Investigation Of High Reynolds Number Pipe Flow
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| Author | : Franziska König |
| Publisher | : Cuvillier Verlag |
| Total Pages | : 164 |
| Release | : 2015-07-21 |
| Genre | : Technology & Engineering |
| ISBN | : 3736980493 |
Untersuchungen an Rohrströmungen bei hohen Reynoldszahlen sind bis heute eine große Herausforderung aufgrund der komplexen Mechanismen, die innerhalb turbulenter Rohrströmung auftreten. Daher ist es notwendig geeignete Experimente zu etablieren, um turbulente dynamische Prozesse aufzulösen und somit das Wissen zur Verfügung zu stellen, diese vollständig zu verstehen. Aufgrund dessen beschäftigt sich die vorliegende Dissertation mit der Konzeptionierung und dem Aufbau eines neuen Rohrwindkanals mit dem Fokus auf hohen Reynoldszahlen. Außerdem umfasst diese Arbeit erste experimentelle Untersuchungen und Ergebnisse. Diese zeigen, dass die neu konzipierte und aufgebaute Anlage geeignet ist, um eben diese Untersuchungen zur Turbulenz durchzuführen. Diese Aussage kann anhand intensiver Studien zum Verhalten der Einlauflange in Rohrströmungen bei verschiedenen Randbedingungen bestätigt werden. Weiterführende Experimente zur Bestimmung der Wandschubspannung unter Einbeziehung verschiedener Methoden haben gezeigt, dass an dieser Stelle große Schwierigkeiten und damit Abweichungen der Ergebnisse auftreten. Das wiederum spiegelt sich direkt im Skalierungsverhalten der Hauptströmungs- und Schwankungsgeschwindigkeit wieder. Neben der Einführung der neuen CoLaPipe und der Diskussion der ersten Ergebnisse beinhaltet diese Dissertation eine umfassende Literaturrecherche.
| Author | : Franziska König |
| Publisher | : |
| Total Pages | : 142 |
| Release | : 2016-03 |
| Genre | : |
| ISBN | : 9783736990494 |
| Author | : Zeinab Hallol |
| Publisher | : Cuvillier Verlag |
| Total Pages | : 146 |
| Release | : 2021-10-26 |
| Genre | : Technology & Engineering |
| ISBN | : 373696501X |
In this thesis, coherent turbulent structures in turbulent pipe flow are investigated at relatively high Reynolds numbers and study their association in both total kinetic energy and Reynolds shear stress. Experimental investigations have been performed in Cottbus Large Pipe test facility (CoLaPipe) for pipe flow over a wide range of Reynolds number 8 × 104 ≤ ReD ≤ 1 × 106, located at the Aerodynamics and Fluid Mechanics Department, Brandenburg University of Technology Cottbus- Senftenberg (BTU). The first part of the thesis focuses on determining the contribution of the coherent structures using one-dimensional spectral analysis and assessing the structures behaviour in the outer region of pipe flow using high spatial resolution Hot-wire measurement up to 30kHz. The results of the power and pre-multiplied spectrum of stream-wise velocity indicate that the wavelength value of very large scale motions (VLSMs) acquires 19R at a maximum Reynolds number range ReD=1 × 106 (Reτ =19000). On the other hand, large-scale motions have a wavelength value of 3R over different Reynolds number range. Regarding the identified wavelength values, it is observed that contribution to energy for structures greater than 3R carries 55% of total kinetic energy. In addition, temporal-spatial resolution using the High-speed PIV measurements has been performed in CoLaPipe to estimate the contribution magnitude of stream-wise/wall-normal velocity fluctuations to total kinetic energy and Reynolds shear stress in the logarithmic and outer layer.
| Author | : Mina Nishi |
| Publisher | : Sudwestdeutscher Verlag Fur Hochschulschriften AG |
| Total Pages | : 132 |
| Release | : 2009-08 |
| Genre | : |
| ISBN | : 9783838103181 |
A classical problem in fluid mechanics, laminar to turbulent transition in pipe flow, was investigated. Transition in pipe flow was first studied in detail by Reynolds (1883) and continued subsequently by numerous researchers. Nevertheless, there are still number of unknown issues that need clarification. As is well known, two distinct types of flow structure exist during a laminar to turbulent transition in pipes, namely puffs and slugs, termed by Wygnanski (1973). Investigations described in this dissertation were concentrated in the development of puffs and slugs in a pipe at different Reynolds numbers, following some preliminary research works. Also considered is a transformation from puffs to slugs through puff splittings, occurring while they propagate in a pipe or by an increase in Reynolds number. In low Reynolds number pipe flows, a dissipation of puffs was observed and then investigated. The time between when puffs were created and dissipated was termed `full- lifetime' and measured directly by a pressure transient. According to the investigations, possible evolutions of puffs were found and discussed.
| Author | : Russell J. Donnelly |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 483 |
| Release | : 2012-12-06 |
| Genre | : Science |
| ISBN | : 1461222303 |
Scientists have learned to use liquid and gaseous helium to overcome the limitations imposed by the usual wind and water tunnels for testing the performance of aircraft or the behavior of the atmosphere. This book covers fundamental studies of the turbulence problem, practical applications of turbulence, superfluid turbulence, cryogenic turbulence research, and new types of miniature flow instrumentation, all which are crucial for high Reynolds number research. This state-of-the-art presentation will interest physicists in fluid dynamics, engineers working with turbulent flows, and naval and aerospace engineers testing realistic parameter ranges.
