A priori filtering and LES modeling of turbulent two-phase flows application to phase separation

International audienceThe Large Eddy Simulation (LES) of two-phase flows with resolved scale interfaces is investigated through the a priori filtering of Direct Numerical Simulations (DNS) of one-fluid and multifield models. A phase inversion benchmark [ 1 –4] is considered highlighting many coalescence and interface rupture events in a kind of atomization process. The order of magnitude of specific two-phase subgrid LES terms is first considered with the two modeling approaches. Then, different existing models such as Smagorinsky [5], Wall-Adapting Local Eddy-viscosity (WALE) model [6], Bardina [7], Mixed [8] and Approximate Deconvo-lution Model (ADM) [9] are used to account for two-phase subgrid effects. These models are compared to filtered DNS results. The main conclusion concerning a priori LES filtering is that the inertia term is not predominant in two-phase flows with fragmentation and rupture of interface. This conclusion is different from that of the studies of [3, 10–13]. Concerning LES models, functional modeling do not correlate to filtered DNS results whereas structural approaches do. Bardina and ADM are clearly the good LES framework to consider for two-phase flows with resolved scale interfaces. ADM is clearly better than Bardina in our study

A Phase-Conditioned Filtering of Incompressible Interfacial Multiphase Flow Equations: A Priori Study for the Modeling of LES Subgrid Scale Terms

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An a Priori Study for the Modeling of Subgrid Terms in Multiphase Flows

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Direct Numerical Simulation of Particle Turbulence Interaction in Forced Turbulence

International audienceUsually, numerical simulations of two-phase particle dispersed flow both with Eulerian or Lagrangian approaches assume particle size to be smaller than the smallest scales of the carrier fluid, which is not the case for most two-phase dispersed flows. The present work aims at giving a detailed analysis of particle behaviour by performing fully resolved of finite size particle simulations in the case of forced homogeneous isotropic turbulenc

Particle laden turbulent flow: comparison of fully resolved approaches

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Particle laden turbulent flow: comparison of fully resolved approaches

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Assessment of numerical methods for fully resolved simulations of particle-laden turbulent flows

During the last decade, many approaches for resolved-particle simulation (RPS) have been developed for numerical studies of finite-size particle-laden turbulent flows. In this paper, three RPS approaches are compared for a particle-laden decaying turbulence case. These methods are, the Volume-of-Fluid Lagrangian method, based on the viscosity penalty method (VoF-Lag); a direct forcing Immersed Boundary Method, based on a regularized delta function approach for the fluid/solid coupling (IBM); and the Bounce Back scheme developed for Lattice Boltzmann method (LBM-BB). The physics and the numerical performances of the methods are analyzed. Modulation of turbulence is observed for all the methods, with a faster decay of turbulent kinetic energy compared to the single-phase case. Lagrangian particle statistics, such as the velocity probability density function and the velocity autocorrelation function, show minor differences among the three methods. However, major differences between the codes are observed in the evolution of the particle kinetic energy. These differences are related to the treatment of the initial condition when the particles are inserted in an initially single-phase turbulence. The averaged particle/fluid slip velocity is also analyzed, showing similar behavior as compared to the results referred in the literature. The computational performances of the different methods differ significantly. The VoF-Lag method appears to be computationally most expensive. Indeed, this method is not adapted to turbulent cases. The IBM and LBM-BB implementations show very good scaling.Accepted Author ManuscriptFluid MechanicsMulti Phase System