Acceleration of small heavy particles in homogeneous shear flow: direct numerical simulation and stochastic modelling of under-resolved intermittent turbulence

Barge, Alexis; Gorokhovski, Mikhael

doi:10.1017/jfm.2020.162

Cited by 12 publications

(6 citation statements)

References 79 publications

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“…= ̅ + ′ (9) The filtered Navier Stokes equations and the liquid volume fraction transport equation are given by Eq. (10)(11).…”

Section: = ∫ ( )mentioning

confidence: 99%

“…Based on the works of [9][10][11], in this study we attempt to account for the intermittency effects of residual scale turbulence on the SGS interface dynamics by providing in the filtered momentum equation an access to the fluid acceleration on residual scales as shown in Eq. (11).…”

Section: Les-ssam -Stochastic Sgs Acceleration Modelmentioning

confidence: 99%

“…( 15) while = ⁄ is the relaxation time, is the diffusion time represented by the Kolmogorov time scale giving a short-time correlation for the fluctuations of the orientation vector. Earlier assessments of this approach [9,11] with DNS statistics of fluid particle acceleration in HIT and homogenously sheared turbulence has shown the ability to accurately predict the non-gaussian statistics of acceleration on relatively coarse grids compared to classical LES. The surrogate velocity field obtained from solution of Eq.…”

Section: Les-ssam -Stochastic Sgs Acceleration Modelmentioning

confidence: 99%

“…Based on similar principles, in this paper an attempt is made to present the LES of primary atomization of a diesel spray jet using VOF method accounting for intermittency effects on sub-grid scale liquid/gas interface dynamics. The principal idea is to obtain a full realization of the velocity field by forcing the filtered Navier Stokes equation by the subgrid acceleration, which is modelled in a way to represent the main statistical properties of intermittency in the high Reynolds number flows as outlined in [9][10][11]. This approach is referred to as LES-SSAM (stochastic sub-grid scale method).…”

Section: Introductionmentioning

confidence: 99%

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Stochastic sub-grid scale acceleration model (SSAM) for LES of primary atomization using iso-advector VOF method for ECN Spray-A

Oruganti

Gorokhovski

2021

ICLASS

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Primary atomization at high Weber numbers evolves in highly sheared gas flow. The latter is characterized by energetic intermittent turbulent structures on small length-scales. Although the effects of turbulent flow dynamics on small scales may strongly correlate with wrinkling of the liquid/gas interface, the residual scales are usually discarded in reduced simulations. In this paper, we present the large eddy simulation (LES) of primary atomization of a diesel spray jet using VOF method accounting for intermittency effects on sub-grid scale liquid/gas interface. The principal idea of this approach is to force the filtered Navier Stokes equation by the subgrid acceleration, which is modelled in a way to represent the main statistical properties of intermittency in the high Reynolds number flows. Earlier, this approach was referred to as LES-SSAM (stochastic subgrid acceleration model). In this approach, the statistics of acceleration on residual scales is modelled by two independent stochastic processes i.e., one for the norm and the other for the unit orientation vector. The both are modelled by Ornstein-Uhlenbeck process: while the norm is modelled by a long-correlated log-normal process, the acceleration orientation vector is modelled by diffusion on the unit sphere with relaxation towards the local vorticity field, and with correlation on the short Kolmogorov time. The resulting stochastic velocity field is then used for reconstruction of the liquid/gas interface in the framework of iso-advector geometrical VOF method. The approach is applied to simulate the primary atomization of ECN Spray-A injector. A qualitative comparison of liquid/gas interface evolution with the under-resolved LES-VOF approach is provided.

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“…= ̅ + ′ (9) The filtered Navier Stokes equations and the liquid volume fraction transport equation are given by Eq. (10)(11).…”

Section: = ∫ ( )mentioning

confidence: 99%

Section: Les-ssam -Stochastic Sgs Acceleration Modelmentioning

confidence: 99%

Section: Les-ssam -Stochastic Sgs Acceleration Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Stochastic sub-grid scale acceleration model (SSAM) for LES of primary atomization using iso-advector VOF method for ECN Spray-A

Oruganti

Gorokhovski

2021

ICLASS

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“…Recently, LES-SSAM is revisited in Sabelnikov, Barge & Gorokhovski (2019). In Barge & Gorokhovski (2020), LES-SSAM is further developed for shear flows. In LES-SSAM, the filtered Navier-Stokes equations are locally driven by the stochastic force.…”

Section: Introductionmentioning

confidence: 99%

Stochastic models for the droplet motion and evaporation in under-resolved turbulent flows at a large Reynolds number

Gorokhovski

Oruganti

2021

J. Fluid Mech.

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In this work we introduce a Lagrangian stochastic model for particle motion and evaporation to be used in large-eddy simulations (LES) of turbulent liquid sprays. Effects of small-scale intermittency, usually under-resolved in LES, are explicitly included via modelling of the energy dissipation rate seen by a droplet along its trajectory. Namely, the dissipation rate is linked to the norm of the droplet sub-filtered acceleration which is included in the droplet motion equation. This norm, along with the direction of the droplet sub-filtered acceleration, is simulated as a stochastic process. With increasing Reynolds number, the distribution of the sub-filtered acceleration develops longer tails, with a slower decay in auto-correlation functions of the norm and direction of this acceleration. The stochastic models are specified for particles larger and smaller the Kolmogorov length scale. The assumption of the droplet evaporation model is similar, i.e. the evaporation rate is strongly enhanced when a droplet is subjected to very localized zones of intense velocity gradients. Thereby, the overall evaporation process is assumed to be a succession of two steady-state sub-processes with equal intensities, i.e. evaporation and vapour mixing. Then the stochastic properties of the overall evaporation rate are also controlled by fluctuations of the energy dissipation rate along the droplet path, and with increasing Reynolds number, the intensity of fluctuations of this rate is also increasing. The assessment of the presented stochastic models in LES of high-speed non-evaporating and evaporating sprays show the accurate prediction of experimental data on relatively coarser grids along with a remarkably weaker sensitivity to the grid spacing. The joint statistics and Voronoi tessellations exhibit strong intermittency of evaporation rate. The intensity of turbulence along the droplet pathway substantially promotes the vaporization rate.

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Numerical analysis of vortex formation and particle dispersion in a supersonic compressible particle-laden mixing layer

2023

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Acceleration of small heavy particles in homogeneous shear flow: direct numerical simulation and stochastic modelling of under-resolved intermittent turbulence

Cited by 12 publications

References 79 publications

Stochastic sub-grid scale acceleration model (SSAM) for LES of primary atomization using iso-advector VOF method for ECN Spray-A

Stochastic sub-grid scale acceleration model (SSAM) for LES of primary atomization using iso-advector VOF method for ECN Spray-A

Stochastic models for the droplet motion and evaporation in under-resolved turbulent flows at a large Reynolds number

Numerical analysis of vortex formation and particle dispersion in a supersonic compressible particle-laden mixing layer

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