Bubble Pinch-Off in Turbulence: Shape Oscillations and Escaping Self-Similarity
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.
D. J. Ruth et al., "Bubble Pinch-Off in Turbulence: Shape Oscillations and Escaping Self-Similarity," Proceedings of the 72nd Annual Meeting of the APS Division of Fluid Dynamics (2019, Seattle, WA), American Physical Society (APS), Nov 2019.
72nd Annual Meeting of the APS Division of Fluid Dynamics (2019: Nov. 23-26, Seattle, WA)
Mechanical and Aerospace Engineering
Article - Conference proceedings
© 2019 American Physical Society (APS), All rights reserved.
26 Nov 2019