2,135 research outputs found
Nonlinear dynamics of flexural wave turbulence
The Kolmogorov-Zakharov spectrum predicted by the Weak Turbulence Theory
remains elusive for wave turbulence of flexural waves at the surface of an thin
elastic plate. We report a direct measurement of the nonlinear timescale
related to energy transfer between waves. This time scale is extracted
from the space-time measurement of the deformation of the plate by studying the
temporal dynamics of wavelet coefficients of the turbulent field. The central
hypothesis of the theory is the time scale separation between dissipative time
scale, nonlinear time scale and the period of the wave (). We
observe that this scale separation is valid in our system. The discrete modes
due to the finite size effects are responsible for the disagreement between
observations and theory. A crossover from continuous weak turbulence and
discrete turbulence is observed when the nonlinear time scale is of the same
order of magnitude as the frequency separation of the discrete modes. The
Kolmogorov-Zakharov energy cascade is then strongly altered and is frozen
before reaching the dissipative regime expected in the theory.Comment: accepted for publication in Physical Review
On role of symmetries in Kelvin wave turbulence
E.V. Kozik and B.V. Svistunov (KS) paper "Symmetries and Interaction
Coefficients of Kelvin waves", arXiv:1006.1789v1, [cond-mat.other] 9 Jun 2010,
contains a comment on paper "Symmetries and Interaction coefficients of Kelvin
waves", V. V. Lebedev and V. S. L'vov, arXiv:1005.4575, 25 May 2010. It relies
mainly on the KS text "Geometric Symmetries in Superfluid Vortex Dynamics}",
arXiv:1006.0506v1 [cond-mat.other] 2 Jun 2010. The main claim of KS is that a
symmetry argument prevents linear in wavenumber infrared asymptotics of the
interaction vertex and thereby implies locality of the Kelvin wave spectrum
previously obtained by these authors. In the present note we reply to their
arguments. We conclude that there is neither proof of locality nor any
refutation of the possibility of linear asymptotic behavior of interaction
vertices in the texts of KS
Turbulent thermalization of weakly coupled non-abelian plasmas
We study the dynamics of weakly coupled non-abelian plasmas within the
frameworks of classical-statistical lattice gauge-theory and kinetic theory. We
focus on a class of systems which are highly occupied, isotropic at all times
and initially characterized by a single momentum scale. These represent an
idealized version of the situation in relativistic heavy ion-collisions in the
color-glass condensate picture, where on a time scale after the
collision of heavy nuclei a longitudinally expanding plasma characterized by
the saturation scale is formed. Our results indicate that the system
evolves according to a turbulent Kolmogorov cascade in the classical regime.
Taking this into account, the kinetic description is able to reproduce
characteristic features of the evolution correctly.Comment: 8 pages, 6 figure
Differential approximation for Kelvin-wave turbulence
I present a nonlinear differential equation model (DAM) for the spectrum of
Kelvin waves on a thin vortex filament. This model preserves the original
scaling of the six-wave kinetic equation, its direct and inverse cascade
solutions, as well as the thermodynamic equilibrium spectra. Further, I extend
DAM to include the effect of sound radiation by Kelvin waves. I show that,
because of the phonon radiation, the turbulence spectrum ends at a maximum
frequency where
is the total energy injection rate, is the speed of sound and
is the quantum of circulation.Comment: Prepared of publication in JETP Letter
Energy and Vorticity Spectra in Turbulent Superfluid He from to
We discuss the energy and vorticity spectra of turbulent superfluid He in
all the temperature range from up to the phase transition "
point", K. Contrary to classical developed turbulence
in which there are only two typical scales, i.e. the energy injection and
the dissipation scales , here the quantization of vorticity introduces
two additional scales, i.e the vortex core radius and the mean vortex
spacing . We present these spectra for the super- and normal-fluid
components in the entire range of scales from to including the
cross-over scale where the hydrodynamic eddy-cascade is replaced by the
cascade of Kelvin waves on individual vortices. At this scale a bottleneck
accumulation of the energy was found earlier at .
We show that even very small mutual friction dramatically suppresses the
bottleneck effect due to the dissipation of the Kelvin waves. Using our results
for the spectra we estimate the Vinen "effective viscosity" in the
entire temperature range and show agreement with numerous experimental
observation for .Comment: 20 pages, 5 figure
Warm turbulence in the Boltzmann equation
We study the single-particle distributions of three-dimensional hard sphere
gas described by the Boltzmann equation. We focus on the steady homogeneous
isotropic solutions in thermodynamically open conditions, i.e. in the presence
of forcing and dissipation. We observe nonequilibrium steady state solution
characterized by a warm turbulence, that is an energy and particle cascade
superimposed on the Maxwell-Boltzmann distribution. We use a dimensional
analysis approach to relate the thermodynamic quantities of the steady state
with the characteristics of the forcing and dissipation terms. In particular,
we present an analytical prediction for the temperature of the system which we
show to be dependent only on the forcing and dissipative scales. Numerical
simulations of the Boltzmann equation support our analytical predictions.Comment: 4 pages, 5 figure
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