The Turbulence Structure Of Trailing Vortice Wakes

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The present investigation is a two-part study of the mean flow and turbulence structure of isolated vortices and counter-rotating vortex pairs. In the first part, the turbulence structure of an isolated vortex was studied using three-component velocity measurements. Vortices were generated using two symmetrical airfoils. Measurements were made in cross-sectional grids and profiles over a range of Reynolds numbers and downstream distances. Contours of axial normal stress were high-pass filtered to remove the contributions of wandering to the velocity fluctuations. This process reveals a vortex core which is laminar and is surrounded by a region of high turbulence. Core velocity profiles reveal that maximum tangential velocity increases with Reynolds number and decreases with distance downstream. Core radius increases with distance downstream and decreases with Reynolds number. In the second part, flow visualizations of the wake behind a delta wing model were made for a range of Reynolds numbers and lift coefficients. These visualizations reveal the near-instantaneous turbulence structure of the wing wake which is dominated by a vortex pair and a connecting 'braid' wake. The braid spacing decreases with increasing Reynolds number and is independent of lift coefficient. The extent of the braid downstream of the wing increases with lift coefficient and decreases with increasing Reynolds number. The large turbulence scales in the wing wake were found to increase in discrete jumps indicating some sort of reorganization of turbulence such as pairing. This reorganization of turbulence was found to occur more quickly as Reynolds number is increased.

Advances In Turbulence Vi

Autore: S. Gavrilakis
Editore: Springer Science & Business Media
ISBN: 9400902972
Grandezza: 32,86 MB
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Advances in Turbulence VI presents an update on the state of turbulence research with some bias towards research in Europe, since it represents an almost complete collection of the paper presentations at the Sixth European Turbulence Conference, sponsored by EUROMECH, ERCOFTAC and COST, and held at the Swiss Federal Institute of Technology in Lausanne, July 2-5, 1996. The problem of transition, together with the structural description of turbulence, and the scaling laws of fully developed turbulence have continued to receive most attention by the research community and much progress has been made since the last European Turbulence Conference in 1994. The volume is thus geared towards specialists in the area of flow turbulence who could not attend the conference, as well as anybody who wishes quickly to assess the most active current research areas and the groups associated with them.

Turbulence Structure And Vortex Dynamics

Autore: J. C. Vassilicos
Editore: Cambridge University Press
ISBN: 9780521781312
Grandezza: 17,29 MB
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Edited volume on turbulence, first published in 2000.

Aircraft Wake Turbulence And Its Detection

Autore: John Olsen
Editore: Springer Science & Business Media
ISBN: 1468483463
Grandezza: 75,92 MB
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The combination of increasing airport congestion and the ad vent of large transports has caused increased interest in aircraft wake turbulence. A quantitative understanding of the interaction between an aircraft and the vortex wake of a preceding aircraft is necessary for planning future high density air traffic patterns and control systems. The nature of the interaction depends on both the characteristics of the following aircraft and the characteristics of the wake. Some of the questions to be answered are: What deter mines the full characteristics of the vortex wake? What properties of the following aircraft are important? What is the role of pilot response? How are the wake characteristics related to the genera ting aircraft parameters? How does the wake disintegrate and where? Many of these questions were addressed at this first Aircraft Wake Turbulence Symposium sponsored by the Air Force Office of Sci entific Research and The Boeing Company. Workers engaged in aero dynamic research, airport operations, and instrument development came from several count ries to present their results and exchange information. The new results from the meeting provide a current picture of the state of the knowledge on vortex wakes and their interactions with other aircraft. Phenomena previously regarded as mere curiosities have emerged as important tools for understanding or controlling vortex wakes. The new types of instability occurring within the wake may one day be used for promoting early dis integration of the hazardous twin vortex structure.

