Bag Film Breakup of Droplets in Uniform Airflows

We present novel numerical simulations investigating the bag breakup of liquid droplets. We first examine the viscous effect on drop deformation before the onset of bag breakup, comparing with theory and experiment. Next, a bag film forms at late time and is susceptible to spurious mesh-induced brea...

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Bibliographic Details
Published in:arXiv.org 2023-06
Main Authors: Tang, Kaitao, Adcock, Thomas, Mostert, Wouter
Format: Article
Language:English
Subjects:
Algorithms
Breakup
Computer simulation
Convergence
Deformation effects
Diameters
Droplets
Finite element method
Fluid flow
Grid refinement (mathematics)
Incompressible flow
Numerical methods
Simulation
Statistics
Thin films
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Summary:We present novel numerical simulations investigating the bag breakup of liquid droplets. We first examine the viscous effect on drop deformation before the onset of bag breakup, comparing with theory and experiment. Next, a bag film forms at late time and is susceptible to spurious mesh-induced breakup in numerical simulations, which has prevented previous studies from reaching grid convergence of fragment statistics. We therefore adopt the manifold death (MD) algorithm which artificially perforates thin films once they reach a prescribed critical thickness independent of the grid size, controlled by a numerical parameter \(L_{\rm sig}\). We show grid convergence of fragment statistics when utilising the MD algorithm, and analyse the fragment behaviour and bag film disintegration mechanisms including ligament breakup, node detachment and rim destabilisation. Our choice of the critical thickness parameter \(L_{\rm sig}\) is limited by numerical constraints and thus has not been matched to experiment or theory; consequently, the current simulations yield critical bag film perforation thicknesses larger than experimentally observed. The influence of the MD algorithm configuration on the bag breakup phenomena and statistics will be investigated in future work. We also study the effects of moderate liquid Ohnesorge number (\(0.005 \leq Oh \leq 0.05\)) on the bag breakup process and fragment statistics, where a non-monotonic dependency of the average diameter of bag film fragments on \(Oh\) is found. These results highlight the utility of the MD algorithm in multiphase simulations involving topological changes, and pave the way for physics-based numerical investigations into spume generation at the air-sea interface.
ISSN:2331-8422