Numerical simulations reveal wall-induced viscous suppression cuts jet drop radii 30-50% in shallow-layer bubble bursting

The work uses axisymmetric Navier-Stokes solvers with volume-of-fluid interface tracking to hold initial bubble shape fixed while varying the dimensionless bubble-wall distance H/R_b from 0.5 to 4. Even at fixed Ohnesorge number, reducing H/R_b from 3 to 1 shrinks the first jet drop radius by 35% and increases drop count per burst. The mechanism is a no-slip boundary layer that retards the cavity bottom, raising the curvature at the focusing point and thereby elevating viscous dissipation before pinch-off.

Prior deep-pool studies (Deike et al., J. Fluid Mech. 2018) assumed unbounded liquid and therefore over-predicted drop size in any confined geometry. The new semi-empirical scaling collapses data across Oh = 0.005-0.05 and H/R_b > 0.5, offering a correction term linear in 1/H that can be inserted into existing aerosol source functions without re-running full simulations.

Applications extend beyond puddles to thin films on plant leaves, bioreactor headspaces, and post-rain asphalt. In each case the model predicts lower coarse-mode aerosol mass and a shift toward finer particles that remain airborne longer, altering both deposition patterns and pathogen transport estimates.

The chief open question is whether the same scaling survives three-dimensional bubble shape oscillations or surfactant gradients; targeted experiments with high-speed interferometry are required before field deployment.