Design of an endoscopic 3-D particle-tracking velocimetry system and its application in flow measurements within a gravel layer [Elektronische Ressource] / presented by Michael Klar

Informations

• Publié par: ruprecht-karls-universitat_heidelberg
• Publié le: 01 janvier 2005
• Nombre de lectures: 27
• Langue: Deutsch
• Poids de l'ouvrage: 7 Mo

Extrait

Dissertation
submitted to the
Combined Faculties for the Natural Sciences and for Mathematics
of the Ruperto-Carola University of Heidelberg, Germany
for the degree of
Doctor of Natural Sciences
presented by
Diplom-Physicist Michael Klar,
born in Heilbronn.
Date of oral examination: 30.11.2005.Design of an endoscopic
3-D Particle-Tracking Velocimetry system
and its application in ow measurements
within a gravel layer
¤Referees: Prof. Dr. Bernd Jahne
Prof. Dr. Kurt RothZusammenfassung
In der vorliegenden Arbeit wird eine neuartige Technik zur Messung von dreidimensionalen Stromungen¤
¤ ¤in einem porosen Medium vorgestellt, die erstmals den experimentellen Zugang zur Porenstromung in
einer Kiessohle erlaubt. Zwei faseroptische Endoskope werden in stereoskopischer Anordnung eingesetzt,
um Bildsequenzen des Stromungsfeldes¤ innerhalb einer einzelnen Kiespore zu gewinnen. Zur Auswert-
ung der Bilddaten wird die 3-D Particle-Tracking Velocimetry (3-D PTV) verwendet. Diese ermoglicht¤
die dreidimensionale Rekonstruktion Lagrange’scher Partikeltrajektorien. Die zugrundeliegenden Bildver-
arbeitungsverfahren werden entscheidend weiterentwickelt und an die speziellen Verhaltnisse¤ endoskop-
ischer Bildgewinnung angepasst. Dies beinhaltet Methoden zur Bildvorverarbeitung, zur robusten Kamera-
kalibrierung, zur Bildsegmentierung sowie zur Partikelverfolgung. Nach einer Leistungs- und Genauigkeits-
analyse wird das Messverfahren in umfangreichen systematischen Untersuchungen der Stromung¤ durch
eine Kiessohle in einer Versuchsrinne der Bundesanstalt fur¤ Wasserbau in Karlsruhe eingesetzt. Ein erweit-
erter experimenteller Aufbau ermoglicht¤ neben der Messung der Porenstromung¤ in drei Poren die simul-
tane Erfassung des sohlnahen 3-D Stromungsfelds¤ in der turbulenten Kanalstromung¤ oberhalb der Kies-
sohle sowie von Kornbewegungen in einer Sandschicht unterhalb der Kiessohle. Somit kann erstmals die
Interaktion der Ober achenstr¤ omung¤ mit der Stromung¤ im Porenraum zeitlich und raumlich¤ hoch aufgelost¤
untersucht werden. Die experimentellen Untersuchungen sind Teil eines internationalen Forschungspro-
jekts des Filter And Erosion Research Clubs (FERC). Das langfristige Ziel dieses Projekts ist es, den Ein-
uss turbulenter Geschwindigkeits- und Druckschwankungen auf die Sohlstabilitat¤ von Wasserstrassen zu
quanti zieren. Die gewonnenen Messdaten ermoglichen¤ neue Einblicke in das Dampfungsv¤ erhalten einer
Kiessohle und konnen¤ zukunftig¤ zum Vergleich mit numerischen, analytischen und phanomenologischen¤
Modellen herangezogen werden.
Abstract
In this thesis a novel method for 3-D ow measurements within a permeable gravel layer is developed.
Two beroptic endoscopes are used in a stereoscopic arrangement to acquire image sequences of the ow
eld within a single gravel pore. The images are processed by a 3-D Particle-Tracking Velocimetry (3-D
PTV) algorithm, which yields the three-dimensional reconstruction of Lagrangian particle trajectories. The
underlying image processing algorithms are signi cantly enhanced and adapted to the special conditions
of endoscopic imagery. This includes methods for image preprocessing, robust camera calibration, image
segmentation and particle-tracking. After a performance and accuracy analysis, the measurement technique
is applied in extensive systematic investigations of the ow within a gravel layer in an experimental ume at
the Federal Waterways Engineering and Research Institute in Karlsruhe. In addition to measurements of the
pore ow within three gravel pores, an extended experimental setup enables the simultaneous observation of
the near-bed 3-D ow eld in the turbulent open-channel ow above the gravel layer and of grain motions
in a sand layer beneath the gravel layer. The interaction of the free surface ow and the pore ow can be
analyzed for the rst time with a high temporal and spatial resolution. The experiments are part of a research
project initiated by an international cooperation called Filter and Erosion Research Club (FERC). The long-
term goal of this project is to quantify the in uence of turbulent velocity and pressure uctuations on the
bed stability of waterways. The obtained experimental data provide new insight into the damping behaviour
