Fractured Flows: Bursting Bubbles in Dense Suspensions

In contrast to the classical bursting of a bubble in a Newtonian liquid, we show that bubbles in dense suspensions exhibit novel dynamics driven by interfacial instabilities and non-Newtonian rheology. We investigate the bursting dynamics of air bubbles in cornstarch suspensions across a range of mass fractions and reveal three distinct bursting regimes: an inertia-dominated circular opening regime at low mass fractions, a fracture regime at intermediate mass fractions, and a viscous-dominated circular opening regime at high mass fractions. The transition to the fracture regime occurs as the thin suspension film dynamically solidifies, evidenced by a visible change in the film interface from shiny to rough. Remarkably, the fractured films exhibit wrinkling instabilities whose wavelength can be rationalized by accounting for inertial, tensional, and curvature effects. Additionally, we demonstrate that the number of fracture fronts decreases with increasing mass fraction, enabling control over the rupture morphology.