Curvature Effects in Turbulent Premixed Flames of H2/Air: a DNS Study with Reduced Chemistry

Rocco, G.; Battista, F.; Picano, Francesco; Troiani, G.; Casciola, Carlo Massimo

doi:10.1007/s10494-014-9576-y

Cited by 19 publications

(12 citation statements)

References 46 publications

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“…An Eulerian algorithm directly evolves the gaseous phase dynamics solving the Low-Mach number formulation of the Navier-Stokes equations (1)-(5) (see, e.g., Refs. [36,37] and references therein for validations and tests). A second-order central finite differences scheme is adopted on the staggered grid for space discretization [38], while the temporal evolution is performed by a low-storage third-order Runge-Kutta scheme.…”

Section: Numerical Methods and Modelmentioning

confidence: 99%

Clustering and entrainment effects on the evaporation of dilute droplets in a turbulent jet

Barba

Picano

2018

Phys. Rev. Fluids

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The evaporation of droplets within turbulent sprays involves unsteady, multiscale, and multiphase processes which make its comprehension and modeling capabilities still limited. The present work aims to investigate the dynamics of droplet vaporization within a turbulent spatial developing jet in dilute, nonreacting conditions. We address the problem considering a turbulent jet laden with acetone droplets and using the direct numerical simulation framework based on a hybrid Eulerian-Lagrangian approach and the point droplet approximation. A detailed statistical analysis of both phases is presented. In particular, we show how crucial is the preferential sampling of the vapor phase induced by the inhomogeneous localization of the droplets through the flow. Strong droplet preferential segregation develops suddenly downstream from the inflow section both within the turbulent core and the jet mixing layer. Two distinct mechanisms have been found to drive this phenomenon: the inertial small-scale clustering in the jet core and the intermittent dynamics of droplets across the turbulent-nonturbulent interface in the mixing layer, where dry air entrainment occurs. These phenomenologies strongly affect the overall vaporization process and lead to an impressive widening of the droplet size and vaporization rate distributions in the downstream evolution of the turbulent spray.

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Section: Numerical Methods and Modelmentioning

confidence: 99%

Clustering and entrainment effects on the evaporation of dilute droplets in a turbulent jet

Barba

Picano

2018

Phys. Rev. Fluids

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“…The equations are integrated in time adopting a low-storage, third-order, Runge-Kutta scheme, see e.g. (Battista et al 2014;Rocco et al 2015;Dalla Barba and Picano 2018) for more details. To avoid unphysical oscillations for the mass fraction, Y, in Eq.…”

Section: Theoretical and Numerical Formulationmentioning

confidence: 99%

“…In the present case, only a couple of iterations are sufficient to solve for n+1 and n+1 with a residual smaller than t ≃ 10 −8 . Additional information is provided in the references Battista et al (2014) and Rocco et al (2015).…”

Section: Theoretical and Numerical Formulationmentioning

confidence: 99%

Direct Numerical Simulations of the Evaporation of Dilute Sprays in Turbulent Swirling Jets

Ciottoli

Battista

Galassi

et al. 2020

Flow Turbulence Combust

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The effects of swirled inflows on the evaporation of dilute acetone droplets dispersed in turbulent jets are investigated by means of direct numerical simulation. The numerical framework is based on a hybrid Eulerian–Lagrangian approach and the point-droplet approximation. Phenomenological and statistical analyses of both phases are presented. An enhancement of the droplet vaporization rate with increasing swirl velocities is observed and discussed. The key physical drivers of this augmented evaporation, namely dry air entrainment and swirl-induced centrifugal forces acting on the droplets, are isolated with the aid of additional simulations in which the inertial properties of the droplets are neglected. The correlation between swirl and dry air entrainment rate is found to be responsible for the increase of the global evaporation rate and the spray penetration length reduction, while swirl-induced centrifugal forces are found to be effective only in the jet shear layer, close to the injection orifice, for the analyzed cases.

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“…The numerical results reported in this paper have been computed employing a MPI-parallel code that has been previously used in other numerical studies and has undergone an extensive validation and testing campaign [44,38,14,12]. The numerical algorithm is based on a hybrid Eulerian-Lagrangian approach and the point-droplet approximation.…”

Section: Numerical Methodologymentioning

confidence: 99%

Direct numerical simulation of an evaporating turbulent diluted jet-spray at moderate Reynolds number

Wang,

Barba,

Picano

2020

Preprint

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The evaporation of dispersed, liquid droplets in jet-sprays occurs in several industrial applications and in natural phenomena. Despite the relevance of the problem, a satisfactory comprehension of the mechanisms involved has not still be achieved because of the wide range of turbulent scales and the huge number of droplets involved. In this context, we address a Direct Numerical Simulation of a turbulent jet spray at relatively high Reynolds number, . . = 10, 000. We focus on the effect of the jet Reynolds number on the evaporation process and the preferential segregation of droplets, comparing the outcomes also with a DNS at lower Reynolds number, = 6, 000, in corresponding conditions. The problem is addressed in the hybrid Eulerian-Lagrangian framework employing the point-droplet approximation. Detailed statistical analysis on both the gas and dispersed phases are presented. We found that the droplet vaporization length grows as the bulk Reynolds number is increased from = 6, 000 to = 10, 000 keeping other conditions fixed. We attribute this result to the complex interaction between the inertia of the droplets and the turbulent gaseous phase dynamics.In particular, at higher Reynolds number, the slower droplet mass transfer is not able to comply with the faster turbulent fluctuations of the mixing layer that tend to fasten the process. We also found an intense droplet clustering which is originated by entrainment of dry air in the mixing layer and intensified by the small-scale clustering mechanism in the far-field region. We will show how clustering creates a strongly heterogeneous droplet Lagrangian evolution. All these aspects contribute to the Reynolds-number dependence of the overall droplet evaporation rate. Finally, we discuss the accuracy of the d-square law, often used in spray modeling, for present cases. We found that using this law based on environmental conditions the droplet evaporation rate is overestimated.

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Curvature Effects in Turbulent Premixed Flames of H2/Air: a DNS Study with Reduced Chemistry

Cited by 19 publications

References 46 publications

Clustering and entrainment effects on the evaporation of dilute droplets in a turbulent jet

Clustering and entrainment effects on the evaporation of dilute droplets in a turbulent jet

Direct Numerical Simulations of the Evaporation of Dilute Sprays in Turbulent Swirling Jets

Direct numerical simulation of an evaporating turbulent diluted jet-spray at moderate Reynolds number

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