of a gravel bed and can be used for comparison with numerical, analytical and phenomenological models.(...) We had made many similar journeys together, but the Danube, more than any other river
I knew, impressed us from the very beginning with its aliveness. From its tiny bubbling entry
into the world among the pinewood gardens of Donaueschingen, until this moment when it
began to play the great river-game of losing itself among the deserted swamps, unobserved,
unrestrained, it had seemed to us like following the grown of some living creature. Sleepy at
rst, but later developing violent desires as it became conscious of its deep soul, it rolled, like
some huge uid being, through all the countries we had passed, holding our little craft on its
mighty shoulders, playing roughly with us sometimes, yet always friendly and well-meaning,
till at length we had come inevitably to regard it as a Great Personage. How, indeed, could it be
otherwise, since it told us so much of its secret life? At night we heard it singing to the moon as
we lay in our tent, uttering that odd sibilant note peculiar to itself and said to be caused by the
rapid tearing of the pebbles along its bed, so great is its hurrying speed. We knew, too, the voice
of its gurgling whirlpools, suddenly bubbling up on a surface previously quite calm; the roar of
its shallows and swift rapids; its constant steady thundering below all mere surface sounds; and
that ceaseless tearing of its icy waters at the banks. How it stood up and shouted when the rains
fell at upon its face! And how its laughter roared out when the wind blew upstream and tried
to stop its growing speed! (...)
ALGERNON BLACKWOOD, THE WILLOWS (1907)
The subject of the ow of uids, and particularly of water, fascinates everybody. We can all
remember, as children, playing in the bathtub or in mud puddles with the strange stuff. As we
get older, we watch streams, waterfalls, and whirlpools, and we are fascinated by this substance
which seems almost alive relative to solids. The behaviour of uids is in many ways very
unexpected and interesting (...). The efforts of a child trying to dam a small stream owing in
the street and his surprise at the strange way the water works its way out has its analog in our
attempts over the years to understand the ow of uids. We have tried to dam the water up -
in our understanding - by getting the laws and the equations that describe the ow. We will
describe these attempts in this chapter. In the next chapter, we will the unique way in
which water has broken through the dam and escaped our attempts to understand it.
RICHARD P. FEYNMAN, THE FEYNMAN LECTURES ON PHYSICS (1964)Contents
1 Introduction 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.1 Flow over and through permeable walls . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.2 River bed stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Related work and own contribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2.1 Work within the Filter and Erosion Research Club . . . . . . . . . . . . . . . . . . 5
1.2.2 Related experimental approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2.3 Own contribution and objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3 Thesis outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
I Foundations 11
2 Hydrodynamic background 13
2.1 Newtonian uids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.2 Flow of uids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.1 Basic equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.2 Nondimensional parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.3 Basic types of ow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3 Description of uid ow elds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.4 Turbulence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.4.1 Shear ow instability and transition to turbulence . . . . . . . . . . . . . . . . . . . 18
2.4.2 Statistical approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.5 Open-channel ow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.5.1 Basic equations and parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.5.2 In uence of rough walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.5.3 Coherent structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.5.4 Turbulence over rough beds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.6 Flow in porous media . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
i2.6.1 Basic equations and parameters . . . . . . . . . .