Pulses in the Zero-Spacing Limit of the GOY Model

Ken Haste Andersen, M.H. Jensen, J.L. Nielsen, P. Olesen, Tomas Bohr

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

We study the propagation of localised disturbances in a turbulent, but momentarily quiescent and unforced shell model (an approximation of the Navier-Stokes equations on a set of exponentially spaced momentum shells). These disturbances represent bursts of turbulence travelling down the inertial range, which is thought to be responsible for the intermittency observed in turbulence. Starting from the GOY shell model, we go to the limit where the distance between succeeding shells approaches zero ("the zero spacing limit") and helicity conservation is retained. We obtain a discrete field theory which is numerically shown to have pulse solutions travelling with constant speed and with unchanged form. We give numerical evidence that the model might even be exactly integrable, although the continuum limit seems to be singular and the pulses show an unusual super exponential decay to zero as exp(-constant sigma") when n --> infinity, where a is the golden mean. For finite momentum shell spacing, we argue that the pulses should accelerate, moving to infinity in a finite time. Finally, we show that the maximal Lyapunov exponent of the GOY model approaches zero in this limit. (C) 2000 Elsevier Science B.V. All rights reserved.
Original languageEnglish
JournalPhysica D: Nonlinear Phenomena
Volume138
Issue number1-2
Pages (from-to)44-62
ISSN0167-2789
DOIs
Publication statusPublished - 2000

Keywords

  • Turbulence
  • Shell model
  • GOY model
  • Continuum limit

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