Download or read book Behaviour of Energetic Coherent Structures in Turbulent Pipe Flow at High Reynolds Numbers written by Zeinab Hallol and published by Cuvillier Verlag. This book was released on 2021-10-26 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Direct Numerical Simulation of Very Large Scale Motions in Turbulent Pipe Flow written by Christian Bauer and published by Cuvillier Verlag. This book was released on 2021-02-01 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Engineering Turbulence Modelling and Experiments 4 written by D. Laurence and published by Elsevier. This book was released on 1999-04-14 with total page 975 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Experiments in Pipe Flows at Transitional and Very High Reynolds Numbers written by Emir Öngüner and published by Cuvillier Verlag. This book was released on 2018-05-02 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Coherent Structures in Fully Developed Turbulent Pipe Flow written by Ioannis Constantinos Lekakis and published by . This book was released on 1988 with total page 504 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbulence Structure Associated with Intercomponent and Interscale Energy Transfer and Modification by Forcing written by James G.. Brasseur and published by . This book was released on 1993 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigation of High Reynolds Number Pipe Flow written by Franziska König and published by Cuvillier Verlag. This book was released on 2015-07-21 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Progress in Wall Turbulence 2 written by Michel Stanislas and published by Springer. This book was released on 2015-08-17 with total page 430 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book The Structure of Turbulent Shear Flow written by A. A. R. Townsend and published by Cambridge University Press. This book was released on 1976 with total page 450 pages. Available in PDF, EPUB and Kindle. Book excerpt: Develops a physical theory from the mass of experimental results, with revisions to reflect advances of recent years.

Download or read book Plasma Engineering written by Michael Keidar and published by Academic Press. This book was released on 2018-08-06 with total page 587 pages. Available in PDF, EPUB and Kindle. Book excerpt: Plasma Engineering, Second Edition, applies the unique properties of plasmas (ionized gases) to improve processes and performance over many fields, such as materials processing, spacecraft propulsion and nanofabrication. The book considers this rapidly expanding discipline from a unified standpoint, addressing fundamentals of physics and modeling, as well as new and real-word applications in aerospace, nanotechnology and bioengineering. This updated edition covers the fundamentals of plasma physics at a level suitable for students using application examples and contains the widest variety of applications of any text on the market, spanning the areas of aerospace engineering, nanotechnology and nanobioengineering. This is highly useful for courses on plasma engineering or plasma physics in departments of Aerospace Engineering, Electrical Engineering and Physics. It is also useful as an introduction to plasma engineering and its applications for early career researchers and practicing engineers. - Features new material relevant to application, including emerging areas of plasma nanotechnology and medicine - Contains a new chapter on plasma-based control, as well as a description of RF and microwave-based plasma applications, plasma lighting, reforming and other most recent application areas - Provides a technical treatment of the fundamental and engineering principles used in plasma applications

Download or read book Coherent Flow Structures at Earth s Surface written by Jeremy G. Venditti and published by John Wiley & Sons. This book was released on 2013-08-28 with total page 586 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1992 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Turbulence in Open Channel Flows written by Hiroji Nakagawa and published by Routledge. This book was released on 2017-10-02 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt: A review of open channel turbulence, focusing especially on certain features stemming from the presence of the free surface and the bed of a river. Part one presents the statistical theory of turbulence; Part two addresses the coherent structures in open-channel flows and boundary layers.

Download or read book Experiments in High Reynolds Number Turbulent Pipe Flow written by M. V. Zagarola and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advanced Approaches in Turbulence written by Paul Durbin and published by Elsevier. This book was released on 2021-07-24 with total page 554 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advanced Approaches in Turbulence: Theory, Modeling, Simulation and Data Analysis for Turbulent Flows focuses on the updated theory, simulation and data analysis of turbulence dealing mainly with turbulence modeling instead of the physics of turbulence. Beginning with the basics of turbulence, the book discusses closure modeling, direct simulation, large eddy simulation and hybrid simulation. The book also covers the entire spectrum of turbulence models for both single-phase and multi-phase flows, as well as turbulence in compressible flow. Turbulence modeling is very extensive and continuously updated with new achievements and improvements of the models. Modern advances in computer speed offer the potential for elaborate numerical analysis of turbulent fluid flow while advances in instrumentation are creating large amounts of data. This book covers these topics in great detail. - Covers the fundamentals of turbulence updated with recent developments - Focuses on hybrid methods such as DES and wall-modeled LES - Gives an updated treatment of numerical simulation and data analysis

Download or read book High Reynolds Number Turbulent Pipe Flow written by Beverley J. McKeon and published by . This book was released on 2003 with total page 726 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dynamical Systems and Bifurcation Theory written by M. I. Camacho and published by . This book was released on 1987 with total page 446 pages. Available in PDF, EPUB and Kindle. Book excerpt: