Multiscales and cascade in isotropic turbulence

TL;DR

This paper uses an explicit map method to analyze the nonlinear dynamics of energy cascade in isotropic turbulence, revealing its multiscale and chaotic nature through visual evidence and bifurcation analysis.

Contribution

It introduces a novel scale analysis approach that visually demonstrates the Richardson cascade and its multiscale, chaotic characteristics in isotropic turbulence.

Findings

Visual evidence of Richardson cascade

Identification of multiscale structure in turbulence

Observation of period-doubling bifurcations indicating chaos

Abstract

The central problem of fully developed turbulence is the energy cascading process. It has revisited all attempts at a full physical understanding or mathematical formulation. The main reason for this failure are related to the large hierarchy of scales involved, the highly nonlinear character inherent in the Navier-Stokes equations, and the spatial intermittency of the dynamically active regions. Richardson has described the interplay between large and small scales and the phenomena so described are known as the Richardson cascade. This local interplay also forms the basis of a theory by Kolmogorov. In this letter, we use the explicit map method to analyze the nonlinear dynamical behavior for cascade in isotropic turbulence. This deductive scale analysis is shown to provide the first visual evidence of the celebrated Richardson cascade, and reveals in particular its multiscale character. The results also indicate that the energy cascading process has remarkable similarities with the deterministic construction rules of the logistic map. Cascade of period-doubling bifurcations have been seen in this isotropic turbulent systems that exhibit chaotic behavior. The `cascade' appears as an infinite sequence of period-doubling bifurcations.