Viscosity-modulated breakup and coalescence of large drops in bounded turbulence

Roccon, Alessio; Paoli, Marco De; Zonta, Francesco; Soldati, Alfredo

doi:10.1103/physrevfluids.2.083603

Cited by 48 publications

(54 citation statements)

References 41 publications

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“…The physical explanation for these observations was not provided. Roccon et al (2017) extended the DNS study of Scarbolo et al (2016), described above, by relaxing the restriction of unity viscosity ratio to examine the effects of varying the viscosity of the droplet. Five different values of the dynamic viscosity ratio, µ = 0.01, 0.1, 1, 10, 100, and three values of Weber number, W e = 0.75, 1.5, 3, were studied providing a total of 15 test cases.…”

Section: Droplets Of Size Larger Than the Kolmogorov Length Scale D > ηmentioning

confidence: 99%

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Direct Numerical Simulation of Turbulent Flows Laden with Droplets or Bubbles

Elghobashi

2019

Annu. Rev. Fluid Mech.

225

131

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This review focuses on direct numerical simulations (DNS) of turbulent flows laden with droplets or bubbles. DNS of these flows are more challenging than those of flows laden with solid particles due to the surface deformation in the former. The numerical methods discussed are classified by whether the initial diameter of the bubble/droplet is smaller or larger than the Kolmogorov length scale and whether the instantaneous surface deformation is fully resolved or obtained via a phenomenological model. Also discussed are numerical methods that account for the breakup of a single droplet or bubble, as well as multiple droplets or bubbles in canonical turbulent flows.

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Section: Droplets Of Size Larger Than the Kolmogorov Length Scale D > ηmentioning

confidence: 99%

“…Iso-contours of TKE computed on a plane passing through the channel center are shown in grey scale. Source: Roccon et al (2017) with permission from The American Physical society.…”

Section: Figurementioning

confidence: 99%

Direct Numerical Simulation of Turbulent Flows Laden with Droplets or Bubbles

Elghobashi

2019

Annu. Rev. Fluid Mech.

225

131

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“…The dynamics of a multiphase flow with surfactant is modeled coupling direct numerical simulations of the Navier-Stokes equations with a phase field method to compute the interface dynamics and the surfactant concentration. The phase field method, which we previously used to study the dynamics of large and deformable droplets in turbulent flows [52,55], is here used in a twoorder-parameter formulation to describe interfacial flows with surfactants. In the following, the governing equations of the two order parameters, phase field φ and surfactant concentration ψ, will be derived and then coupled with continuity and Navier-Stokes (NS) equations to describe the hydrodynamics of the system.…”

Section: Governing Equationsmentioning

confidence: 99%

“…This leads to a computational model able to accurately describe interfacial flows with surfactant. In the most general case this approach can handle non-matched properties [16,52]; density and viscosity are defined as a function of the phase field φ. In this work we want to focus on the effect of surfactant solely, so we considered two phases with matched density (ρ = ρ 1 = ρ 2 ) and viscosity (η = η 1 = η 2 ).…”

Section: Hydrodynamicsmentioning

confidence: 99%

Coalescence of surfactant-laden drops by Phase Field Method

Soligo

Roccon

Soldati

2019

Journal of Computational Physics

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In this work, we propose and test the validity of a modified Phase Field Method (PFM), which was specifically developed for large scale simulations of turbulent flows with large and deformable surfactant-laden droplets. The time evolution of the phase field, φ, and of the surfactant concentration field, ψ, are obtained from two Cahn-Hilliard-like equations together with a two-order-parameter Time-Dependent Ginzburg-Landau (TDGL) free energy functional. The modifications introduced circumvent existing limitations of current approaches based on PFM and improve the well-posedness of the model. The effect of surfactant on surface tension is modeled via an Equation Of State (EOS), further improving the flexibility of the approach. This method can efficiently handle topological changes, i.e. breakup and coalescence, and describe adsorption/desorption of surfactant. The capabilities of the proposed approach are tested in this paper against previous experimental results on the effects of surfactant on the deformation of a single droplet and on the interactions between two droplets. Finally, to appreciate the performances of the model on a large scale complex simulation, a qualitative analysis of the behavior of surfactant-laden droplets in a turbulent channel flow is presented and discussed.

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“…Second, a single drop breakup in statistically stationary homogeneous isotropic turbulence was simulated. There are numerical studies of liquid‐liquid dispersions in a decaying turbulent flow, and in a channel flow . These results are very important and necessary, especially for the fundamental understanding of the physics of the systems.…”

Section: Introductionmentioning

confidence: 99%

Single drop breakup in turbulent flow

Komrakova

2019

Can J Chem Eng

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The breakup process of a single drop in homogeneous isotropic turbulence was studied using direct numerical simulations. A diffuse interface free energy lattice Boltzmann method was applied. The detailed visualization of the breakup process confirmed breakup mechanisms previously outlined such as initial, independent, and cascade breakups. High-resolution simulations allowed to visualize another drop breakup mechanism, burst breakup, which occurs when the mother drop has a large volume, and the flow is highly turbulent. The simulations indicate that the type of the breakup mechanism is a strong function of mother drop size and energy input. Large mother drops in highly turbulent flow fields are more likely to burst, producing a large number of drops of the size close to the Kolmogorov length scale. Small drops in moderate turbulence tend to break only once (initial breakup). The interfacial energy of a drop was tracked as a function of time during drop deformation and breakage. The maximum energy level of the deformed mother drop was compared to commonly used estimates of critical energy necessary to break a drop. Our results show that these reference levels of critical energy are usually underestimated. Moreover, in some cases even if the critical energy level was exceeded, the drop did not break because the time of the interaction between the drop and the eddies was not enough to finish the breakup. The numerical insight presented here can be used as a guideline for the selection of assumptions and simplifications behind breakup kernels.

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Viscosity-modulated breakup and coalescence of large drops in bounded turbulence

Cited by 48 publications

References 41 publications

Direct Numerical Simulation of Turbulent Flows Laden with Droplets or Bubbles

Direct Numerical Simulation of Turbulent Flows Laden with Droplets or Bubbles

Coalescence of surfactant-laden drops by Phase Field Method

Single drop breakup in turbulent flow

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