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J Kockelkoren

Publications and source records attributed to J Kockelkoren.

2 recordsLinked to original sources
PubMed2000

Fixed points, stability, and intermittency in a shell model for advection of passive scalars

We investigate the fixed points of a shell model for the turbulent advection of passive scalars introduced in Jensen, Paladin, and Vulpiani [Phys. Rev. A 45, 7214 (1992)]. The passive scalar field is driven by the velocity field of the popular Gledzer-Ohkitani-Yamada (GOY) shell model. The scaling behavior of the static solutions is found to differ significantly from Obukhov-Corrsin scaling straight theta(n) approximately k(-1/3)(n), which is only recovered in the limit where the diffusivity vanishes, D-->0. From the eigenvalue spectrum we show that any perturbation in the scalar will always damp out, i.e., the eigenvalues of the scalar are negative and are decoupled from the eigenvalues of the velocity. We estimate Lyapunov exponents and the intermittency parameters using a definition proposed by Benzi, Paladin, Parisi, and Vulpiani [J. Phys. A 18, 2157 (1985)]. The full model is found to be as chaotic as the GOY model, measured by the maximal Lyapunov exponent, but is more intermittent.

Journal Article↗
PubMed2000

Comment on "Phase ordering in chaotic map lattices with conserved dynamics"

Angelini, Pellicoro, and Stramaglia [Phys. Rev. E 60, R5021 (1999)] claim that the phase ordering of two-dimensional systems of sequentially updated chaotic maps with conserved "order parameter" does not belong, for large regions of parameter space, to the expected universality class. We show here that these results are due to a slow crossover and that a careful treatment of the data yields normal dynamical scaling. Moreover, we construct better models, i.e., synchronously updated coupled map lattices, which are exempt from these crossover effects, and allow for precise estimates of persistence exponents in this case.

Journal Article↗