A fully resolved numerical simulation of turbulent flow past one or several spherical particles

Botto, Lorenzo; Prosperetti, Andréa

doi:10.1063/1.3678336

Cited by 34 publications

(34 citation statements)

References 39 publications

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“…For combustion, mixing of fuel/oxidizer is critical. Scalar mixing is strongly affected by small-scale turbulence structures [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Therefore, when the droplet/ligament size is comparable to the turbulence scale, it is expected that droplets/ligaments would change the small-scale structures, hence mixing.…”

Section: Introductionmentioning

confidence: 96%

Droplet/ligament modulation of local small-scale turbulence and scalar mixing in a dense fuel spray

Shinjo

Xia

Umemura

2015

Proceedings of the Combustion Institute

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In this study, the modulation of turbulence and scalar mixing by finite-size droplets/ligaments in a dense fuel spray is investigated using a DNS (Direct Numerical Simulation) dataset. Ejected from a spray nozzle with a high speed, a liquid-fuel jet deforms and the fuel spray is atomized into many ligaments and droplets. During these processes, the gas flow becomes turbulent due to droplet/ligament dynamics. At the same time, droplet evaporation and mixing with ambient air are affected by the small-scale gas turbulence. An understanding of the mixing characteristics in the dense spray zone is important for modeling spray combustion. In a region where the droplet number density is relatively low, a universal feature of isotropic turbulence was found, although the alignments of strain eigenvectors with vorticity and the mixture fraction gradient are slightly modulated by the presence of droplets, which is a characteristic of particle-laden flows. In gas-phase regions close to droplet surfaces, where the dissipation rate of turbulent kinetic energy is strongly increased, the alignments are more modulated, especially those of the scalar gradient with strain eigenvectors. This can also be seen in the topology similarity among energy dissipation, enstrophy and scalar dissipation in the near field of droplet/ligament surfaces. For the first time, it is found that droplets whose size is comparable to turbulence scales do affect the mixing characteristics in a realistic turbulent spray. This finding has shed new light upon the modeling of flow turbulence and scalar mixing in an evaporating and atomizing fuel spray.

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Section: Introductionmentioning

confidence: 96%

Droplet/ligament modulation of local small-scale turbulence and scalar mixing in a dense fuel spray

Shinjo

Xia

Umemura

2015

Proceedings of the Combustion Institute

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“…For the blob we observe small oscillations of the wake, without vortex shedding at Re P > 300, indicating that some possible transition to unsteady flow could be induced by a small perturbation. In fact, in particle-laden flows typically Re P < 100 [34], and the induction of vortex shedding due to perturbations from the wake of other particle is a more relevant vorticity source.…”

Section: Large Reynolds Numbermentioning

confidence: 99%

“…Even at low Re P , convection of perturbative flow is known to alter the Basset memory and the long time particle dynamics [16]. And vice versa, recent works show that micron-size particles can alter the turbulent spectra at moderate Re P and R ∼ L (with L the Kolmogorov length) [5,6] due to energy dissipation and vorticity production in the particles wake [34].…”

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confidence: 99%

“…Although the point-particle approach can probably describe the relaxational inertia of very small (R/L 1) heavy particles in a light fluid (e.g. aerosol), it has the serious limitation of neglecting the convective inertia arising from the particle finite size [34]. Even at low Re P , convection of perturbative flow is known to alter the Basset memory and the long time particle dynamics [16].…”

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confidence: 99%

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Inertial coupling method for particles in an incompressible fluctuating fluid

Usabiaga

Delgado‐Buscalioni

Griffith

et al. 2014

Computer Methods in Applied Mechanics and Engineering

155

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We develop an inertial coupling method for modeling the dynamics of point-like "blob" The coupling between the fluid and the blob is based on a no-slip constraint equating the particle velocity with the local average of the fluid velocity, and conserves momentum and energy. We demonstrate that the formulation obeys a fluctuation-dissipation balance, owing to the non-dissipative nature of the no-slip coupling. We develop a spatiotemporal discretization that preserves, as best as possible, these properties of the continuum formulation. In the spatial discretization, the local averaging and spreading operations are accomplished using compact kernels commonly used in immersed boundary methods. We find that the special properties of these kernels allow the blob to provide an effective model of a particle; specifically, the volume, mass, and hydrodynamic properties of the blob are remarkably grid-independent. We develop a second-order semi-implicit temporal integrator that maintains discrete fluctuation-dissipation balance, and is not limited in stability by viscosity. Furthermore, the temporal scheme requires only constant-coefficient Poisson and Helmholtz linear solvers, enabling a very efficient and simple FFT-based implementation on GPUs. We numerically investigate the performance of the method on several standard test problems. In the deterministic setting, we find the blob to be a remarkably robust approximation to a rigid sphere, at both low and high Reynolds numbers. In the stochastic setting, we study in detail the short and long-time behavior of the velocity autocorrelation function and observe agreement with all of the known behavior for rigid sphere immersed in a fluctuating fluid. The proposed inertial coupling method provides a low-cost coarse-grained (minimal resolution) model of particulate flows over a wide range of time-scales ranging from 2 Brownian to convection-driven motion.

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“…The method has been thoroughly validated in the original papers and it has proven its value in a number of applications: the sedimentation of 1024 particles [7], the turbulent flow around fixed particles [8,9], the flow induced by a rotating particle [10] and over a porous medium [11,12]. An interesting variant which uses artificial compressibility to generate a timestepping pressure equation has been described and used by Perrin and Hu [13,14].…”

Section: Introductionmentioning

confidence: 98%

Improved procedure for the computation of Lamb’s coefficients in the physalis method for particle simulation

Gudmundsson¹,

Prosperetti²

2013

Journal of Computational Physics

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a b s t r a c tThe PHYSALIS method was designed for the simulation of flows with suspended spherical particles. It differs from standard immersed boundary methods due to the use of a local spectral representation of the solution in the neighborhood of each particle, which is used to bridge the gap between the particle surface and the underlying fixed Cartesian grid. This analytic solution involves coefficients which are determined by matching with the finitedifference solution farther away from the particle. In the original implementation of the method this step was executed by solving an over-determined linear system via the singular-value decomposition. Here a more efficient method to achieve the same end is described. The basic idea is to use scalar products of the finite-difference solution with spherical harmonic functions taken over a spherical surface concentric with the particle. The new approach is tested on a number of examples and is found to posses a comparable accuracy to the original one, but to be significantly faster and to require less memory. A novel test case that we describe demonstrates the accuracy with which the method conserves the fluid angular momentum in the case of a rotating particle.

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A fully resolved numerical simulation of turbulent flow past one or several spherical particles

Cited by 34 publications

References 39 publications

Droplet/ligament modulation of local small-scale turbulence and scalar mixing in a dense fuel spray

Droplet/ligament modulation of local small-scale turbulence and scalar mixing in a dense fuel spray

Inertial coupling method for particles in an incompressible fluctuating fluid

Improved procedure for the computation of Lamb’s coefficients in the physalis method for particle simulation

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