Constant-energetics physical-space forcing methods for improved convergence to homogeneous-isotropic turbulence with application to particle-laden flows

Bassenne, Maxime; Urzay, Javier; Park, George Ilhwan; Moin, Parviz

doi:10.1063/1.4944629

Cited by 55 publications

(26 citation statements)

References 14 publications

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“…The continuity and linearly forced momentum equations are numerically integrated for the carrier phase, where Π is a hydrodynamic pressure computed from the integration of a Poisson equation obtained by taking the divergence of the momentum equation and making use of the divergence-free constraint for the velocity field 35 . The forcing coefficient A is such that statistically steady homogeneous-isotropic turbulence at constant kinetic energy is maintained 36 . The resulting Taylor–Reynolds number of the simulations is , where λ is the Taylor microscale.…”

Section: Methodsmentioning

confidence: 99%

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Aerodynamic generation of electric fields in turbulence laden with charged inertial particles

Renzo

Urzay

2018

Nat Commun

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Self-induced electricity, including lightning, is often observed in dusty atmospheres. However, the physical mechanisms leading to this phenomenon remain elusive as they are remarkably challenging to determine due to the high complexity of the multi-phase turbulent flows involved. Using a fast multi-pole method in direct numerical simulations of homogeneous turbulence laden with hundreds of millions of inertial particles, here we show that mesoscopic electric fields can be aerodynamically created in bi-disperse suspensions of oppositely charged particles. The generation mechanism is self-regulating and relies on turbulence preferentially concentrating particles of one sign in clouds while dispersing the others more uniformly. The resulting electric field varies over much larger length scales than both the mean inter-particle spacing and the size of the smallest eddies. Scaling analyses suggest that low ambient pressures, such as those prevailing in the atmosphere of Mars, increase the dynamical relevance of this aerodynamic mechanism for electrical breakdown.

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Section: Methodsmentioning

confidence: 99%

“…The initial conditions used for integrating (Eq. ( 19 )) involve a synthetic, solenoidal-isotropic velocity field with a prescribed Passot–Pouquet kinetic-energy model spectrum 36 , 37 .…”

Section: Methodsmentioning

confidence: 99%

Aerodynamic generation of electric fields in turbulence laden with charged inertial particles

Renzo

Urzay

2018

Nat Commun

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“…The initial fluctuating velocity field of the gas carrier phase is generated on the basis of the classical Rogallo's procedure [41] according to a Passot-Pouquet spectrum [42]. A constant-energetics physical-space forced homogeneous isotropic turbulence (HIT) is maintained by resorting to the procedure described in reference [43]. The present computations have been conducted with a Courant and Fourier number values set to 0.1.…”

Section: Computational Setupsmentioning

confidence: 99%

Computational Investigation of Weakly Turbulent Flame Kernel Growths in Iso-Octane Droplet Clouds in CVC Conditions

Zhao

Bouali

Mura

2019

Flow Turbulence Combust

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Numerical simulations of turbulent flame kernel growths in monodisperse clouds of iso-octane liquid droplets are conducted in conditions relevant to constant volume combustors. The simulations make use of a low-Mach number Navier-Stokes solver and a thermodynamic pressure evolution model has been implemented to reproduce the pressure variation that may be issued from either experiments or from a standard (i.e., analytical) compression law. Chemistry is described with a representative skeletal mechanism featuring 29 species and 48 elementary reaction steps. The computational results clearly confirm the enhancement of flame propagation in constant volume combustion conditions. The impact of the droplet diameter on the turbulent flame development is scrutinized for two distinct values of the Stokes number St equal to 0.1 and 1.0. Significant influence on the flame dynamics is put into evidence. This is a direct outcome of the equivalence ratio and temperature heterogeneities, which are themselves very sensitive to the choice of the Stokes number value. Then, small-scale turbulence-scalar interactions (TSI) are studied by analyzing the fields of the scalar gradients and strain-rate. Their dynamics is investigated for both non-reactive and reactive two-phase flows conditions. The TSI analysis is performed on the basis of time evolution equations written for quantities that characterize the couplings between the velocity gradient tensor and scalar gradients vectors. Special emphasis is placed on the possible influence of mass exchange terms between the liquid and gaseous phases.

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“…In order to keep the statistics of the initial fields at the desired values during this simulation, the control-based linear forcing approach of Bassenne et al [28] was used to achieve statistically steady target values of kinetic energy and energy dissipation rate after several large-eddy turn over times. The method suggested in [28] consists of introducing a source term to the momentum equation, in the form of Au. The forcing coefficient A reads…”

Section: Typical Configurationmentioning

confidence: 99%

“…with ( ) and ( ) being the turbulent kinetic energy and the energy dissipation rate, 0 and 0 denote their steady mean values respectively and 0 is the integral time based on 0 and 0 as (2 0 )/(3 0 ). G 1 and G 2 refer to the the controller's time constants set to be less than the Kolmogorov timescale to prevent interference with turbulence energy-containing time scales [28]. The terms B and E are expressed in function of the velocity gradient ∇ u, the Hessians of the velocity vector components H( ) and the molecular viscosity as…”

Section: Typical Configurationmentioning

confidence: 99%

Effects of differential diffusion and stratification characteristic length-scale on the propagation of a spherical methane-air flame kernel

Er-Raiy

Boukharfane

Parsani

2021

AIAA Scitech 2021 Forum

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Early flame kernel development and propagation in globally lean stratified fuel-air mixtures is of importance in various practical devices such as internal combustion engines. In this work, three-dimensional direct numerical simulation (DNS) is used to study the influence of the differential diffusion effects in a globally lean methane-air mixtures in presence of mixture heterogeneities with the goal of understanding the flame kernel behavior in such conditions. The DNS typical configuration corresponds to a homogeneous isotropic flow with an expanding spherical flame kernel. The local forced ignition of the kernel is performed by appending as source term in the sensible enthalpy transport equation that emulates spark ignition by energy deposit for a prescribed duration. The combustion chemistry is described with a skeletal methane-air mechanism, which i) features 14 species and 38 reactions, and ii) uses a multicomponent approach to evaluate transport coefficients. To assess the joint effects of differential diffusion and the stratification characteristic length-scale Φ on the flame kernel development, we considered cases with constant (unitary) and variable fuel Lewis number, both with different values for Φ .

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Constant-energetics physical-space forcing methods for improved convergence to homogeneous-isotropic turbulence with application to particle-laden flows

Abstract: Articles you may be interested in Single-particle Lagrangian and structure statistics in kinematically simulated particle-laden turbulent flows

Cited by 55 publications

References 14 publications

Aerodynamic generation of electric fields in turbulence laden with charged inertial particles

Aerodynamic generation of electric fields in turbulence laden with charged inertial particles

Computational Investigation of Weakly Turbulent Flame Kernel Growths in Iso-Octane Droplet Clouds in CVC Conditions

Effects of differential diffusion and stratification characteristic length-scale on the propagation of a spherical methane-air flame kernel

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