منابع مشابه
0 M ar 1 99 8 Helicity advection in Turbulent Models
Helicity transfer in a shell model of turbulence is investigated. In particular, we study the scaling behavior of helicity transfer in a dynamical model of turbulence lacking inversion symmetry. We present some phenomenological and numerical support to the idea that Helicity becomes -at scale small enougha passively-advected quantity. “oυτoι συνǫχθǫιν, αλλα συμφιλǫιν ǫφυν” ANTIΓONH “non sono na...
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It is shown that the turbulent dynamo -e ect converts magnetic helicity from the turbulent eld to the mean eld when the turbulence is electromagnetic while the magnetic helicity of the meaneld is transported across space when the turbulence is electrostatic or due to the electron diamagnetic e ect. In all cases, however, the dynamo e ect strictly conserves the total helicity except for a batter...
متن کاملInverse versus Direct Cascades in Turbulent Advection
A model of scalar turbulent advection in compressible flow is analytically investigated. It is shown that, depending on the dimensionality d of space and the degree of compressibility of the smooth advecting velocity field, the cascade of the scalar is direct or inverse. If d . 4 the cascade is always direct. For a small enough degree of compressibility, the cascade is direct again. Otherwise i...
متن کاملSlow modes in passive scalar turbulent advection.
This communication describes the computation of slow modes in a generic shell model of passive turbulent advection. It is argued that the propagator for the correlation functions possesses a ladder of slow modes associated with each zero mode. These slow modes decay algebraically fast, as opposed to exponential. Using the explicit form of the propagator of the 2-point structure function, we sho...
متن کاملTurbulent Dynamos with Shear and Fractional Helicity
Dynamo action owing to helically forced turbulence and large-scale shear is studied using direct numerical simulations. The resulting magnetic field displays propagating wave-like behavior. This behavior can be modelled in terms of an αΩ dynamo. In most cases super-equipartition fields are generated. By varying the fraction of helicity of the turbulence the regeneration of poloidal fields via t...
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ژورنال
عنوان ژورنال: Le Journal de Physique IV
سال: 1998
ISSN: 1155-4339
DOI: 10.1051/jp4:1998618