Impact of trailing wake drag on the statistical properties and dynamics of finite-sized particle in turbulence

TL;DR

This study models the velocity and acceleration of finite-sized particles in turbulence, highlighting the significant influence of wake drag and Faxen corrections on their dynamics, especially at low Reynolds numbers.

Contribution

It introduces a comprehensive Eulerian-Lagrangian model including unsteady and non-Stokesian drag forces, revealing their roles in particle behavior in turbulent flows.

Findings

Drag forces minimally affect acceleration statistics.

Wake-induced non-Stokesian drag influences velocity scaling.

Faxen correction dominates acceleration statistics.

Abstract

We study by means of an Eulerian-Lagrangian model the statistical properties of velocity and acceleration of a neutrally-buoyant finite-sized particle in a turbulent flow statistically homogeneous and isotropic. The particle equation of motion, beside added mass and steady Stokes drag, keeps into account the unsteady Stokes drag force - known as Basset-Boussinesq history force - and the non-Stokesian drag based on Schiller-Naumann parametrization, together with the finite-size Faxen corrections. We focus on the case of flow at low Taylor-Reynolds number, Re_lambda ~ 31, for which fully resolved numerical data which can be taken as a reference are available (Homann & Bec 651 81-91 J. Fluid Mech. (2010)). Remarkably, we show that while drag forces have always minor effects on the acceleration statistics, their role is important on the velocity behavior. We propose also that the scaling relations for the particle velocity variance as a function of its size, which have been first detected in fully resolved simulations, does not originate from inertial-scale properties of the background turbulent flow but it is likely to arise from the non-Stokesian component of the drag produced by the wake behind the particle. Furthermore, by means of comparison with fully resolved simulations, we show that the Faxen correction to the added mass has a dominant role in the particle acceleration statistics even for particle with size in the inertial range.