Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · nlin/0302045

Recovering Isotropic Statistics in Turbulence Simulations: The Kolmogorov 4/5th-Law

Mark A. Taylor·Susan Kurien·Gregory L. Eyink
View original source ↗Read source document ↗Export metadata ↓

Abstract

One of the main benchmarks in direct numerical simulations of three-dimensional turbulence is the Kolmogorov 1941 prediction for third-order structure functions with homogeneous and isotropic statistics in the infinite-Reynolds number limit. Previous DNS techniques to obtain isotropic statistics have relied on time-averaging structure functions in a few directions over many eddy turnover times, using forcing schemes carefully constructed to generate isotropic data. Motivated by recent theoretical work which removes isotropy requirements by spherically averaging structure functions over all directions, we will present results which supplement long-time averaging by angle-averaging over up to 73 directions from a single flow snapshot. The directions are among those natural to a square computational grid, and are weighted to approximate the spherical average. The averaging process is cheap, and for the Kolmogorov 1941 4/5ths law, reasonable results can be obtained from a single snapshot of data. This procedure may be used to investigate the isotropic statistics of any quantity of interest.

Explore related subjects

nlin.CD

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Mark A. Taylor, Susan Kurien, Gregory L. Eyink. 2003-02-19. Recovering Isotropic Statistics in Turbulence Simulations: The Kolmogorov 4/5th-Law. https://doi.org/10.1103/physreve.68.026310

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Dynamics and non-integrability of the Swinging Atwood Machine with a massive string: chaos, periodic orbits and resonance structures

Building upon our previous studies on nonlinear variable-length pendulum systems, we investigate the Swinging Atwood Machine with a massive string. In contrast to the classical model, string inertia introduces a configuration-dependent moment of inertia, leading to a modified Hamiltonian structure and substantially richer dynamics. To uncover the global organization of the phase space, we combine Poincaré sections, bifurcation diagrams, and Lyapunov exponent maps with our recently developed numerical framework ,,Lyapunov Refined Maps". This approach provides a unified visualization of periodic, quasi-periodic, chaotic, and terminating motions, revealing intricate resonance networks and high-order periodic structures. We investigate the influence of the string mass, system parameters, and energy by constructing Lyapunov maps in parameter and initial-condition spaces and on fixed-energy surfaces. Liouville integrability is studied within the Morales-Ramis theory. By analyzing the normal variational equations along explicit non-stationary radial solutions and applying the Kovacic algorithm, we prove that the differential Galois group is generically SL(2,C), providing a rigorous obstruction to meromorphic Liouville integrability for every nonzero string mass. Thus, the exceptional integrable case of the classical Swinging Atwood Machine is destroyed by the inclusion of string inertia.

nlin.CD↗
arXiv2026

Nonintegrability theorem on perturbed integrable Hamiltonian dynamical systems with two independent resonances

In this paper we establish a new theorem for nonintegrability of a perturbed, autonomous, two-degree-of-freedom Hamiltonian dynamical system with two independent resonances, based on a criterion which utilizes the well-known theorem of Poincaré and a Lie-series symplectic transformation. We also make certain assumptions and suggestions as to when the theorem holds and when it does not.

nlin.CD↗
arXiv2026

Modal interactions in strongly nonlinear coupled oscillators with closely spaced modes and nonclassical damping distribution

Linear and nonlinear mechanical structures with closely spaced modes and non-classical (nonproportional) damping distribution are susceptible to modal interactions with energy exchanges between modes. In this work we analyze these interactions in a two-degree-of-freedom (2 DoF) coupled oscillator subject to impulse excitation, utilizing action-angle variables and the method of multiple scales. To show the basic steps of the methodology we start from the linear system, then proceed to analyze modal interactions in the system with strongly nonlinear cubic stiffness nonlinearity. In contrast to the linear case, once the dynamics of the nonlinear system is captured in 1:1 resonance, strongly nonlinear modal interactions occur depending on energy. These regimes as well as attraction to capture, 1:1 capture and escape from capture are analyzed in detail. Our analytical study determines the ranges of parameter values for which nonlinear modal interactions due to resonance capture occur. The analytical predictions are fully verified by direct numerical simulations of the governing equations of motion. Possible extensions of the present work to systems of oscillators with more DoF and other types of dissipative elements, e.g., friction or hysteresis are discussed.

nlin.CD↗