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Über dieses Buch

This book presents experimental techniques in the field of aerodynamics, a discipline that is essential in numerous areas, such as the design of aerial and ground vehicles and engines, the production of energy, and understanding the wind resistance of buildings. Aerodynamics is not only concerned with improving the performance and comfort of vehicles, but also with reducing their environmental impact. The book provides updated information on the experimental and technical methods used by aerodynamicists, engineers and researchers. It describes the various types of wind tunnels – from subsonic to hypersonic – as well as the problems posed by their design and operation. The book also focuses on metrology, which has allowed us to gain a detailed understanding of the local properties of flows, and examines current developments toward creating a methodology combining experiments and numerical simulations: the computer-assisted wind tunnel. Lastly, it offers an overview of experimental aerodynamics based on a prospective vision of the discipline, and discusses potential futures challenges.

The book can be used as a textbook for graduate courses in aerodynamics, typically offered to students of aerospace and mechanical engineering programs, and as a learning tool for professionals and engineers in the fields of aerodynamics, aeronautics and astronautics automobile.

Inhaltsverzeichnis

Frontmatter

Chapter 1. The Experimental Approach in Aerodynamic Design

Abstract
Aerodynamics is the study of the flow of air around bodies, generally an aerial or ground vehicle, but also structures, turbomachine blades and rotors, wind turbines, or in more diverse cases such as bikes and other sports equipments.
Bruno Chanetz, Jean Délery, Patrick Gilliéron, Patrick Gnemmi, Erwin R. Gowree, Philippe Perrier

Chapter 2. Wind Tunnels and Other Aerodynamic Test Facilities

Abstract
The wind tunnel is a means of studying and understanding the behaviour of an aerial or ground vehicle by performing an experiment, usually on a scaled model.
Bruno Chanetz, Jean Délery, Patrick Gilliéron, Patrick Gnemmi, Erwin R. Gowree, Philippe Perrier

Chapter 3. Subsonic Wind Tunnels

Abstract
Built by Gustave Eiffel, and still in use, the low speed wind tunnel at the Scientific and Technical Centre for Building (CSTB) located in Auteuil was inaugurated on 19 March 1912 (see Fig. 2.​1).
Bruno Chanetz, Jean Délery, Patrick Gilliéron, Patrick Gnemmi, Erwin R. Gowree, Philippe Perrier

Chapter 4. Transonic Wind Tunnels

Abstract
As the air flow around an aircraft is not uniform, locally supersonic zones may exist even under subsonic upstream flow condition, this defines the transonic regime, a condition where both subsonic and supersonic regions coexist.
Bruno Chanetz, Jean Délery, Patrick Gilliéron, Patrick Gnemmi, Erwin R. Gowree, Philippe Perrier

Chapter 5. Supersonic Wind Tunnels

Abstract
To begin with, the generation of a supersonic flow requires a convergent duct and an upstream/downstream pressure ratio sufficient to achieve sonic velocity at the duct minimum section or throat.
Bruno Chanetz, Jean Délery, Patrick Gilliéron, Patrick Gnemmi, Erwin R. Gowree, Philippe Perrier

Chapter 6. Hypersonic Wind Tunnels

Abstract
Hypersonic wind tunnels are intended for studying the aerodynamics of hypersonic aircraft, space launchers, missiles, projectiles and the atmospheric re-entry of space vehicles.
Bruno Chanetz, Jean Délery, Patrick Gilliéron, Patrick Gnemmi, Erwin R. Gowree, Philippe Perrier

Chapter 7. Flow Visualisation Techniques

Abstract
In aerodynamics and more generally fluid mechanics one has the invaluable advantage of being interested in the physical phenomena that can be visualised directly, unlike other disciplines where only the consequences of the phenomena can be observed.
Bruno Chanetz, Jean Délery, Patrick Gilliéron, Patrick Gnemmi, Erwin R. Gowree, Philippe Perrier

Chapter 8. Measurement of Aerodynamic Forces and Moments

Abstract
The presence of the flow around a vehicle exerts aerodynamic forces and moments, which act at the centre of pressure.
Bruno Chanetz, Jean Délery, Patrick Gilliéron, Patrick Gnemmi, Erwin R. Gowree, Philippe Perrier

Chapter 9. Characterisation of Flow Properties at the Surface

Abstract
The main forces acting locally on a surface experiencing a fluid flow are due to the pressure and the wall friction, the latter being responsible for heat transfer between the surface and the fluid.
Bruno Chanetz, Jean Délery, Patrick Gilliéron, Patrick Gnemmi, Erwin R. Gowree, Philippe Perrier

