Large-eddy simulation of particle-laden turbulent flows

TLDR

Large‑eddy simulation offers a framework for modeling turbulent sprays. The study investigates the capabilities and validity of the closure models, particularly SGS dispersion, by applying the approach to a dilute particle‑laden turbulent mixing layer. The method solves filtered gas‑phase transport equations with droplet source terms, coupled to a probabilistic liquid‑phase model based on the joint probability density function, and introduces subgrid‑scale modeling for the unclosed filtered Lagrangian rates. The formulation reproduces measured properties of both continuous and dispersed phases, matches experimental droplet–gas turbulence interactions, and reveals a selective energy transfer where few large‑scale frequencies gain energy while others are damped.

Abstract

A large-eddy-based methodology for the simulation of turbulent sprays is discussed. The transport equations for the spatially filtered gas phase variables, in which source terms accounting for the droplet effects are added, are solved together with a probabilistic description of the liquid phase. The probabilistic approach for the liquid phase is based on the transport equation for the spatially filtered joint probability density function of the variables required in order to describe the state of the liquid phase. In this equation, unclosed terms representing the filtered Lagrangian rates of change of the variables describing the spray are present. General modelling ideas for subgrid-scale (SGS) effects are proposed. The capabilities of the approach and the validity of the closure models, with particular with respect to the SGS dispersion, are investigated through application to a dilute particle-laden turbulent mixing layer. It is demonstrated that the formulation is able to reproduce very closely the measured properties of both the continuous and dispersed phases. The large-eddy simulation (LES) results are also found to be entirely consistent with the experimentally observed characteristics of droplet–gas turbulence interactions. Consistent with direct numerical simulation (DNS) studies of isotropic turbulence laden with particles where the entire turbulence spectrum is found to be modulated by the presence of particles, the present investigation, which comprises the effects of particle transport upon the large-scale vortical structures of a turbulent shear flow, highlights what appears to be a selective behaviour; few large-scale frequencies gain energy whereas the remaining modes are damped.