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@PHDTHESIS{Nierhaus:51363,
author = {Nierhaus, Thomas},
othercontributors = {Schröder, Wolfgang},
title = {{M}odeling and simulation of dispersed two-phase flow
transport phenomena in electrochemical processes},
address = {Aachen},
publisher = {Publikationsserver der RWTH Aachen University},
reportid = {RWTH-CONV-113664},
pages = {XXII, 172 S. : Ill., graph. Darst.},
year = {2009},
note = {Zsfassung in dt. u. engl. Sprache. -
Cotutelle-Dissertation; Aachen, Techn. Hochsch., Diss.,
2009. - Vrije Universiteit Brussel, Diss. 2009},
abstract = {Modeling the physics of two-phase flows and the development
of numerical tools for their simulation are important
challenges in modern CFD. Contrary to single-phase flows,
where the underlying physics is quite well understood and
relatively general numerical methods can be employed in flow
simulations, the physical phenomena occurring in two-phase
flows are far more versatile and still not fundamentally
understood in all details. The difficulties in multiphase
flow modeling arise from large dissimilarities between
different types of flow configurations and the complex flow
conditions associated. Various modeling approaches and
numerical methods have been derived and applied in this
scope during the last decades. This process lead to the
conclusion that the applicability of a particular modeling
approach strongly depends on the type of two-phase flow
configuration involved. In other words, to pick an adequate
numerical approach to simulate a particular two-phase flow
problem on a computer, it is required to carefully identify
the underlying physics before selecting a solution method.
This Ph.D. thesis deals with modeling and simulation of
dispersed two phase flows. Such flows involve a continuous
carrier medium that contains small dispersed particles or
bubbles. In terms of material properties and states of
matter involved, gaseous flows involving solid particles
differ significantly from liquid flows involving gas
bubbles. However, if we regard the physical topologies of
these two types of two-phase flow, we see that there are
also very high similarities. In dispersed flows, the
secondary phase is scattered into small entities in a
continuous primary phase flow. The phase interfaces in
dispersed two-phase flows are very small compared to the the
global scale of the flow problem of interest. These
circumstances lead to the conclusion that dispersed
two-phase flows, regardless of their physical parameters,
can generally be treated by a unified modeling approach,
where only the modeling parameters distinguish the sub-type
of the flow, may it be of particle-laden or bubbly nature. A
promising model to provide a numerical solution to
incorporate different types of dispersed two-phase flows is
the Eulerian-Lagrangian approach. In the present work, the
development of an integrated numerical tool for the
simulation of particle-laden and bubbly two-phase flows
based on this approach is documented. The large similarities
but also the differences between particle-laden and bubbly
flows are identified and taken into account in the
simulations carried out in the scope of this work. Various
simulation examples to validate the simulation software are
given for both flow sub-types. A further challenge in
nowadays CFD is the integration of combined simulation
approaches that allow to track different physical and even
chemical mechanisms. A frequently referred key word
concerning such ambitious intentions is {it multi-physics}.
A topical numerical application of a multi-physical problem
is the combination of dispersed two-phase flow with
electrochemical phenomena such as ion transport and reaction
kinetics. In nowadays literature, broad spectra of models
exist to simulate two-phase flow and electrochemistry
separately, while an integrated approach taking into account
the coupling and interaction of both phenomena has not been
addressed in great detail so far. In the present Ph.D.
thesis, an approach for the numerical modeling of bubbly
two-phase flow combined with ion transport and gas-producing
electrochemical reactions is carried out. The fluid flow
part of the problem is addressed by the Eulerian-Lagrangian
approach while the electrochemistry is taken into account by
the Multi Ion Transport and Reaction Model (MITReM). An
integrated numerical method combining those two building
blocks allows to take into account coupling effects, such as
the influence of the gas phase on the conductivity of a
liquid electrolyte and the current density field as well as
the conversion of a gas flux into a set of bubbles on a
gas-producing electrode. This approach is found promising
and comprises a set of novelties regarding multi-physics
simulations.},
keywords = {Numerische Strömungssimulation (SWD) / Dispersion (SWD) /
Partikel (SWD) / Blasen (SWD) / Elektrochemie (SWD)},
cin = {415110},
ddc = {620},
cid = {$I:(DE-82)415110_20140620$},
typ = {PUB:(DE-HGF)11},
urn = {urn:nbn:de:hbz:82-opus-30013},
url = {https://publications.rwth-aachen.de/record/51363},
}
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