Chapter 10. Intrusive Measurement Techniques

Abstract
Even nowadays the flow is still diagnosed by solid probes such as Pitot probes, thermocouples and hot wires in particular, it has been crucial in not only capturing the mean flow, but also in providing further insight into coherent structures. Despite more sophisticated measurement techniques, in many cases their use is justified by their accuracy, reliability, cost and simplicity. The main drawback are their intrusive effects, leading to scepticism during the measurement of shear layer developed by a separated flow and are more delicate in transonic flow. Besides, to avoid vibration of the probe the struts and mounts have the tendency to be voluminous and this introduces solid blockage which has an impact on the desired pressure distribution. Also, during spatial characterisation of the flow, complex and expensive traverse system is usually required and the displaced position of the strut could again impair with the local and overall pressure gradient. During the measurement in low pressure turbines and hypersonic flows, the probes need to be able to withstand very high temperature without disintegrating or deforming due to thermal expansions. An operational limit is usually set at approximately 1200 K and above this temperature more exotic material or sometimes cooling systems are required, which increases cost and complexity of the technique. In confined experimental facilities where reduced scale, miniature models are tested, deformation and vibration of the probes introduces large uncertainty in terms of positioning of the probe and hence compromising significantly the end result.
Bruno Chanetz, Jean Délery, Patrick Gilliéron, Patrick Gnemmi, Erwin R. Gowree, Philippe Perrier

Chapter 11. Non-intrusive Measurement Techniques

Abstract
Non-intrusive measurement techniques are based on optical techniques and have tremendous advantages, but as all measurement techniques they have their limitations and drawbacks. Aside the arduous technical issues associated with data processing and analysis, their main physical limitation is simply based on visual access of the experimental domain of interest and also the ability to guide the light/laser source for sufficient illumination. This depends a lot on the experimental facility and sometimes the working section has to be redesigned and equipped with sufficiently large windows with high optical quality glass or Perspex which is a strict requirement for classical interferometry techniques.
Bruno Chanetz, Jean Délery, Patrick Gilliéron, Patrick Gnemmi, Erwin R. Gowree, Philippe Perrier

Chapter 12. Laser Spectroscopy and Electron Beam Excitation

Abstract
The advent of laser sources in the 1960s gave considerable impetus to the development of non-intrusive methods for the in situ determination of gas properties, including the velocity. These methods are based on physical processes related to the interaction between light and matter. The analysis of the resulting phenomena makes it possible to deduce the characteristics of the atoms and/or molecules composing the gas being tested and to measure properties such as its nature, concentration, energy levels, etc. Although these methods are not commonly used in aerodynamic applications because of their sophistication and limitations, they are powerful tools for studying complex flows. In particular, they give access to species concentration, local pressure, temperature and are of great interest for the study of very high temperature flows or flows containing chemically active combustion products.
Bruno Chanetz, Jean Délery, Patrick Gilliéron, Patrick Gnemmi, Erwin R. Gowree, Philippe Perrier

Chapter 13. Computer-Aided Wind Tunnel Test and Analysis

Abstract
Currently in aeronautics the aims and objectives of wind tunnels experiment are diverse. It could be purely for optimising the aerodynamic design at the high speeds (transonic for the transport aircraft) by conceiving efficient wing sections, coupling the structure and aerodynamics (optimised volume, lighter structure, aeroelastic behaviour), developing innovative deployable surfaces to achieve high lift at low speed, controlling the plane’s behaviour (performance, manoeuvrability and flight envelope) up to maximum lift coefficient and beyond stall. In the field of terrestrial vehicles, the objectives are to decrease the drag in order to reduce the fuel consumption, to guarantee the stability of the vehicle (response to cross wind) and to increase interior comfort by reducing aerodynamic noise.
Bruno Chanetz, Jean Délery, Patrick Gilliéron, Patrick Gnemmi, Erwin R. Gowree, Philippe Perrier

Chapter 14. Prospects and Challenges for Aerodynamics

Abstract
The wind tunnel is a major constituent of a specialised infrastructure for research in aeronautics and aerospace. Its contribution and importance over-match the experimental facilities required in many other sectors for research and development. In the absence of a complete tool set to design next generation vehicles, the design cycle can only be matured through joint CFD simulation and wind tunnel testing, where the latter is able to represent most of the physical phenomena that could be encountered during operation. This is a major source of disparity between CFD and wind tunnel results as CFD is still unable to reproduce or model the exact physics usually due to limitations in the choice of boundary conditions and realistic computational time and cost.
Bruno Chanetz, Jean Délery, Patrick Gilliéron, Patrick Gnemmi, Erwin R. Gowree, Philippe Perrier

Backmatter

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