Numerical And Physical Aspects Of Aerodynamic Flows Iv

Autore: Tuncer Cebeci
Editore: Springer Science & Business Media
ISBN: 3662026430
Grandezza: 62,22 MB
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This volume contains a selection of the papers presented at the Fourth Symposium on Numerical and Physical Aspects of Aerodynamic Flows, which was held at the California State University, Long Beach, from 16-19 January 1989. It includes the Stewartson Memorial Lecture of Professor J. H. Whitelaw, and is divided into three parts. The first is a collection of papers that describe the status of current technology in two- and three-dimensional steady flows, the second deals with two- and three-dimensional unsteady flows, and the papers in the third address stability and transition. Each of the three parts begins with an overview of current research, as described in the following chapters. The individual papers are edited versions of the selected papers originally submitted to the symposium. Four years have passed since the Third Symposium, and certain trends be come clear if one compares the papers contained in this volume with those of previous volumes. There are more three- than two-dimensional problems consid ered in Part 1 and the latter address more difficult problems than in the past, for example, the extension to higher angles of attack, to transonic flow, to leading edge ice accretion, and to thick hydrofoils. The large number of papers in the first part reflects the emphasis of current research and development and the needs of industry.

Naca 0015 Wing Pressure And Trailing Vortex Measurements

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Editore: DIANE Publishing
ISBN: 142891546X
Grandezza: 51,43 MB
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Vortex Wakes Of Aircrafts

Autore: A.S. Ginevsky
Editore: Springer Science & Business Media
ISBN: 3642017606
Grandezza: 64,83 MB
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Investigation of vortex wakes behind various aircraft, especially behind wide bodied and heavy cargo ones, is of both scientific and practical in terest. The vortex wakes shed from the wing’s trailing edge are long lived and attenuate only atdistances of10–12kmbehindthe wake generating aircraft. The encounter of other aircraft with the vortex wake of a heavy aircraft is open to catastrophic hazards. For example, air refueling is adangerous operationpartly due to thepossibility of the receiver aircraft’s encountering the trailing wake of the tanker aircraft. It is very important to know the behavior of vortex wakes of aircraft during theirtakeoff andlanding operations whenthe wakes canpropagate over the airport’s ground surface and be a serious hazard to other depart ing or arriving aircraft. This knowledge can help in enhancing safety of aircraft’s movements in the terminal areas of congested airports where the threat of vortex encounters limits passenger throughput. Theoreticalinvestigations of aircraft vortex wakes arebeingintensively performedinthe major aviationnations.Usedforthispurpose are various methods for mathematical modeling of turbulent flows: direct numerical simulation based on the Navier–Stokes equations, large eddy simulation using the Navier–Stokes equations in combination with subrigid scale modeling, simulation based on the Reynolds equations closed with a differential turbulence model. These approaches are widely used in works of Russian and other countries’ scientists. It should be emphasized that the experiments in wind tunnels and studies of natural vortex wakes behind heavy and light aircraft in flight experiments are equally important.

Turbulent Shear Flows 4

Autore: L.J.S. Bradbury
Editore: Springer Science & Business Media
ISBN: 3642699960
Grandezza: 47,26 MB
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The Fourth International Symposium on Turbulent Shear Flows took place at Karlsruhe University in Germany. The papers presented at this Symposium encompassed a similar range to that of the previous meetings, with greater emphasis placed on experimental work, and continued a trend towards the examination of complex flows. Once again, three dimensional, recirculating and reacting flows featured strongly in the programme and were complemented by consideration of two-phase flows and discussions of both numerical and experimental techniques. The Symposium brought together some 300 participants from all over the world, and it was evident that there is a need for Turbulent Shear Flows Symposia, in order to obtain and communicate new information useful to researchers in the field of turbulent flows and of interest to engineers who design flow equipment. This volume contains 27 papers selected from more than 100 presentations at the Symposium which have been reviewed and edited before publication. Together they provide an indication of the status of current knowledge on the subjects represented at the Sympo sium. They are grouped into four sections, namely: • Fundamentals • Free Flows • Boundary Layers • Reacting Flows As in previous volumes in this series, each section begins with an introductory article con sidering the papers which follow in the broader context of available literature and current research.