Papers by Mikhael Gorokhovski
Proceedings of the Combustion Institute, 2009
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Afin de prendre en compte les effets d'intermittence aux petites échelles de sous-maille, not... more Afin de prendre en compte les effets d'intermittence aux petites échelles de sous-maille, notre proposition est la suivante. Nous remplaçons l'équation de type LES par une équation restituant une approximation du champ de vitesse non-filtrée à l'aide d'un modèle stochastique d'accélération associée au champ résiduel. Ce modèle a été bâti en cohérence avec la connaissance (en majeure partie expérimentale) sur les propriétés spécifiques de l'accélération lagrangienne dans un champ turbulent à grand nombre de Reynolds. Les calculs de la turbulence de type box 3D, homogène isotrope stationnaire, reproduisent qualitativement les observations expérimentales. Abstract : In the present work, in order to take into account the intermittency phenomena, we proposed a new approach to the LES of constant-density flows. In this approach, the main step is to reconstruct an approximation for unfiltered velocity field based on stochastic simulation of non-resolved (unknown) fl...
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Multi-hole gasoline direct injection (GDI) injector sprays have been studied numerically and expe... more Multi-hole gasoline direct injection (GDI) injector sprays have been studied numerically and experimentally. This study is an extension of previous work performed by Rossella Rotondi [1]. The main part of this work fo-cuses on air entrainment and droplet size prediction in the spray plumes under non-evaporating and evaporating conditions, which can have a significant effect on jet to jet interactions, spray propagation and mixture formation. For this purpose, several Continental's special XL gasoline direct injector geometries have been studied includ-ing a 3-hole 90° Cone Angle (CA) and 6-hole 60° CA injectors. The droplet size distributions of 3-hole injector under non-evaporating conditions show sufficient droplets' breakup. Spray penetrations and the air entrainment fields of 3-hole and 6-hole injectors from simulation and experiments under evaporating conditions are quite comparable. Furthermore, the vapour and the air entrainment fields of the 6-hole spray suggest that...
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In this paper, the new extension to the stochastic simulation of primary air-blast atomization is... more In this paper, the new extension to the stochastic simulation of primary air-blast atomization is introduced, and it is assessed by comparison with measurements. The idea of this extension is as follows. In LES of the gas flow, the primary atomization zone (liquid core, network of filaments and detached primary blobs) is viewed as immersed porous solid body with the stochastic structure. Namely, such a composite body is flowing with the inlet parameters for the liquid jet, and it is changing randomly its configuration. The statistics of configuration of this immersed body are used as boundary conditions in LES of the gas flow, thereby it is assumed that the jet fragmentation process is faster than the typical time resolved scale in the gas flow. The statistical structure of the immersed body is defined by specifically introduced stochastic particles, moving in the space, and identifying the random position, outwards normal and curvature of the interface between the liquid and the ga...
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This paper is devoted to further modification of the Level Set approach, which is well-known for ... more This paper is devoted to further modification of the Level Set approach, which is well-known for simulation of gas-liquid flows with the interface. In our development, we addressed to the case of a strong velocity gradient at the free interface. This is a typical situation, for example, when this interface interacts with the turbulent flow. In this case, the gradients of the level set scalar, in the vicinity of the interface, increase with time very rapidly. In order to maintain the accuracy of the numerical solution, the Level Set methods are combined usually with the Eikonal equation for a signed distance function from the zero level set. In the standard procedure (Sussman et al., J. Comput. Phys. 114, 1994), in order to be consistent with evolutional type of the Level Set equation, the nonevolutional Eikonal equation is replaced by quasi-evolutional one, with the artificial time providing iterations at each time step. Our idea is to modify the Level Set equation, in such a way th...
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International Conference on Liquid Atomization and Spray Systems (ICLASS)
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International Conference on Liquid Atomization and Spray Systems (ICLASS)
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Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles
In this paper, the stochastic equations of droplet motion in turbulent flow, proposed recently by... more In this paper, the stochastic equations of droplet motion in turbulent flow, proposed recently by Gorokhovski and Zamansky (2018, Phys. Rev. Fluids 3, 3, 034602), are assessed for turbulent spray dispersion in diesel like conditions along with Large Eddy Simulation (LES) for the gaseous flow. For droplets above the Kolmogorov length scale, this model introduces the concept of the stochastic drag, independently of laminar viscosity. For droplets below the Kolmogorov length scale, the model equation does depend on the laminar viscosity through the Stokes drag but the particle motion is stochastically forced. Both the stochastic drag and the stochastic forcing of the Stokes drag equation are based on the simple log-normal stochastic process for the viscous dissipation (ϵ) “seen” along the droplet trajectory. In this paper, this model is applied in the framework of two-way coupling, wherein the turbulence generated by the spray inturn controls the spray dispersion. The criterion for the...
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Physical Review Fluids
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International Journal of Multiphase Flow
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Journal of Turbulence, 2016
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Volume 1: Symposia, Parts A and B, 2006
ABSTRACT
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International Journal of Multiphase Flow, 2003
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Springer Proceedings in Physics, 2009
ABSTRACT The fragmentation equation describes the evolution in time of particles system, when par... more ABSTRACT The fragmentation equation describes the evolution in time of particles system, when particles break up. The turbulent eddy decay is an example of such fragmentation. A collection of tangled trajectories of fluid particle, associated with a turbulent concentrated structure, resembles a “wool ball” of a typical scale r. Once a fluid particle is subjected to an intense acceleration, a new “wool ball” is formed, containing a part of total energy of flow. The population of newly appeared “wool balls” is assumed to be governed by the fragmentation equation, requiring conservation of the total kinetic energy injected on large scales. The question raised is how this energy is distributed in statistical ensemble of such “wool balls”. In this paper, the renormalized form of the fragmentation equation is obtained for arbitrary functions for the spectrum and for frequency of fragmentation. If the frequency of fragmentation is a power function of size, a simple exact solution to this equation is obtained, providing for stationary flux of energy, from large scales towards zero scales. A simple stochastic generation of random field with presumed fractal properties is illustrated. Also, presuming the spectrum of breakup and its frequency in the form of power functions, the exact self-similar solution is obtained on the basis of specifically introduced scaling transformations. Here the specific case is considered, when the breakup frequency is decreasing with decreasing of r. This work contributes to the group-theoretical description of statistically homogeneous turbulence, developed recently by authors in [1, 2, 3].
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37th Aerospace Sciences Meeting and Exhibit, 1999
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38th Aerospace Sciences Meeting and Exhibit, 2000
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Lecture Notes in Computational Science and Engineering, 2007
In this paper, the turbulent cascade with intermittency is presented in the framework of universa... more In this paper, the turbulent cascade with intermittency is presented in the framework of universalities of eddy fragmentation under scaling symmetry. Based on these universalities, the stochastic estimation of the velocity increment at sub-grid scales is introduced in order to simulate the response of light solid particle to inhomogeneity of the flow at small spatial scales. The LES of stationary box turbulence was performed, and the computed Lagrangian statistics of tracking particle was compared with measurements. The main effects from recent experimental study of high Reynolds number stationary turbulence are reproduced by computation. For the velocity statistics, the numerical results were in agreement with classical Kolmogorov 1941 phenomenology. However the distribution of velocity increment, computed at different time lag, revealed the strong intermittency: at time lag of order of integral time scale, the velocity increment was distributed as Gaussian, at small time lags this distribution exhibited the long stretched tails.
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Atomization and Sprays, 2001
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Papers by Mikhael Gorokhovski