Droplets in turbulence: a new perspective

Maxey, Martin

doi:10.1017/jfm.2017.96

Cited by 5 publications

(3 citation statements)

References 8 publications

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“…Interface-capturing simulations of homogenous isotropic turbulence (Dodd and Ferrante, 2016;Perlekar et al, 2012;Komrakova et al, 2015;Bolotnov, 2013) and shear flows (De Vita et al, 2019; have shed some light on the effect of coalescence on turbulence. Notably, Dodd and Ferrante (2016) and Maxey (2017) showed that coalescence is a source of turbulent kinetic energy, while breakup is a sink. Scarbolo et al (2015) investigated the effect of Weber number on breakup and coalescence, Soligo et al (2019) modeled surfactant laden drops in turbulent channel flows, while Bolotnov et al (2011) used the level-set method to simulate bubbly channel flows.…”

Section: Introductionmentioning

confidence: 99%

The effect of droplet coalescence on drag in turbulent channel flows

et al. 2021

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We study the effect of droplet coalescence on turbulent wall-bounded flows by means of direct numerical simulations. In particular, the volume-of-fluid and front-tracking methods are used to simulate turbulent channel flows containing coalescing and non-coalescing droplets, respectively. We find that coalescing droplets have a negligible effect on the drag, whereas the non-coalescing ones steadily increase drag as the volume fraction of the dispersed phase increases: indeed, at 10% volume fraction, the non-coalescing droplets show a 30% increase in drag, whereas the coalescing droplets show less than 4% increase. We explain this by looking at the wall-normal location of droplets in the channel and show that non-coalescing droplets enter the viscous sublayer, generating an interfacial shear stress, which reduces the budget for viscous stress in the channel. On the other hand, coalescing droplets migrate toward the bulk of the channel forming large aggregates, which hardly affect the viscous shear stress while damping the Reynolds shear stress. We prove this by relating the mean viscous shear stress integrated in the wall-normal direction to the centerline velocity.

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Section: Introductionmentioning

confidence: 99%

The effect of droplet coalescence on drag in turbulent channel flows

et al. 2021

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“…Interface-capturing simulations of homogenous isotropic turbulence (Dodd and Ferrante, 2016;Perlekar et al, 2012;Komrakova, Eskin, and Derksen, 2015;Bolotnov, 2013) and shear flows (De Vita et al, 2019; have shed some light on the effect of coalescence on turbulence. Notably, Dodd and Ferrante (2016) and Maxey (2017) showed that coalescence is a source of turbulent kinetic energy, while breakup is a sink. Scarbolo, Bianco, and Soldati (2015) investigated the effect of Weber number on breakup and coalescence, Soligo, Roccon, and Soldati (2019) modelled surfactant laden drops in a turbulent channel flows, while Bolotnov et al (2011) used the level-set method to simulate bubbly channel flows.…”

Section: Introductionmentioning

confidence: 99%

The effect of droplet coalescence on drag in turbulent channel flows

Cannon,

Izbassarov,

Tammisola

et al. 2021

Preprint

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We study the effect of droplet coalescence on turbulent wall-bounded flows, by means of direct numerical simulations. In particular, the volume-of-fluid and front-tracking methods are used to simulate turbulent channel flows containing coalescing and non-coalescing droplets, respectively. We find that coalescing droplets have a negligible effect on the drag, whereas the non-coalescing ones steadily increase drag as the volume fraction of the dispersed phase increases: indeed, at 10% volume fraction, the non-coalescing droplets show a 30% increase in drag, whereas the coalescing droplets show less than 4% increase. We explain this by looking at the wall-normal location of droplets in the channel and show that non-coalescing droplets enter the viscous sublayer, generating an interfacial shear stress which reduces the budget for viscous stress in the channel. On the other hand, coalescing droplets migrate towards the bulk of the channel forming large aggregates, which hardly affect the viscous shear stress while damping the Reynolds shear stress. We prove this by relating the mean viscous shear stress integrated in the wall-normal direction to the centreline velocity.

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“…This has led us to question whether the introduction of droplets actually causes the carrier fluid to contain more energy at high wavenumbers. Also, Maxey (2017) suggests providing a closer analysis of the energy spectrum in his review of Dodd & Ferrante (2016). Furthermore, our interest in the droplets’ effect on the energy spectrum is to help improve subgrid-scale models for large-eddy simulation (LES) of multiphase turbulent flows.…”

Section: Introductionmentioning

confidence: 99%

Wavelet-spectral analysis of droplet-laden isotropic turbulence

Freund

Ferrante

2019

J. Fluid Mech.

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The spectrum of turbulence kinetic energy for homogeneous turbulence is generally computed using the Fourier transform of the velocity field from physical three-dimensional space to wavenumber $k$. This analysis works well for single-phase homogeneous turbulent flows. In the case of multiphase turbulent flows, instead, the velocity field is non-smooth at the interface between the carrier fluid and the dispersed phase; thus, the energy spectra computed via Fourier transform exhibit spurious oscillations at high wavenumbers. An alternative definition of the spectrum uses the wavelet transform, which can handle discontinuities locally without affecting the entire spectrum while additionally preserving spatial information about the field. In this work, we propose using the wavelet energy spectrum to study multiphase turbulent flows. Also, we propose a new decomposition of the wavelet energy spectrum into three contributions corresponding to the carrier phase, droplets and interaction between the two. Lastly, we apply the new wavelet-decomposition tools in analysing the direct numerical simulation data of droplet-laden decaying isotropic turbulence (in absence of gravity) of Dodd & Ferrante (J. Fluid Mech., vol. 806, 2016, pp. 356–412). Our results show that, in comparison to the spectrum of the single-phase case, the droplets (i) do not affect the carrier-phase energy spectrum at high wavenumbers ($k_{m}/k_{min}\geqslant 128$), (ii) increase the energy spectrum at high wavenumbers ($k_{m}/k_{min}\geqslant 256$) by increasing the interaction energy spectrum at these wavenumbers and (iii) decrease the energy at low wavenumbers ($k_{m}/k_{min}\leqslant 16$) by increasing the dissipation rate at these wavenumbers.

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Droplets in turbulence: a new perspective

Cited by 5 publications

References 8 publications

The effect of droplet coalescence on drag in turbulent channel flows

The effect of droplet coalescence on drag in turbulent channel flows

The effect of droplet coalescence on drag in turbulent channel flows

Wavelet-spectral analysis of droplet-laden isotropic turbulence

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