Extreme Lagrangian acceleration in confined turbulent flow

TL;DR

This study investigates how solid boundaries affect Lagrangian acceleration in confined two-dimensional turbulence, revealing increased intermittency near walls and a sharp transition at a critical radius.

Contribution

It provides new insights into boundary effects on Lagrangian turbulence, highlighting the increased intermittency and defining a Lagrangian boundary layer.

Findings

Lagrangian acceleration is more intermittent in confined domains.

Wall influence on dynamics diminishes at the domain center.

Sharp transition in acceleration flatness at a critical radius.

Abstract

A Lagrangian study of two-dimensional turbulence for two different geometries, a periodic and a confined circular geometry, is presented to investigate the influence of solid boundaries on the Lagrangian dynamics. It is found that the Lagrangian acceleration is even more intermittent in the confined domain than in the periodic domain. The flatness of the Lagrangian acceleration as a function of the radius shows that the influence of the wall on the Lagrangian dynamics becomes negligible in the center of the domain and it also reveals that the wall is responsible for the increased intermittency. The transition in the Lagrangian statistics between this region, not directly influenced by the walls, and a critical radius which defines a Lagrangian boundary layer, is shown to be very sharp with a sudden increase of the acceleration flatness from about 5 to about 20.