Development of special flow test rigs and their application for pulsating and transitional flow investigations [Elektronische Ressource] = Entwicklung spezieller Versuchseinrichtungen und deren Anwendung für pulsierende und transitionale Strömungsuntersuchungen / vorgelegt von Kais Elias Haddad

Sujets

• Physik

Informations

• Publié par: friedrich-alexander-universitat_erlangen-nurnberg
• Publié le: 01 janvier 2009
• Nombre de lectures: 20
• Langue: English
• Poids de l'ouvrage: 5 Mo

Extrait

Development of Special Flow Test Rigs and their
Application for Pulsating and Transitional Flow
Investigations

Entwicklung spezieller Versuchseinrichtungen und deren
Anwendung für pulsierende und transitionale
Strömungsuntersuchungen



Der Technischen Fakulität der
Friedrich-Alexander-Universität Erlangen Nürnberg


Zur Erlangung des Grades


DOKTOR - INGENIEUR


vorgelegt von


Kais Elias Haddad



Erlangen - 2009




























Als Dissertation genehmigt von der
Technischen Fakulität der
Universität Erlangen-Nürnberg



Tag der Einreichung: 24.11.2008
Tag Der Promotion: 03.02.2009
Dekan: Prof. Dr.-Ing. habil. Johannes Huber
Berichterstatter: Prof. i.R. Dr. Dr. h. c. Franz Durst
Prof. Dr.- Ing. Ahmed Al-Salaymeh


















To my mother, my father,
my sister and my brothers



Acknowledgments



During my research stay in Erlangen to carry out my PhD work, many people helped me to
finalize the thesis successfully. Furthermore, the conducted research could not have been
finished without the financial support that I received from DAAD which is gratefully
acknowledged.
In the first place, I would like to express my deep appreciation to my supervisor Prof. Dr.
Franz Durst for his continuous support and guidance. I want also to thank him because he
gave me the opportunity to perform the major part of my thesis in his company, FMP. Their, I
found the scientific environment which encouraged me to go further in my work. Through his
supervision, I developed my research abilities and I gained a valuable knowledge in the field
of fluid mechanics, moreover, I learned a lot from him.
I am also thankful to Dr.-Ing. Özgür Ertunc, the head of group, for the valuable discussions
and suggestions during different phases of my work.
Many thanks due to Dr. Ahmed Al-Salaymeh who encouraged and helped me to come to
LSTM-Erlangen to perform my research. During his frequent visits to the institute as a guest
researcher, I utilized a lot from his experience in fluid mechanics.
I appreciate also the help that I received from the LSTM mechanical and electrical workshop.
Hence I would like to thank Horst Weber, Rolf Zech, Franz Kaschak, Josef Sveida, Heinz
Hedwig, Jürgen Heubeck and Werner Sippl. Many thanks to Ina Paulus, Johanna Grasser for
the friendly administrative support.
I am very grateful to Dr. Osama Saleh, Dr.-Ing. Bülent Ünsal, Dipl.-Ing. Philip Epple, Dipl.-
Ing.Yousef Abu-Sharkh, and B.Sc Amra Mekic for helpful discussions and detailed
assistance. I would like to thank also Dr. M. Mishra who contributed to the analytical portion
of the work conducted in the field of pulsating flows.
I must say special thanks to my parents who graciously instilling in me the value of education
and supporting me throughout my education.

i


Abstract


The research work summarized in this thesis was carried out during the time the author
spent at the Institute of Fluid Mechanics of the Friedrich-Alexander-University of
Erlangen-Nürnberg and partially also in the Centre of Advanced Fluid Mechanics of FMP
Technology GmbH, the latter also being located in Erlangen. During this time, the author
was able to carry out research work in the field of pulsating channel and pipe flows in
general but he also performed investigations of the laminar-to-turbulent transition
occurring without pulsations. In the present thesis, the outcome of this research work is
summarized.
The studies on laminar pulsating channel and pipe flows show that at highly enough
dimensionless frequenciesF , reversal can happen far from the wall and the velocity profile
corresponding to that is characterized by two inflection points. However, all the previous
investigations suggested that reversal can happen only very close to the wall with one
inflection point. A reversal map was plotted to provide the conditions for both situations.
Properties such as reversal location and reversal duration were investigated also. The
obtained results indicated that the reversal occurred firstly near the wall, then with phase, it
travelled away till it reached a minimum value, after that the reversal location moved back
in the wall direction. Furthermore, it was found that reversal duration increased withF .
When comparing channel and pipe flows in terms of some parameters of technical
importance and for the same applied dimensionless frequency and mass flow rate
amplitudes, the obtained results indicated that pressure gradient, velocity and shear stress
dimensionless amplitudes are higher in the case of channel flow.
In the case of laminar pulsating channel flows with sinusoidal mass flow rate pulsations,
the analytical solution for the velocity profile was validated experimentally. Very good
agreement was obtained between the measured and calculated dimensionless velocity
*amplitudesu . A

