Sub-Kolmogorov droplet dynamics in isotropic turbulence using a multiscale lattice Boltzmann scheme

TL;DR

This paper investigates the behavior of tiny droplets in turbulent flows using a multiscale lattice Boltzmann model, surpassing previous ellipsoidal shape assumptions and providing detailed insights into droplet deformation and breakup.

Contribution

It introduces a hybrid pseudo-spectral Lattice Boltzmann scheme capable of resolving sub-Kolmogorov droplet dynamics in turbulence beyond traditional ellipsoidal models.

Findings

The model accurately captures droplet deformation and breakup.

Results extend understanding beyond ellipsoidal shape assumptions.

The approach links microscopic droplet behavior with macroscopic turbulence data.

Abstract

The deformation and dynamics of a single droplet in isotropic turbulence is studied using a Lattice Boltzmann diffuse interface model involving exact boundary flow conditions to allow for the creation of an external turbulent flow. We focus on a small, sub-Kolmogorov droplet, whose scale is much smaller than the Kolmogorov length scale of the turbulent flow. The external flow field is obtained via pseudo-spectral simulation data describing the trajectory of a passive tracer in isotropic turbulence. In this way we combine the microscopic scale of the droplet and the macroscopic scale of the turbulent flow. The results obtained from this fully resolved model are compared to previous studies on sub-Kolmogorov droplet dynamics in isotropic turbulent flows, where an analytical model, which assumes the droplet shape to be an ellipsoid at all times, is used to describe the droplet deformation. Our findings confirm, that the hybrid pseudo-spectral Lattice Boltzmann algorithm is able to study droplet deformation and breakup in a regime well beyond the ellipsoidal approximation.