A quasi-local measure of inter-scale transfer: An approach to understanding turbulence

TL;DR

This paper introduces a new filter-based technique to visualize and analyze instantaneous, spatially-local transfer of kinetic energy across scales in turbulence, enhancing understanding of the underlying physics.

Contribution

It develops a general method for obtaining local scale-to-scale transfer fields, addressing limitations of previous ensemble-averaged measurements.

Findings

The filter approach effectively visualizes instantaneous transfer fields.

Different filters and system constraints impact transfer measurements.

Application to 2D turbulence demonstrates the method's utility.

Abstract

Many questions remain in turbulence research---and related fields---about the underlying physical processes that transfer scalar quantities, such as the kinetic energy, between different length scales. Measurement of an ensemble-averaged flux between scales has long been possible using a variety of techniques, but instantaneous, spatially-local realizations of the transfer have not. The ability to visualize scale-to-scale transfer as a field quantity is crucial for developing a clear picture of the physics underlying the transfer processes and the role played by flow structure. A general technique for obtaining these scale-to-scale transfer fields, called the filter approach, is described. The effects of different filters, finite system size, and limited resolution are explored for experimental and numerical data of two-dimensional turbulence.