# Lagrangian acceleration statistics in a turbulent channel flow

## TL;DR

This study investigates Lagrangian acceleration in turbulent channel flow at high Reynolds number, revealing anisotropic small-scale dynamics influenced by coherent vortices, with implications for modeling dispersion and mixing.

## Contribution

It provides detailed experimental and numerical analysis of acceleration statistics and their dependence on wall distance in turbulent channel flow.

## Key findings

- Strong anisotropy at small scales near the wall
- Impact of coherent vortices on acceleration statistics
- Persistence of anisotropic features across the channel

## Abstract

Lagrangian acceleration statistics in a fully developed turbulent channel flow at $Re_\tau = 1440$ are investigated, based on tracer particle tracking in experiments and direct numerical simulations. The evolution with wall distance of the Lagrangian velocity and acceleration time scales is analyzed. Dependency between acceleration components in the near-wall region is described using cross-correlations and joint probability density functions. The strong streamwise coherent vortices typical of wall-bounded turbulent flows are shown to have a significant impact on the dynamics. This results in a strong anisotropy at small scales in the near-wall region that remains present in most of the channel. Such statistical properties may be used as constraints in building advanced Lagrangian stochastic models to predict the dispersion and mixing of chemical components for combustion or environmental studies.