Ursescu, Ana (2005)
Channel flow of electrorheological fluids under an inhomogeneous electric field.
Technische Universität Darmstadt
Dissertation, Erstveröffentlichung
Kurzbeschreibung (Abstract)
This thesis is a theoretical study of the steady pressure driven channel flow of electrorheological fluids (ERF) under a space dependent electric field generated by finite electrodes. Chapter 1 consists in a general description of ERF and their engineering applications and presents also the motivation, the goal and the borders of this work. Chapter 2 summarizes the governing equations of electrorheology with the corresponding jump conditions. It is assumed that the flow does not affect the electric field and consequently, the electrical problem is decoupled from the mechanical one. Both electrical and mechanical boundary value problems are formulated for various configurations of finite electrodes with different potentials placed along the channel walls. The simple case of two infinite electrodes which generate a homogeneous electric field is solved analytically. In Chapter 3 analytical solutions for different mixed boundary value problems arising from the electrical problem formulated in Chapter 2 are found by use of the Wiener-Hopf method. The solutions are given in terms of infinite series involving Gamma functions. The results can be used to describe the electric field generated between two infinite grounded electrodes by either one long electrode or two long electrodes charged in an anti-symmetric or a non-symmetric way. The electric field in the vicinity of the electrode edges is asymptotically evaluated. Some parametric studies are made with respect to the ratio between the permittivity of the electrorheological fluid and the permittivity of the isolating material outside the channel. We compare the analytical with numerical solutions and find good agreement which is considered as a validation of the numerical method. Chapter 4 treats the mechanical problem in more detail. First a review of the constitutive models used to describe the ER-fluids in the literature is given. Then two-dimensional alternative constitutive laws appropriate for numerical simulations originating from the Casson-like and power law models are introduced using a parameter. In the end we non-dimensionalize the problem in both cases. In the last Chapter, we simulate numerically the flow of the Rheobay TP AI 3565 ER-fluid using the alternative Casson-like model and the EPS 3301 ER-fluid using the alternative power-law model by applying a finite element program. The behaviour of different fields such as velocity, pressure, generalized viscosity and the second invariant of the strain rate tensor near the electrode edges is studied for both fluids. A comparison with the experimental data is performed, validating the simulations. In order to investigate how the numerical solution depends on the constitutive model we perform a parallel analysis of the two rheological models by applying them to the same material (Rheobay). Then we optimize the configuration of the electrodes by using the inhomogeneities caused by the end effects of the electrodes in order to obtain an enhancement of the ER-effect.
Typ des Eintrags: | Dissertation | ||||
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Erschienen: | 2005 | ||||
Autor(en): | Ursescu, Ana | ||||
Art des Eintrags: | Erstveröffentlichung | ||||
Titel: | Channel flow of electrorheological fluids under an inhomogeneous electric field | ||||
Sprache: | Englisch | ||||
Referenten: | Hutter, PhD Kolumban ; Ruzicka, Prof. Dr. Michael | ||||
Berater: | Hutter, Prof. PhD Kolumban | ||||
Publikationsjahr: | 10 Mai 2005 | ||||
Ort: | Darmstadt | ||||
Verlag: | Technische Universität | ||||
Datum der mündlichen Prüfung: | 21 Januar 2005 | ||||
URL / URN: | urn:nbn:de:tuda-tuprints-5564 | ||||
Kurzbeschreibung (Abstract): | This thesis is a theoretical study of the steady pressure driven channel flow of electrorheological fluids (ERF) under a space dependent electric field generated by finite electrodes. Chapter 1 consists in a general description of ERF and their engineering applications and presents also the motivation, the goal and the borders of this work. Chapter 2 summarizes the governing equations of electrorheology with the corresponding jump conditions. It is assumed that the flow does not affect the electric field and consequently, the electrical problem is decoupled from the mechanical one. Both electrical and mechanical boundary value problems are formulated for various configurations of finite electrodes with different potentials placed along the channel walls. The simple case of two infinite electrodes which generate a homogeneous electric field is solved analytically. In Chapter 3 analytical solutions for different mixed boundary value problems arising from the electrical problem formulated in Chapter 2 are found by use of the Wiener-Hopf method. The solutions are given in terms of infinite series involving Gamma functions. The results can be used to describe the electric field generated between two infinite grounded electrodes by either one long electrode or two long electrodes charged in an anti-symmetric or a non-symmetric way. The electric field in the vicinity of the electrode edges is asymptotically evaluated. Some parametric studies are made with respect to the ratio between the permittivity of the electrorheological fluid and the permittivity of the isolating material outside the channel. We compare the analytical with numerical solutions and find good agreement which is considered as a validation of the numerical method. Chapter 4 treats the mechanical problem in more detail. First a review of the constitutive models used to describe the ER-fluids in the literature is given. Then two-dimensional alternative constitutive laws appropriate for numerical simulations originating from the Casson-like and power law models are introduced using a parameter. In the end we non-dimensionalize the problem in both cases. In the last Chapter, we simulate numerically the flow of the Rheobay TP AI 3565 ER-fluid using the alternative Casson-like model and the EPS 3301 ER-fluid using the alternative power-law model by applying a finite element program. The behaviour of different fields such as velocity, pressure, generalized viscosity and the second invariant of the strain rate tensor near the electrode edges is studied for both fluids. A comparison with the experimental data is performed, validating the simulations. In order to investigate how the numerical solution depends on the constitutive model we perform a parallel analysis of the two rheological models by applying them to the same material (Rheobay). Then we optimize the configuration of the electrodes by using the inhomogeneities caused by the end effects of the electrodes in order to obtain an enhancement of the ER-effect. |
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Alternatives oder übersetztes Abstract: |
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Freie Schlagworte: | elektrorheologische Flüssigkeiten, endliche Elektroden | ||||
Schlagworte: |
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Fachbereich(e)/-gebiet(e): | Studienbereiche Studienbereiche > Studienbereich Mechanik |
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Hinterlegungsdatum: | 17 Okt 2008 09:22 | ||||
Letzte Änderung: | 26 Aug 2018 21:25 | ||||
PPN: | |||||
Referenten: | Hutter, PhD Kolumban ; Ruzicka, Prof. Dr. Michael | ||||
Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: | 21 Januar 2005 | ||||
Schlagworte: |
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