4,905 research outputs found
Generalized scaling in fully developed turbulence
In this paper we report numerical and experimental results on the scaling
properties of the velocity turbulent fields in several flows. The limits of a
new form of scaling, named Extended Self Similarity(ESS), are discussed. We
show that, when a mean shear is absent, the self scaling exponents are
universal and they do not depend on the specific flow (3D homogeneous
turbulence, thermal convection , MHD). In contrast, ESS is not observed when a
strong shear is present. We propose a generalized version of self scaling which
extends down to the smallest resolvable scales even in cases where ESS is not
present. This new scaling is checked in several laboratory and numerical
experiment. A possible theoretical interpretation is also proposed. A synthetic
turbulent signal having most of the properties of a real one has been
generated.Comment: 25 pages, plain Latex, figures are available upon request to the
authors ([email protected], [email protected]
On the intermittent energy transfer at viscous scales in turbulent flows
In this letter we present numerical and experimental results on the scaling
properties of velocity turbulent fields in the range of scales where viscous
effects are acting. A generalized version of Extended Self Similarity capable
of describing scaling laws of the velocity structure functions down to the
smallest resolvable scales is introduced. Our findings suggest the absence of
any sharp viscous cutoff in the intermittent transfer of energy.Comment: 10 pages, plain Latex, 6 figures available upon request to
[email protected]
Intermittency in Turbulence: computing the scaling exponents in shell models
We discuss a stochastic closure for the equation of motion satisfied by
multi-scale correlation functions in the framework of shell models of
turbulence. We give a systematic procedure to calculate the anomalous scaling
exponents of structure functions by using the exact constraints imposed by the
equation of motion. We present an explicit calculation for fifth order scaling
exponent at varying the free parameter entering in the non-linear term of the
model. The same method applied to the case of shell models for Kraichnan
passive scalar provides a connection between the concept of zero-modes and
time-dependent cascade processes.Comment: 12 pages, 5 eps figure
A lattice Boltzmann study of non-hydrodynamic effects in shell models of turbulence
A lattice Boltzmann scheme simulating the dynamics of shell models of
turbulence is developed. The influence of high order kinetic modes (ghosts) on
the dissipative properties of turbulence dynamics is studied. It is
analytically found that when ghost fields relax on the same time scale as the
hydrodynamic ones, their major effect is a net enhancement of the fluid
viscosity. The bare fluid viscosity is recovered by letting ghost fields evolve
on a much longer time scale. Analytical results are borne out by
high-resolution numerical simulations. These simulations indicate that the
hydrodynamic manifold is very robust towards large fluctuations of non
hydrodynamic fields.Comment: 17 pages, 3 figures, submitted to Physica
Stochastic Resonance in Two Dimensional Landau Ginzburg Equation
We study the mechanism of stochastic resonance in a two dimensional Landau
Ginzburg equation perturbed by a white noise. We shortly review how to
renormalize the equation in order to avoid ultraviolet divergences. Next we
show that the renormalization amplifies the effect of the small periodic
perturbation in the system. We finally argue that stochastic resonance can be
used to highlight the effect of renormalization in spatially extended system
with a bistable equilibria
Emergence of the stochastic resonance in glow discharge plasma
stochastic resonance, glow discharge plasma, excitable medium, absolute mean
differenceComment: St
Approximation of functions of large matrices with Kronecker structure
We consider the numerical approximation of where and is the sum of Kronecker products, that is . Here is a regular
function such that is well defined. We derive a computational
strategy that significantly lowers the memory requirements and computational
efforts of the standard approximations, with special emphasis on the
exponential function, for which the new procedure becomes particularly
advantageous. Our findings are illustrated by numerical experiments with
typical functions used in applications
Homogeneous and Isotropic Turbulence: a short survey on recent developments
We present a detailed review of some of the most recent developments on
Eulerian and Lagrangian turbulence in homogeneous and isotropic statistics. In
particular, we review phenomenological and numerical results concerning the
issue of universality with respect to the large scale forcing and the viscous
dissipative physics. We discuss the state-of-the-art of numerical versus
experimental comparisons and we discuss the dicotomy between phenomenology
based on coherent structures or on statistical approaches. A detailed
discussion of finite Reynolds effects is also presented.Comment: based on the talk presented by R. Benzi at DSFD 2-14. postprint
version, published online on 6 July 2015 J. Stat. Phy
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