Structural Studies of Decaying Fluid Turbulence: Effect of Initial Conditions

TL;DR

This paper investigates how initial conditions influence the structural evolution of decaying fluid turbulence through numerical simulations, revealing a crossover between non-cascade and cascade behaviors based on initial energy spectra.

Contribution

It provides a systematic numerical comparison of turbulence structures arising from different initial energy spectra, highlighting the conditions leading to energy cascade development.

Findings

Identification of differences in vorticity isosurfaces and energy dissipation rates.

Observation of a crossover between non-cascade and cascade behaviors.

Numerical demonstration of how initial spectra influence turbulence evolution.

Abstract

We present results from a systematic numerical study of structural properties of an unforced, incompressible, homogeneous, and isotropic three-dimensional turbulent fluid with an initial energy spectrum that develops a cascade of kinetic energy to large wavenumbers. The results are compared with those from a recently studied set of power-law initial energy spectra [C. Kalelkar and R. Pandit, Phys. Rev. E, {\bf 69}, 046304 (2004)] which do not exhibit such a cascade. Differences are exhibited in plots of vorticity isosurfaces, the temporal evolution of the kinetic energy-dissipation rate, and the rates of production of the mean enstrophy along the principal axes of the strain-rate tensor. A crossover between non-`cascade-type' and `cascade-type' behaviour is shown numerically for a specific set of initial energy spectra.