2,758 research outputs found
Multiplier phenomenology in random multiplicative cascade processes
We demonstrate that the correlations observed in conditioned multiplier
distributions of the energy dissipation in fully developed turbulence can be
understood as an unavoidable artefact of the observation procedure. Taking the
latter into account, all reported properties of both unconditioned and
conditioned multiplier distributions can be reproduced by cascade models with
uncorrelated random weights if their bivariate splitting function is non-energy
conserving. For the alpha-model we show that the simulated multiplier
distributions converge to a limiting form, which is very close to the
experimentally observed one. If random translations of the observation window
are accounted for, also the subtle effects found in conditioned multiplier
distributions are precisely reproduced.Comment: 4 pages, 3 figure
Cumulant ratios in fully developed turbulence
In the context of random multiplicative cascade processes, we derive
analytical solutions for one- and two-point cumulants with restored
translational invariance. On taking ratios of cumulants in ln epsilon,
geometrical effects due to spatial averaging cancel out. These ratios can
successfully distinguish between splitting functions while multifractal scaling
exponents and multiplier distributions cannot.Comment: 9th Workshop on Multiparticle Production (Torino), 9 pages latex,
incl 9 figs and espcrc2.st
Analytic multivariate generating function for random multiplicative cascade processes
We have found an analytic expression for the multivariate generating function
governing all n-point statistics of random multiplicative cascade processes.
The variable appropriate for this generating function is the logarithm of the
energy density, ln epsilon, rather than epsilon itself. All cumulant statistics
become sums over derivatives of ``branching generating functions'' which are
Laplace transforms of the splitting functions and completely determine the
cascade process. We show that the branching generating function is a
generalization of the multifractal mass exponents. Two simple models from fully
developed turbulence illustrate the new formalism.Comment: REVTeX, 4 pages, 2 PostScript figs, submitted to PR
The Markovian metamorphosis of a simple turbulent cascade model
Markovian properties of a discrete random multiplicative cascade model of
log-normal type are discussed. After taking small-scale resummation and
breaking of the ultrametric hierarchy into account, qualitative agreement with
Kramers-Moyal coefficients, recently deduced from a fully developed turbulent
flow, is achieved.Comment: 6 pages, 2 figure
Prospects for parity-nonconservation experiments with highly charged heavy ions
We discuss the prospects for parity-nonconservation experiments with highly charged heavy ions. Energy levels and parity mixing for heavy ions with 2–5 electrons are calculated. We investigate two-photon transitions and the possibility of observing interference effects between weak-matrix elements and Stark matrix elements for periodic electric field configurations
Validation of Danish wind time series from a new global renewable energy atlas for energy system analysis
We present a new high-resolution global renewable energy atlas ({REatlas})
that can be used to calculate customised hourly time series of wind and solar
PV power generation. In this paper, the atlas is applied to produce
32-year-long hourly model wind power time series for Denmark for each
historical and future year between 1980 and 2035. These are calibrated and
validated against real production data from the period 2000 to 2010. The high
number of years allows us to discuss how the characteristics of Danish wind
power generation varies between individual weather years. As an example, the
annual energy production is found to vary by from the average.
Furthermore, we show how the production pattern change as small onshore
turbines are gradually replaced by large onshore and offshore turbines.
Finally, we compare our wind power time series for 2020 to corresponding data
from a handful of Danish energy system models. The aim is to illustrate how
current differences in model wind may result in significant differences in
technical and economical model predictions. These include up to
differences in installed capacity and differences in system reserve
requirements
Translationally invariant cumulants in energy cascade models of turbulence
In the context of random multiplicative energy cascade processes, we derive
analytical expressions for translationally invariant one- and two-point
cumulants in logarithmic field amplitudes. Such cumulants make it possible to
distinguish between hitherto equally successful cascade generator models and
hence supplement lowest-order multifractal scaling exponents and multiplier
distributions.Comment: 11 pages, 3 figs, elsart.cls include
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