Behaviour Of Energetic Coherent Structures In Turbulent Pipe Flow At High Reynolds Numbers
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| 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 | : 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 | : Emir Öngüner |
| Publisher | : Cuvillier Verlag |
| Total Pages | : 162 |
| Release | : 2018-05-02 |
| Genre | : Technology & Engineering |
| ISBN | : 3736987838 |
The present work aims at investigating the turbulence in pipe flow. Experiments have been performed in two unique pipe facilities: CoLaPipe (CottbusLarge-Pipe) and CICLoPE (Center for International Cooperation in Long Pipe Experiments). The first part of the thesis is focusing on the development of flow considering pressure fluctuations measured along the axial direction to find the location where the flow becomes fully developed turbulent. Results show that application of ring disturbance to the incoming flow initiates turbulence much earlier upstream. The second aim of the thesis is determining the streamwise lengths of large-scale structures in fully developed turbulent state with respect to their wavenumber dependency and spatial correlation using hot-wire anemometry and Particle Image Velocimetry. Meandering structures usually referred as VLSM (very large-scale motions), have been identified with claimed extension up to 20R, where R is the pipe radius. The location of the outer spectral peaks (OSP) which represent the largest energy content per wavenumber outside the viscous wall region is moving towards to the wall as the Reynolds number increases.
| Author | : Ioannis Constantinos Lekakis |
| Publisher | : |
| Total Pages | : 504 |
| Release | : 1988 |
| Genre | : Turbulence |
| ISBN | : |
| Author | : D. Laurence |
| Publisher | : Elsevier |
| Total Pages | : 975 |
| Release | : 1999-04-14 |
| Genre | : Science |
| ISBN | : 0080530982 |
These proceedings contain the papers presented at the 4th International Symposium on Engineering Turbulence Modelling and Measurements held at Ajaccio, Corsica, France from 24-26 May 1999. It follows three previous conferences on the topic of engineering turbulence modelling and measurements. The purpose of this series of symposia is to provide a forum for presenting and discussing new developments in the area of turbulence modelling and measurements, with particular emphasis on engineering-related problems. Turbulence is still one of the key issues in tackling engineering flow problems. As powerful computers and accurate numerical methods are now available for solving the flow equations, and since engineering applications nearly always involve turbulence effects, the reliability of CFD analysis depends more and more on the performance of the turbulence models. Successful simulation of turbulence requires the understanding of the complex physical phenomena involved and suitable models for describing the turbulent momentum, heat and mass transfer. For the understanding of turbulence phenomena, experiments are indispensable, but they are equally important for providing data for the development and testing of turbulence models and hence for CFD software validation.
| Author | : James G.. Brasseur |
| Publisher | : |
| Total Pages | : 24 |
| Release | : 1993 |
| Genre | : Reynolds number |
| ISBN | : |
| 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 | : Michel Stanislas |
| Publisher | : Springer |
| Total Pages | : 430 |
| Release | : 2015-08-17 |
| Genre | : Technology & Engineering |
| ISBN | : 3319203886 |
This is the proceedings of the ERCOFTAC Workshop on Progress in Wall Turbulence: Understanding and Modelling, that was held in Lille, France from June 18 to 20, 2014. The workshop brought together world specialists of near wall turbulence and stimulated exchanges between them around up-to-date theories, experiments, simulations and numerical models. This book contains a coherent collection of recent results on near wall turbulence including theory, new experiments, DNS and modeling with RANS, LES. The fact that both physical understanding and modeling by different approaches are addressed by the best specialists in a single workshop is original.
| 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 | : Jeremy G. Venditti |
| Publisher | : John Wiley & Sons |
| Total Pages | : 586 |
| Release | : 2013-08-28 |
| Genre | : Science |
| ISBN | : 1118527194 |
An expert review of recent progress in the study of turbulent flows with a focus on recently identified organized structures. This book reviews the recent progress in the study of the turbulent flows that sculpt the Earth’s surface, focusing in particular on the organized structures that have been identified in recent years within turbulent flows. These coherent flow structures can include eddies or vortices at the scale of individual grains, through structures that scale with the flow depth in rivers or estuaries, to the large-scale structure of flows at the morphological or landform scale. These flow structures are of wide interest to the scientific community because they play an important role in fluid dynamics and influence the transport, erosion and deposition of sediment and pollutants in a wide variety of fluid flow environments. Scientific knowledge of these structures has improved greatly over the past 20 years as computational fluid dynamics has come to play an increasing important part in building our understanding of coherent flow structures across a broad range of scales. Chapters comprise a series of major, invited papers and a selection of the most novel, innovative papers presented at the second Coherent Flow Structures Conference held August 3-5, 2011 at Simon Fraser University in Burnaby, British Columbia. Chapters focus on six major themes: Dynamics of coherent flow structures (CFS) in geophysical flows Interaction of turbulent flows, vegetation and ecological habitats Coherent structure of atmospheric flows Numerical modeling of coherent flow structures Turbulence in open channel flows Coherent flow structures, sediment transport and morphological feedbacks.