| Author | : James Mueller Robertson |
| Publisher | : |
| Total Pages | : 144 |
| Release | : 1965 |
| Genre | : Fluid dynamics |
| ISBN | : |
The considerable literature on turbulent flow past rough surfaces is correlated in terms of modes of presenting the smooth-to-rough transition and the influences of roughness density and shape. Flow measurements in a 3 in. smooth and sand roughened pipe and in an 8 in. steel pipe with 'natural' roughness are reported. The temporal-mean velocity and friction measurements show transitional (between smooth and fully rough behavior) variations. The pipe factor variation is also elucidated; the sand-roughened pipe studies indicate a shift in Nikuradse's presentation. The turbulence - as intensity divided by shear velocity and macroscale in ratio to pipe radius - in rough pipe flow appears the same in rough as in smooth pipe flow. The relative turbulence intensity is constant, or at most decreases slowly with increase in flow Reynolds number. (Author).
| Author | : Jiyuan Tu |
| Publisher | : Butterworth-Heinemann |
| Total Pages | : 458 |
| Release | : 2012-11-07 |
| Genre | : Computers |
| ISBN | : 0080982433 |
An introduction to CFD fundamentals and using commercial CFD software to solve engineering problems, designed for the wide variety of engineering students new to CFD, and for practicing engineers learning CFD for the first time. Combining an appropriate level of mathematical background, worked examples, computer screen shots, and step by step processes, this book walks the reader through modeling and computing, as well as interpreting CFD results. The first book in the field aimed at CFD users rather than developers. New to this edition: A more comprehensive coverage of CFD techniques including discretisation via finite element and spectral element as well as finite difference and finite volume methods and multigrid method. Coverage of different approaches to CFD grid generation in order to closely match how CFD meshing is being used in industry. Additional coverage of high-pressure fluid dynamics and meshless approach to provide a broader overview of the application areas where CFD can be used. 20% new content .
| Author | : A. A. R. Townsend |
| Publisher | : Cambridge University Press |
| Total Pages | : 450 |
| Release | : 1976 |
| Genre | : Mathematics |
| ISBN | : 9780521298193 |
Develops a physical theory from the mass of experimental results, with revisions to reflect advances of recent years.
| Author | : Christian Bauer |
| Publisher | : Cuvillier Verlag |
| Total Pages | : 244 |
| Release | : 2021-02-01 |
| Genre | : Technology & Engineering |
| ISBN | : 3736963696 |
Die turbulente Rohrströmung ist nicht nur von großer Bedeutung für Anwendungen im Ingenieurbereich, sondern auch für die Grundlagenforschung von wandnaher Turbulenz. In der vorliegenden Arbeit wird die Interaktion sogenannter turbulenter Superstrukturen (engl.: very-large-scale motions, VLSMs) mit der kleinskaligen Wandturbulenz auf Basis der Methode der direkten numerischen Simulation untersucht. Dabei werden Schubspannungs-Reynoldszahlen bis Reτ = 2880 und Rohrlängen bis L = 42R berücksichtigt. Es wird das Konvergenz- und Skalierungsverhalten verschiedener statistischer Momente der Geschwindigkeitsverteilung untersucht und in Bezug auf VLSMs diskutiert. Die folgende Analyse der axialen Energietransportgleichung des gefilterten Geschwindigkeitsfeldes legt offen, dass VLSMs Energie von der mittleren Strömung zugeführt bekommen, ähnlich den kleinskaligen Strukturen durch den turbulenten Produktionsmechanismus. Die verschiedenen Terme der Energiebilanz werden sowohl anhand von mittleren Profilen, als auch instantanen Strömungsvisualisierungen und drei-dimensionalen Korrelationen diskutiert, wobei auch auf das Phänomen der inversen turbulenten Energiekaskade eingegangen wird. Die Forschungsarbeit gewährt dabei neue Einblicke in die Interaktion der VLSMs mit dem turbulenten Wandzyklus und trägt zum besseren Verständnis der turbulenten Rohrströmung bei. Turbulent pipe flow is not only of importance to engineering applications but also of fundamental interest to the study of wall-bounded turbulence. In the present work, the interaction of the so-called very-large-scale motions (VLSMs) with the near-wall, small-scale turbulence is explored by means of direct numerical simulation for friction Reynolds numbers up to Reτ = 2880 and pipe lengths up to L = 42R. Besides, the convergence and the scaling of different order moments of the velocity distribution are studied and also discussed with regard to VLSMs. The subsequent analysis of the streamwise energy budget equation of the filtered velocity field reveals that VLSMs obtain their energy from the mean velocity field via a production mechanism similar to the one known from the near-wall cycle. Moreover, the different energy budget terms are investigated by means of statistical averages, instantaneous flow field visualisations, and three-dimensional correlations, wherein the backscattering phenomenon is also dealt with. In brief, the research sheds new light on our understanding of the interaction between VLSMs and the near-wall cycle and leads to a better grasp of turbulent pipe flow in general.
| Author | : Russell J. Donnelly |
| Publisher | : Springer |
| Total Pages | : 498 |
| Release | : 1998-10-09 |
| Genre | : Science |
| ISBN | : |
Scientists have learned to use liquid and gaseous helium to overcome the limitations imposed by the usual wind and water tunnels for testing the performance of aircraft or the behavior of the atmosphere. This book covers fundamental studies of the turbulence problem, practical applications of turbulence, superfluid turbulence, cryogenic turbulence research, and new types of miniature flow instrumentation, all which are crucial for high Reynolds number research. This state-of-the-art presentation will interest physicists in fluid dynamics, engineers working with turbulent flows, and naval and aerospace engineers testing realistic parameter ranges.
