while exiting Earth's atmosphere at high altitude. The realisation of hypersonic
testing requires the generation of flows not only at high Mach number but also with
high specific energy. Because of the very high speeds encountered during the
atmospheric re-entry, high levels of thermodynamic effects are present.
Much of the book is devoted to the means of diagnosis and characterisation of
flows, including very valuable visualisation techniques presented in Chap. 7, and
the measurement of the aerodynamic forces and moments exerted on the vehicle by
the fluid in motion is addressed in Chap. 8. The determination of the surface
properties such as pressure, skin friction and heat transfer is of fundamental
importance in most applications; the techniques are visited in Chap. 9. In addition
to the traditional measurement by static pressure at the wall using pressure tappings,
the use of more recently developed Pressure Sensitive Paints (PSP) allows for the
global wall pressure distribution over a larger and sometimes whole part of the
model to be captured without the need for discrete intrusive, expensive and cumbersome pressure sensors and data acquisition system. Similar progress is made in
the measurement of heat transfer while increasingly competing with optical
methods like infrared thermography or the use of temperature-sensitive paints
(TSP).
The local properties of the flow (pressure and velocity in particular) are still
determined by standard means such as pressure probes or thermocouples for the
stagnation pressure and temperature. Hot wire is still widely used for time-averaged
velocity measurements, and due to its very short response time, it is still the most
reliable technique for measurement of velocity fluctuations and turbulence scales,
and this will be covered in Chap. 10.
Chapter 11 presents the so-called non-intrusive techniques for in situ measurement of flow properties, mainly velocity. This is an essential part of the book. These
means of characterisation of flows have undergone a real breakthrough with the
advent of more affordable lasers and remarkable advances in the field of optronics
and data processing. At first, laser Doppler velocimetry (LDV) and then particle
image velocimetry (PIV) have been essential tools to capture and resolve very
complex flow phenomena and have now become commonplace in almost all
aerodynamics laboratories.
The development of techniques based on the excitation of molecules or atoms
of the gas by laser or electron beam has allowed the development of methods
without the need to seed the flow by particles, unlike in LDV and PIV.
Spectroscopic techniques give access to the gas properties such as pressure, temperature, density and also to its velocity and composition in the case of reactive
flows. They are widely used in the study of hypersonic flows and will be discussed
in Chap. 12.
Preface
ix
testing requires the generation of flows not only at high Mach number but also with
high specific energy. Because of the very high speeds encountered during the
atmospheric re-entry, high levels of thermodynamic effects are present.
Much of the book is devoted to the means of diagnosis and characterisation of
flows, including very valuable visualisation techniques presented in Chap. 7, and
the measurement of the aerodynamic forces and moments exerted on the vehicle by
the fluid in motion is addressed in Chap. 8. The determination of the surface
properties such as pressure, skin friction and heat transfer is of fundamental
importance in most applications; the techniques are visited in Chap. 9. In addition
to the traditional measurement by static pressure at the wall using pressure tappings,
the use of more recently developed Pressure Sensitive Paints (PSP) allows for the
global wall pressure distribution over a larger and sometimes whole part of the
model to be captured without the need for discrete intrusive, expensive and cumbersome pressure sensors and data acquisition system. Similar progress is made in
the measurement of heat transfer while increasingly competing with optical
methods like infrared thermography or the use of temperature-sensitive paints
(TSP).
The local properties of the flow (pressure and velocity in particular) are still
determined by standard means such as pressure probes or thermocouples for the
stagnation pressure and temperature. Hot wire is still widely used for time-averaged
velocity measurements, and due to its very short response time, it is still the most
reliable technique for measurement of velocity fluctuations and turbulence scales,
and this will be covered in Chap. 10.
Chapter 11 presents the so-called non-intrusive techniques for in situ measurement of flow properties, mainly velocity. This is an essential part of the book. These
means of characterisation of flows have undergone a real breakthrough with the
advent of more affordable lasers and remarkable advances in the field of optronics
and data processing. At first, laser Doppler velocimetry (LDV) and then particle
image velocimetry (PIV) have been essential tools to capture and resolve very
complex flow phenomena and have now become commonplace in almost all
aerodynamics laboratories.
The development of techniques based on the excitation of molecules or atoms
of the gas by laser or electron beam has allowed the development of methods
without the need to seed the flow by particles, unlike in LDV and PIV.
Spectroscopic techniques give access to the gas properties such as pressure, temperature, density and also to its velocity and composition in the case of reactive
flows. They are widely used in the study of hypersonic flows and will be discussed
in Chap. 12.
Preface
ix