Direct numerical simulations of transient turbulent jets: vortex-interface interactions

Constante-Amores, C. R.; Kahouadji, Lyes; Batchvarov, Assen; Shin, Seungwon; Chergui, Jalel; Jurić, Damir; Matar, Omar

doi:10.1017/jfm.2021.519

Cited by 19 publications

(27 citation statements)

References 68 publications

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“…This hole grows in the spanwise direction and separates the rim from the sheet. In fact, this dynamics has previously been observed by Mirjalili et al (2018) and Constante-Amores et al (2021b). The rest of the β s -Oh space is dominated by surfactant-induced Marangoni stresses which reopen the adjacent sheet to promote droplet detachment via RP instability.…”

Section: Resultssupporting

confidence: 71%

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Role of surfactant-induced Marangoni stresses in retracting liquid sheets

et al. 2022

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In this work, we study the effect of insoluble surfactants on the three-dimensional rim-driven retraction dynamics of thin water sheets in air. We employ an interface-tracking/level-set method to ensure the full coupling between the surfactant-induced Marangoni stresses, interfacial diffusion and inertia. Our findings are contrasted with the (Newtonian) dynamics of a liquid sheet edge, finding that the surfactant concentration can delay, or effectively prevent, the breakup of the rim. Our simulations use the fastest growing Rayleigh–Plateau instability to drive droplet detachment from the fluid sheet (rim). The results of this work unravel the significant role of Marangoni stresses in the retracting sheet dynamics at large elasticity numbers. We study the sensitivity of the dynamics to the elasticity number and the rigidification of the interface.

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Section: Resultssupporting

confidence: 71%

“…(2018) and Constante-Amores et al. (2021 b ). The rest of the space is dominated by surfactant-induced Marangoni stresses which reopen the adjacent sheet to promote droplet detachment via RP instability.…”

Section: Resultsmentioning

confidence: 94%

Role of surfactant-induced Marangoni stresses in retracting liquid sheets

et al. 2022

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“…In our numerical results, we find massive chaotic hairpin vortex structures evolving after the interactions of KH vortices from upstream, which are the primary elements of the jet puff. This observation differs from some other findings in the literature (Zandian et al 2019;Constante-Amores et al 2021), where the mushroom structure is maintained throughout the scope, due to the constant velocity of the injection flow in their works. In fact, magnified views of the hairpin vortical structures show that an appreciable quantity of them are highly asymmetric, which implies that one leg of the hairpin vortex is stronger and longer than the other.…”

Section: Quadrant Analysis Of Turbulence Structure In Multiphase Coug...contrasting

confidence: 99%

“…2019; Constante-Amores et al. 2021), where the mushroom structure is maintained throughout the scope, due to the constant velocity of the injection flow in their works. In fact, magnified views of the hairpin vortical structures show that an appreciable quantity of them are highly asymmetric, which implies that one leg of the hairpin vortex is stronger and longer than the other.…”

Section: Quadrant Analysis Of Turbulence Structure In Multiphase Coug...mentioning

confidence: 99%

Multiphase large-eddy simulations of human cough jet development and expiratory droplet dispersion

Lai

Yan

et al. 2022

J. Fluid Mech.

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Violent respiratory events play critical roles in the transmission of respiratory diseases, such as coughing and sneezing, between infectious and susceptible individuals. In this work, large-scale multiphase flow large-eddy simulations have been performed to simulate the coughing jet from a human's mouth carrying pathogenic or virus-laden droplets by using a weakly compressible smoothed particle hydrodynamics method. We explicitly model the cough jet ejected from a human mouth in the form of a mixture of two-phase fluids based on the cough velocity profile of the exhalation flow obtained from experimental data and the statistics of the droplets’ sizes. The coupling and interaction between the two expiratory phases and ambient surrounding air are examined based on the interaction between the gas particles and droplet particles. First, the results reveal that the turbulence of the cough jet determines the dispersion of the virus-laden droplets, i.e. whether they fly up evolving into aerosols or fall down to the ground. Second, the droplet particles have significant effects on the evolution of the cough jet turbulence; for example, they increase the complexity and butterfly effect introduced by the turbulence disturbance. Our results show that the prediction of the spreading distance of droplet particles often goes beyond the social distancing rules recommended by the World Health Organization, which reminds us of the risks of exposure if we do not take any protecting protocol.

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“…[ 16,17 ] In addition to this, the Hinze correlation (Equation ()) has been studied for other multiphase configurations such as air bubbles in breaking waves, [ 18,19 ] where Deane and Stokes [ 19 ] found We d , crit = 4.7, or for droplets produced in atomization processes. [ 20–22 ]…”

Section: Introductionmentioning

confidence: 99%

Effect of turbulence intensity and surface tension on the emulsification process and its stationary state—A numerical study

et al. 2022

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We study turbulent emulsions and the emulsification process in homogeneous isotropic turbulence (HIT) using direct numerical simulations (DNS) in combination with the volume of fluid method (VOF). For generating a turbulent flow field, we employ a linear forcing approach augmented by a proportional‐integral‐derivative (PID) controller, which ensures a constant turbulent kinetic energy for two phase flow scenarios and accelerates the emulsification process. For the simulations, the density ratio of dispersed and carrier phases is chosen to be similar to that of oil and water (0.9), representing a typical application. We vary the turbulence intensity and the surface tension coefficient. Thus, we modulate those parameters that directly affect the Hinze scale, which is expected to be the most stable maximum droplet diameter in emulsions in HIT. The considered configurations can be characterized with Taylor Reynolds numbers in the range of 100–140 and Weber numbers, evaluated with the velocity fluctuations and the integral length scale, of 4–70. Using the 3‐D simulation results, we study the emulsification process as well as the emulsions at a statistically stationary state. For the latter, droplet size distributions are evaluated and compared. We observe a Hinze scale similarity of the size distributions considering a fixed integral length scale, that is, similar Hinze scales obtained at different turbulence intensities or for different fluid properties result in similar distributions.

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Direct numerical simulations of transient turbulent jets: vortex-interface interactions

Abstract: Abstract

Cited by 19 publications

References 68 publications

Role of surfactant-induced Marangoni stresses in retracting liquid sheets

Role of surfactant-induced Marangoni stresses in retracting liquid sheets

Multiphase large-eddy simulations of human cough jet development and expiratory droplet dispersion

Effect of turbulence intensity and surface tension on the emulsification process and its stationary state—A numerical study

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