Though bubble pinch-off is an archetype of a dynamical system evolving towards a singularity, it has always been described in idealized theoretical and experimental conditions. Using experiments, simulations, and analytical modeling, we consider bubble pinch-off in a turbulent flow, representative of natural conditions in the presence of strong and random perturbations. We show that the turbulence sets the initial conditions for pinch-off, but once the pinch-off starts, the turbulent time at the neck scale becomes much slower than the pinching dynamics: the turbulence freezes. We show that the average neck size, d , can be described by d (t -t0)α , where t0 is the pinch-off, or singularity time, and α 0 . 5 , in close agreement with the axisymmetric theory with zero initial flow. Neck shape oscillations set by the initial conditions are described by a quasi-two-dimensional linear perturbation model, and persistent asymmetries in the neck are related to the complex flow field induced by the deformed bubble shape. In many cases, a three-dimensional kink-like structure forms on part of the neck just before pinch-off, causing d to escape its self-similar decrease.This work was supported by NSF CAREER award CBET 1844932 and American Chemical Society Petroleum Research Fund 59697-DNI9 to L.D.
APS Division of Fluid Dynamics Meeting Abstracts
- Pub Date:
- November 2019