeneous pressure perturbation on rising bubble morphology by analyzing shear stress and strain effects at the bubble-liquid interface. A numerical model is developed using the finite volume method with a Dirichlet pressure-inlet boundary and side walls, capturing bubble dynamics qualitatively and quantitatively, and validated with RMSE <1% against experimental data containing optical diagnostics and quantitative measurements, ensuring accurate representation of key parameters like the morphology of the rising bubble and its local velocity during ascent. The numerical model uses approximately 10⁵ elements with a mesh size 0.0025 times the domain dimension, employs volume of fluid scheme for multiphase physics, and achieves stability through relaxation factors of 0.3 for pressure and 0.4 for momentum, along with a geometric reconstruction scheme for volume fraction discretization to capture sharp interfaces between the two phases. The study observed critical bubble behaviors, including deformation, breakup (re-entrant jet), and coalescence. Analysis of non-dimensional numbers (Atwood), compressibility, pressure perturbation strength, perturbation type (planar and radial), and bubble location reveals their individual and collective effects on bubble dynamics. The study offers valuable insights into the interplay between pressure perturbation and rising bubbles with a robust CFD model for multiphase physics.