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@PHDTHESIS{Rietz:808409,
author = {Rietz, Manuel},
othercontributors = {Kneer, Reinhold and Scheid, Benoit},
title = {{D}ynamics of falling films under the influence of a
destabilizing body force},
school = {Rheinisch-Westfälische Technische Hochschule Aachen},
type = {Dissertation},
address = {Aachen},
reportid = {RWTH-2020-12044},
pages = {1 Online-Ressource (129 Seiten) : Illustrationen,
Diagramme},
year = {2020},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University 2021; Dissertation, Rheinisch-Westfälische
Technische Hochschule Aachen, 2020},
abstract = {A cascade of primary and secondary fluid dynamical
instabilities leads to complex patterns of waves on the
surface of falling liquid films. In falling films under the
influence of a destabilizing body force, the film surface
topology potentially evolves towards a distinct spanwise
structuring into rivulets, which might be accompanied by
fluid detachment from the substrate (dripping) depending on
the specific properties of the film flow. The presence of a
destabilizing body force, in this framework, encompasses all
configurations in which fluid is accelerated normal to a
bounding wall with the acceleration vector pointing from the
fluid to the surrounding atmosphere. This thesis provides
experimental as well as numerical data regarding the linear
and non-linear evolution of falling films under the
influence of a destabilizing body force with specific focus
on the interplay of primary and secondary instabilities and
long term structuring of the film surface. First, a software
implementation of state of the art weighted residual
boundary layer models for falling films is introduced. The
presented implementation allows to rapidly compute
three-dimensional wave patterns in falling films due to the
use of spectral methods and GPU-accelerated computing.
Subsequently, a comprehensive experimental study is
presented in which the evolution of a falling film on the
outside of a rotating cylinder is analyzed under variation
of imposed flow rates and rotation frequency. Correlations
are provided both for the wavelength as well as the
inception length of developing rivulet structures. Finally,
a numerical analysis of flow evolution, interaction of
primary and secondary instabilities of the film surface and
spanwise structuring before the dripping regime is performed
for the case of a film on the underside of an inclined wall.
In this context, simulations of the long term evolution of
the film flow in a large domain are enabled through the
application of the introduced software implementation of
relevant falling film models. In the end, through the
combination of experimental and numerical analysis, a
comprehensive overview of the evolution of falling films
under the influence of a destabilizing body force deep into
the non-linear regime is provided. Adding to this,
dependencies of characteristics of developing flow
structures on fluid properties and further system parameters
are given.},
cin = {412610},
ddc = {620},
cid = {$I:(DE-82)412610_20140620$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2020-12044},
url = {https://publications.rwth-aachen.de/record/808409},
}
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