Lattice Boltzmann simulations of droplet formation in confined channels with thermocapillary flows

Gupta, A.; Sbragaglia, Mauro; Belardinelli, Daniele; Sugiyama, Kazuyasu

doi:10.1103/physreve.94.063302

Cited by 15 publications

(3 citation statements)

References 80 publications

(218 reference statements)

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“…The code has been extensively used and validated in the past by several groups to study: droplet deformation and breakup (Gupta, Sbragaglia & Scagliarini 2015), also in association with thermocapillary (Gupta et al. 2016) and viscoelastic (Gupta & Sbragaglia 2016) effects; droplet formation in microfluidic devices (Chiarello et al. 2017); sliding droplets (Varagnolo et al.…”

Section: Methodsmentioning

confidence: 99%

Lagrangian statistics of concentrated emulsions

Girotto,

Scagliarini,

Benzi

et al. 2024

J. Fluid Mech.

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The dynamics of stabilised concentrated emulsions presents a rich phenomenology including chaotic emulsification, non-Newtonian rheology and ageing dynamics at rest. Macroscopic rheology results from the complex droplet microdynamics and, in turn, droplet dynamics is influenced by macroscopic flows via the competing action of hydrodynamic and interfacial stresses, giving rise to a complex tangle of elastoplastic effects, diffusion, breakups and coalescence events. This tight multiscale coupling, together with the daunting challenge of experimentally investigating droplets under flow, has hindered the understanding of concentrated emulsions dynamics. We present results from three-dimensional numerical simulations of emulsions that resolve the shape and dynamics of individual droplets, along with the macroscopic flows. We investigate droplet dispersion statistics, measuring probability density functions (p.d.f.s) of droplet displacements and velocities, changing the concentration, in the stirred and ageing regimes. We provide the first measurements, in concentrated emulsions, of the relative droplet–droplet separations p.d.f. and of the droplet acceleration p.d.f., which becomes strongly non-Gaussian as the volume fraction is increased above the jamming point. Cooperative effects, arising when droplets are in contact, are argued to be responsible of the anomalous superdiffusive behaviour of the mean square displacement and of the pair separation at long times, in both the stirred and in the ageing regimes. This superdiffusive behaviour is reflected in a non-Gaussian pair separation p.d.f., whose analytical form is investigated, in the ageing regime, by means of theoretical arguments. This work paves the way to developing a connection between Lagrangian dynamics and rheology in concentrated emulsions.

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Section: Methodsmentioning

confidence: 99%

Lagrangian statistics of concentrated emulsions

Girotto,

Scagliarini,

Benzi

et al. 2024

J. Fluid Mech.

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show abstract

“…(1) along with Eqs. (2), (3), (8) and (9), can lead to the Navier-Stokes equations under the low Mach number limitation, and the pressure and the fluid velocity are defined by…”

Section: Methodsmentioning

confidence: 99%

“…In recent decades, the lattice Boltzmann (LB) models have been developed to simulate the multiphase flows. These models mostly fall into one of the following categories 1,2 : the color-gradient model, 3,4 the pseudopotential model, 5–8 the free-energy model, 9–14 and the mean-field theory model. 15 The fluid–structure interaction 16–21 and wettability treatment 4,6,22–24 are the key research hotspots in the LB community.…”

Section: Introductionmentioning

confidence: 99%

Color-gradient lattice Boltzmann modeling of immiscible two-phase flows on partially wetting surfaces

Yuan

Liu

Zhang

2017

Proceedings of the Institution of Mechanical Engineers, Part C:

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A zero-interfacial-force condition is derived and implemented to improve the wetting boundary scheme for a lattice Boltzmann color-gradient model. This new wetting boundary scheme is validated by two static problems, i.e. a droplet resting on a flat surface and a cylindrical surface, and one dynamic problem, i.e. the capillary filling in a two-dimensional channel. In these simulations, we observe that non-physical mass transfer is suppressed and spurious velocities become smaller. Meanwhile, accurate results including dynamic contact line movement are achieved for a broad range of contact angles. The model is then applied to study the displacement of immiscible fluids in a two-dimensional channel. Both the displacement velocity and the change rate of finger length are found to exhibit a linear dependence on the contact angle at the viscosity ratio of unity. The displacement velocity decreases but the change rate of finger length increases with increasing capillary number, while the displacement velocity tends to be constant, i.e. two-thirds of the maximum inlet velocity, at high viscosity ratios or low capillary numbers. In contrast to the displacement velocity, the change rate of finger length is negligible at high viscosity ratios or low capillary numbers, where the finger length is in an equilibrium state, while the equilibrium finger length itself is smaller at a higher viscosity ratio or a lower capillary number.

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