3D chaotic model for sub-grid turbulent dispersion in Large Eddy Simulations

TL;DR

This paper presents a 3D multiscale kinematic velocity model that accurately simulates turbulent dispersion in Large Eddy Simulations by reproducing key dispersion laws and addressing common modeling issues.

Contribution

The authors introduce a novel 3D chaotic velocity field model that captures Lagrangian dispersion and can serve as a sub-grid model in LES of boundary layer flows.

Findings

Successfully reproduces Richardson's law for dispersion

Addresses the sweeping effect in kinematic turbulence models

Can be integrated as a sub-grid model in LES

Abstract

We introduce a 3D multiscale kinematic velocity field as a model to simulate Lagrangian turbulent dispersion. The incompressible velocity field is a nonlinear deterministic function, periodic in space and time, that generates chaotic mixing of Lagrangian trajectories. Relative dispersion properties, e.g. the Richardson's law, are correctly reproduced under two basic conditions: 1) the velocity amplitudes of the spatial modes must be related to the corresponding wavelengths through the Kolmogorov scaling; 2) the problem of the lack of "sweeping effect" of the small eddies by the large eddies, common to kinematic simulations, has to be taken into account. We show that, as far as Lagrangian dispersion is concerned, our model can be successfully applied as additional sub-grid contribution for Large Eddy Simulations of the planetary boundary layer flow.