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@PHDTHESIS{Denker:811229,
author = {Denker, Dominik},
othercontributors = {Pitsch, Heinz and Attili, Antonio},
title = {{G}radient trajectory analysis of reacting turbulent flows},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Düren},
publisher = {Shaker Verlag},
reportid = {RWTH-2021-01043},
isbn = {978-3-8440-7739-1},
series = {Berichte aus der Strömungstechnik},
pages = {Online-Ressource (xix, 151 Seiten) : Illustrationen,
Diagramme},
year = {2020},
note = {Druckausgabe: 2020. - Auch veröffentlicht auf dem
Publikationsserver der RWTH Aachen University 2021;
Dissertation, RWTH Aachen University, 2020},
abstract = {In this thesis, reacting turbulent flows are analyzed from
a structural point of view using Dissipation Element (DE)
analysis, which is a gradient trajec- tory (GT) based method
for compartmentalizing turbulent fields into space filling
sub-regions in which scalars behave monotonically. In the
context of combustion, this property is important, as DEs
locally and unambiguously indicate the maximum extent a
diffusive transport dominated structure, such as a flame,
can potentially occupy in a turbulent flow. First, DE
analysis is applied to the mixture fraction field Z of a
series of direct numerical simulations (DNS) of non-premixed
jet flames. In a statistical investigation, it is shown that
the normalized DE parameter statistics as well as the
characteristic scalings of the respective mean quantities do
not differ from non-reacting turbulent flows and are
therefore unaffected by the heat release. Additionally, it
is demonstrated that the scalar dissipation rate χ can be
related to the gradient of the larger local flow topology as
represented by the DE gradient g. The DE parameters are then
used in the construction of a regime diagram for
non-premixed combustion which is verified by the DNS
results. Secondly, non-local effects in DNS of premixed
combustion are investigated in a series of spatially
evolving jet flames. DE analysis is applied to the
temperature fields T which, contrary to Z, possess a
chemical source term. The self-similarity of the normalized
DE length distribution is retained, but the statistics of
the scalar difference ∆T show a clear influence of the
flame structure. In the consecutive GT based flame structure
analysis, it is shown that the introduction of extremal
points close to the flame front leads to a significant
thickening of both the preheating and inner reaction zone.
This effect is quantified and related to the turbulent
burning velocity. Finally, the insights gained are used in
combustion modelling. The scaling and self-similarity of the
DE parameter statistics are used in a framework for the
prediction of combustion regimes in non-premixed combustion.
This framework is applied in the Reynolds averaged
Navier-Stokes simulation of a passenger car diesel engine.
Further, a novel model for the probability density function
of Z is presented, which considers effects of laminar
regions and external intermittency.},
cin = {411410},
ddc = {620},
cid = {$I:(DE-82)411410_20140620$},
pnm = {REGIMES IN TURBULENT NON-PREMIXED COMBUSTION
$(jhpc22_20150501)$ / MILESTONE - Multi-Scale Description of
Non-Universal Behavior in Turbulent Combustion (695747) /
Direct Numerical Simulation and Modeling of Oxy-Fuel
Combustion $(jhpc22_20180501)$},
pid = {$G:(DE-Juel1)jhpc22_20150501$ / G:(EU-Grant)695747 /
$G:(DE-Juel1)jhpc22_20180501$},
typ = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
doi = {10.18154/RWTH-2021-01043},
url = {https://publications.rwth-aachen.de/record/811229},
}
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