iiThe author’s investigations on transitional pipe flows followed up the research carried out
by Dr.-Ing. Bülent Ünsal and Mina Nishi, B.Sc., M.Sc. and he utilized their test rig for
some of his first investigations. The research work they had carried out employing this test
rig, showed that the critical Reynolds numbers, where laminar-to-turbulent transitional
happens, increased with increasing pipe diameter. This finding agreed well with data
available in the literature. Partially understanding this behavior of pipe flow test rigs
yielded the design of a new test section to prove that flow equipment can be built where
the critical Reynolds number is inversely proportional to the pipe diameter. This is
elaborated on in the thesis and results of laminar-to turbulent measurements are shown to
demonstrate the above-mentioned behavior of flow transition.
The thesis also stresses that laminar-to-turbulent- transition in pipe flows can be caused by
an instability that relates to the entire test rig and not so much to the pipe flow itself. Of
course, the pipe flow is part of the test rig and there is a small influence but not of the
strong kind that the measured transition reported in the literature shows as a function of
Reynolds number.
It has been pointed out in the literature that hot-wire response depends on the mass flow
rate per unit area ()ρU rather than the local velocity U , but very convincing data covering
a wide range of flow densities, are not available. This triggered the author’s interest to
develop a test rig to calibrate hot wire with respect to ( ρU ) for density variations in the
3range1 − 7kg /m . The final results showed a slight pressure dependence of the calibration
function.
Based on the ()ρU -measurements and in order to determine important properties for gases
such as density, viscosity and thermal conductivity, a novel measurement system was
developed. The principle of the proposed system and its description are provided in the
thesis.
iii


Zusammenfassung


Die zusammengefasste Forschungsarbeit in dieser Dissertation wurde während der Zeit
durchgeführt, die der Autor am Institut für Strömunngsmechanik der Friedrich-Alexander-
Universität Erlangen-Nürnberg und teilweise auch am „Center of Advanced Fluid Mechanics
of FMP Technology GmbH“ tätig gewesen ist. Whärend dieser Zeit war der Autor in der Lage
sowohl Forschungsarbeiten im Bereich der pulsierenden Kanal-und Rohrströmung
durchzuführen aber auch auch Untersuchungen im Bereich des laminar-turbulenten
Übergangs ohne auftretender Pulsation. In der vorliegenden Dissertation sind die Ergebnisse
dieser Forschungsarbeiten zusammenfassend dargestellt.
Die Studien über laminar, pulsierender Kanal-und Rohrströmung zeigten dass bei hohen
genügend dimensionslosen FrequenzenF eine Strömungsumkehr weit entfernt von der Wand
auftreten kann. Das entsprechende Geschwindigkeitsprofil wird durch zwei Wendepunkte
charakterisiert. Alle vorherigen Untersuchungen schlagen hingegen vor, dass eine
Strömungsumkehr nur sehr nahe an der Wand mit lediglich einem Wendepunkt auftreten
kann. Zur Bestimmung der Parameter für beide Situationen wurde die Bedingungen für die
Strömungsumkehr in einem Diagramm graphisch dargestellt.
Es wurden ebenfalls Strömungseigenschaften, wie z. B. die Position für die Strömungsumkehr
und die Umkehrdauer quantitativ untersucht. Die erzielten Ergebnisse zeigten, dass die
Strömungsumkehr zunächst in der Nähe der Wand auftrat und sich mit Phase anschließend
weiter bewegte bis sie einen minimalen Wert erreicht. Danach bewegte sich die Position für
die Strömungsumkehr zurück in Richtung Wand. Darüber hinaus wurde