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@PHDTHESIS{Hasenbeck:569681,
author = {Hasenbeck, Felix},
othercontributors = {Kull, Hans-Jörg and Reiter, Detlev},
title = {{D}evelopment and application of a multiscale model for the
magnetic fusion edge plasma region},
volume = {307},
school = {RWTH Aachen},
type = {Dissertation},
address = {Jülich},
publisher = {Forschungszentrum Jülich GmbH, Zentralbibliothek, Verlag},
reportid = {RWTH-2016-01338},
isbn = {978-3-95806-120-0},
series = {Schriften des Forschungszentrums Jülich. Reihe Energie
$\&$ Umwelt},
pages = {188 Seiten : Illustrationen, Diagramme},
year = {2016},
note = {Druckausgabe: 2016. - Onlineausgabe: 2016. - Auch
veröffentlicht auf dem Publikationsserver der RWTH Aachen
University; Dissertation, RWTH Aachen, 2015},
abstract = {Plasma edge particle and energy transport perpendicular to
the magnetic field plays a decisive role for the performance
and lifetime of a magnetic fusion reactor. For the
particles, classical and neoclassical theories underestimate
the associated radial transport by at least an order of
magnitude. Drift fluid models, including mesoscale processes
on scales down to tenths of millimeters and microseconds,
account for the experimentally found level of radial
transport; however, numerical simulations for typical
reactor scales (of the order of seconds and centimeters) are
computationally very expensive. Large scale code simulations
are less costly but usually lack an adequate model for the
radial transport.The multiscale model presented in this work
aims at improving the description of radial particle
transport in large scale codes by including the effects of
averaged local drift fluid dynamics on the macroscale
profiles. The multiscale balances are derived from a generic
multiscale model for a fluid, using the Braginskii closure
for a collisional, magnetized plasma, and the assumptions of
the B2 code model (macroscale balances) and the model of the
local version of the drift fluid code ATTEMPT (mesoscale
balances). A combined concurrent-sequential coupling
procedure is developed for the implementation of the
multiscale model within a coupled code system. An algorithm
for the determination of statistically stationary states and
adequate averaging intervals for the mesoscale data is
outlined and tested, proving that it works consistently and
efficiently.The general relation between mesoscale and
macroscale dynamics is investigated exemplarily by means of
a passive scalar system. While mesoscale processes are
convective in this system, earlier studies for small Kubo
numbers K 1 have shown that the macroscale behavior is
diffusive. In this work it is demonstrated by numerical
experiments that also in the regime of large Kubo numbers K
1 the macroscale transport remains diffusive. An analytic
expression for the diffusion coefficient D is found, being
consistent with results from percolation theory.The
multiscale model and the coupling procedure are benchmarked
with a one-dimensional test problem which consists of
coupling the local version of the drift fluid code ATTEMPT
to a 1D macroscale code to determine the time-dependent
evolution of the flux surface averaged density in radial
direction in the tokamak edge region. The reference
simulation is given by a simulation of the non-local version
of ATTEMPT, accounting for both the mesoscale and the
macroscale evolution. Results of the coupled code
simulations show that the macroscale evolution of the
density and the radial particle flux can be reproduced with
typical uncertainties of 6 and $22\%,$ respectively. Time
savings with respect to the non-local simulations are of a
factor of ten for a typical macroscale evolution time of 10
milliseconds while a speedup factor of the order of 50 is
achievable for an edge region with a radial extent of ~ 30
cm and typical radial profile lengths of ~ 5 cm.The
multiscale model for two-dimensional, stationary problems is
realized by coupling of the B2 code and the local version of
the ATTEMPT code. The results of the corresponding coupled
code simulations for experiments at the tokamak TEXTOR
provide plasma profiles in agreement with experimental
measurements with uncertainties regarding the electron
density and electron temperature measured at the outer
midplane around 10 to $25\%.$ Poloidally and radially
dependent profiles of the radial particle diffusion
coefficients D, self-consistently determined by B2-ATTEMPT,
have typical values of 0.3 to 0.9 $m^2/s$ and are within a
10 to $30\%$ range of effective diffusion coefficients
employed in B2-EIRENE simulations to fit simulation results
to measured density profiles. The poloidal dependence of D
as given by the B2-ATTEMPT simulations accounts for the
experimentally confirmed ballooning character of radial
transport with D at the low field side, being up to a factor
two larger than on the high field side.},
cin = {135110 / 135220 / 130000},
ddc = {530},
cid = {$I:(DE-82)135110_20140620$ / $I:(DE-82)135220_20140620$ /
$I:(DE-82)130000_20140620$},
typ = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
urn = {urn:nbn:de:hbz:82-rwth-2016-013380},
url = {https://publications.rwth-aachen.de/record/569681},
}
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