Deformation and initial breakup morphology of viscous emulsion drops in isotropic homogeneous turbulence with relevance for emulsification devices

Håkansson, Andréas; Methodolog, Luca Brandt

doi:10.1016/j.ces.2022.117599

Cited by 11 publications

(16 citation statements)

References 73 publications

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“…All data can then be rescaled using the parameter α(μ r ) as shown in figure 3 Note that, as discussed by Håkansson (2020), the use of a break-up frequency within a population model must be made in a consistent way. Here, our definition of the break-up frequency has no ambiguity in the region of the break-up diagram where all cases break before 20t c (equivalent to 200τ η , significantly larger than any of the break-up times discussed by Håkansson & Brandt 2022), which is almost all data points except the ones on the boundary (see figure 2). For the parameters close to the boundary, the mean break-up time can become close to the window of observation, and less than 100 % of the ensemble leads to break-up.…”

Section: Drop Break-up Frequencymentioning

confidence: 87%

“…)) occurrence and a reasonable computational cost to perform large ensembles for a wide range of conditions. This time corresponds to 200τ η , the Kolmogorov time scale, so that the time we systematically explore is much longer than the times tested in Håkansson & Brandt (2022), giving strong confidence in the resolution of the break-up boundaries. Note that the time for pinching is smaller than the eddy-turnover time, so when no break-up is observed at high viscosity ratio, it is not due to an incomplete pinching but simply because the conditions leading to break-up have not been met.…”

Section: Critical Weber Numbermentioning

confidence: 99%

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Role of viscosity in turbulent drop break-up

Farsoiya,

Liu,

Daiss

et al. 2023

J. Fluid Mech.

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We investigate drop break-up morphology, occurrence, time and size distribution, through large ensembles of high-fidelity direct-numerical simulations of drops in homogeneous isotropic turbulence, spanning a wide range of parameters in terms of the Weber number $We$ , viscosity ratio between the drop and the carrier flow $\mu _r=\mu _d/\mu _l$ , where d is the drop diameter, and Reynolds ( $Re$ ) number. For $\mu _r \leq 20$ , we find a nearly constant critical $We$ , while it increases with $\mu _r$ (and $Re$ ) when $\mu _r > 20$ , and the transition can be described in terms of a drop Reynolds number. The break-up time is delayed when $\mu _r$ increases and is a function of distance to criticality. The first break-up child-size distributions for $\mu _r \leq 20$ transition from M to U shape when the distance to criticality is increased. At high $\mu _r$ , the shape of the distribution is modified. The first break-up child-size distribution gives only limited information on the fragmentation dynamics, as the subsequent break-up sequence is controlled by the drop geometry and viscosity. At high $We$ , a $d^{-3/2}$ size distribution is observed for $\mu _r \leq 20$ , which can be explained by capillary-driven processes, while for $\mu _r > 20$ , almost all drops formed by the fragmentation process are at the smallest scale, controlled by the diameter of the very extended filament, which exhibits a snake-like shape prior to break-up.

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Section: Drop Break-up Frequencymentioning

confidence: 87%

Section: Critical Weber Numbermentioning

confidence: 99%

Role of viscosity in turbulent drop break-up

Farsoiya,

Liu,

Daiss

et al. 2023

J. Fluid Mech.

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“…By solving the Navier–Stokes equations coupled to a MTHIC volume-of-fluid (VOF) scheme describing the interface 42,58 the evolution of the flow-field and of the drop is followed with high temporal and spatial resolution (spatial resolution corresponding to 41 cells across the initial drop – see ref. 40 for a mesh-dependence study). The temporal resolution is 0.001 τ η , where τ η denotes the Kolmogorov timescale of the turbulent flow,(and ν C denotes kinematic viscosity of the continuous phase).…”

Section: Theory and Computational Methodsmentioning

confidence: 99%

“…40 To compare the behaviour of small versus large drops, we also run a sequence of tests with We = 30, corresponding, approximately, to the behaviour of the largest drops entering an emulsification device. 40,41…”

Section: Theory and Computational Methodsmentioning

confidence: 99%

Emulsifier adsorption kinetics influences drop deformation and breakup in turbulent emulsification

Håkansson,

Nilsson

2023

Soft Matter

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“…In sprays or in emulsions, it is very difficult to track individual drops, and extracting breakup rates from the evolution of the size distributions is extremely challenging (16). Hence, there have been a number of experimental studies in which single drops (or bubbles) are injected and tracked as they pass a turbulent flow region (3,(17)(18)(19)(20)(21)(22)(23). In such experiments, fluid particles are deformed by turbulence and may break before exiting the turbulent region.…”

Section: Introductionmentioning

confidence: 99%

Memoryless drop breakup in turbulence

Vela-Martín

Avila

2022

Sci. Adv.

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The breakup of drops and bubbles in turbulent fluids is a key mechanism in many environmental and engineering processes. Even in the well-studied dilute case, quantitative descriptions of drop fragmentation remain elusive, and empirical models continue to proliferate. We here investigate drop breakup by leveraging a novel computer code, which enables the generation of ensembles of experiments with thousands of independent, fully resolved simulations. We show that in homogeneous isotropic turbulence breakup is a memoryless process whose rate depends only on the Weber number. A simple model based on the computed breakup rates can accurately predict experimental measurements and demonstrates that dilute emulsions evolve through a continuous fragmentation process with exponentially increasing time scales. Our results suggest a nonvanishing breakup rate below the critical Kolmogorov-Hinze diameter, challenging the current paradigm of inertial drop fragmentation.

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Deformation and initial breakup morphology of viscous emulsion drops in isotropic homogeneous turbulence with relevance for emulsification devices

Cited by 11 publications

References 73 publications

Role of viscosity in turbulent drop break-up

Role of viscosity in turbulent drop break-up

Emulsifier adsorption kinetics influences drop deformation and breakup in turbulent emulsification

Memoryless drop breakup in turbulence

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