Modulation of homogeneous and isotropic turbulence by sub-Kolmogorov particles: Impact of particle field heterogeneity

Letournel, Roxane; Laurent, Frédérique; Massot, Marc; Vié, Aymeric

doi:10.1016/j.ijmultiphaseflow.2020.103233

Cited by 15 publications

(9 citation statements)

References 44 publications

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“…However, the proposed modeled LES considers each effect (i.e., the increased particle dissipation and the reduced fluid dissipation) separately and does not rely on compensation of errors. It is known from the literature that for Stokes numbers that are not significantly smaller than one, the total dissipation in a particle-laden flow is increased [19][20][21]23], which also applies to the Stokes numbers investigated in the present study. The total dissipation has contributions from the particles and the fluid, as it occurs in a single-phase flow.…”

Section: B Two-way Coupled Configurationssupporting

confidence: 71%

“…Extensive research has been carried out to better understand the modulation of turbulence by particles. Studies of forced and decaying homogeneous isotropic turbulence (HIT) have shown that the presence of particles can modify the total dissipation in two ways [19][20][21][22][23]:…”

Section: Introductionmentioning

confidence: 99%

“…(i) The particles can remove from or add kinetic energy to the turbulent flow. The sign of the particle kinetic energy transfer and the scales at which the kinetic energy transfer occurs have been shown to depend on at least three parameters: the Stokes number, the particle number density, and the mass fraction [21]. (ii) The fluid dissipation is influenced by the presence of particles [19].…”

Section: Introductionmentioning

confidence: 99%

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An efficient model for subgrid-scale velocity enrichment for large-eddy simulations of turbulent flows

2022

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In some applications of large eddy simulation (LES), e.g., to multiphase turbulent flows, in addition to providing a closure model for the subgrid-scale stress tensor, it is necessary to also provide means to approximate the subgrid-scale velocity field. In this work, we derive a new model for the subgrid-scale velocity that can be used in such LES applications. The model consists in solving a linearized form of the momentum equation for the subgrid-scale velocity using a truncated Fourier-series approach. Solving within a structured grid of statistically homogeneous sub-domains enables the treatment of inhomogeneous problems. It is shown that the generated subgrid-scale velocity emulates key properties of turbulent flows, such as the right kinetic energy spectrum, realistic strain-rotation relations and intermittency. The model is also shown to predict the correct inhomogeneous and anisotropic velocity statistics. The computational costs of the model are still of the same order as the costs of the LES.

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Section: B Two-way Coupled Configurationssupporting

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An efficient model for subgrid-scale velocity enrichment for large-eddy simulations of turbulent flows

2022

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“…Analysing the turbulent energy spectrum in two-way coupling suggested that particles attenuate energy at low wavenumbers and augment it at high wavenumbers (Letournel et al. 2020), and this effect enhances with the rise in particle number density (Hassaini & Coletti 2022). The increase in small-scale energy escalates , the rate of energy transfer from the large to small scales, growth rate, and drops (Elghobashi & Truesdell 1993).…”

Section: Introductionmentioning

confidence: 99%

Viscosity-modulated clustering of heated bidispersed particles in a turbulent gas

Saieed,

Hickey

2024

J. Fluid Mech.

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Clustering of externally and evenly heated particles is enhanced by the increased viscosity of heated fluid in the vicinity of these clusters – a phenomenon known as viscous capturing (VC). Herein we study, via direct numerical simulations of decaying turbulence, the effect of temperature-driven viscosity on clustering with different particle loading densities. We employ a two-way momentum and energy coupling, and gas viscosity is modelled by a power law to understand the role of the increased drag and particle back-reaction force on the clustering intensity. For the continuum and dispersed phases, Eulerian and Lagrangian point particle schemes have been used, neglecting inter-particle collisions. We found that the enhanced viscosity-driven clustering is a strong function of particle loading density, as the increase in particle number density enables the formation of large uneven clusters before heating, which is the main condition for VC to take effect. Higher number density should result in greater turbulence modulation and negate local temperature-based viscous effects leading to VC. However, due to higher local particle number density in the clusters and interphase heat transfer, increased drag force prevails in such cases and delivers excessive clustering. By sampling conditionally the particle velocity and temperature inside the clusters, it is found that the thermodynamic and kinematic properties of the particles in the clusters are highly correlated, and this correlation increases with the particle loading density. Therefore, based on the particle number density, temperature-based viscosity can enhance considerably the clustering of heated particles and alter the effect of particles on the underlying turbulence.

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“…The Large Eddy simulation (LES) is widely used to understand and predict turbulent particleladen flows. The most classical way consists in combining a single-phase LES model to describe the gas phase, with a LES model for the particulate phase.The objective of a LES particle model is to recover the DNS statistics and macroscopic trends, such as two-way coupling between the spray and the gas phase [1]. Indeed, the retro-coupling can occur at small scales of the flow, and the LES simulation affects not only the particle phase field, but also the one of the carrier phase because of the missing interactions at small scales of the flow with particles.…”

Section: Introductionmentioning

confidence: 99%

Reproducing segregation and particle dynamics in Large Eddy Simulation of particle-laden flows

Letournel

Laurent

Massot

et al. 2021

ICLASS

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Lagrangian simulations are today widely used for simulating aeronautical chambers. The way droplets are spatially distributed strongly affects the combustion, and accurate modeling and simulation strategies are required. The objective of the present contribution is to investigate how to correctly reproduce preferential concentration in Large Eddy Simulation (LES) of particleladen flows. Looking for a way to recover the DNS statistics, we highlight that stochastic models can fail in retrieving the tracer limit for non-inertial particles. We suggest a new strategy in the spirit of kinematic modeling of turbulence, which makes use of a random field with enforced divergence-free condition and spatial and temporal correlations. We show that the model can retrieve some Lagrangian statistics and in particular, particle segregation. We also suggest another approach for the LES particle model, based on retrieving not DNS statistics but filtered DNS statistics. We show that in this case, stochastic models can be relevant and appropriate.

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Modulation of homogeneous and isotropic turbulence by sub-Kolmogorov particles: Impact of particle field heterogeneity

Cited by 15 publications

References 44 publications

An efficient model for subgrid-scale velocity enrichment for large-eddy simulations of turbulent flows

An efficient model for subgrid-scale velocity enrichment for large-eddy simulations of turbulent flows

Viscosity-modulated clustering of heated bidispersed particles in a turbulent gas

Reproducing segregation and particle dynamics in Large Eddy Simulation of particle-laden flows

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