Handbook of Shock Waves
Preface to the Handbook
Shock waves have fascinated mankind from the dawn of history.
Before the discovery of explosive materials the commonly encountered
shock waves were thunders. Until the 17^{th} century such
violent phenomena were enshrouded in mystery and they were related
to evil powers. As mentioned in section 1.4.1 Earnshow (1851) was
probably the first who related the thunder propagation to supersonic
velocity. Now we know that shock waves result from a very sudden
release of chemical, electrical, nuclear, or mechanical energy in
a limited space. In nature the most frequently encountered shock
wave is the thunder that follows the lightning. Shock waves are
also associated with earthquakes and volcanic eruptions. A typical
manmade shock wave results from the detonation of explosive materials.
Also, complex shock wave structures appear in all supersonic flights.
These all can range from weak shock waves associated with the use
of any firearm up to shock waves resulting from nuclear explosions
reaching enormous magnitudes. In descriptive terms, a shock wave
is a very sharp, thin front through which there exists a sudden
change in all flow properties, such as pressure, temperature, density,
velocity and entropy. At standard atmospheric conditions the width
of a shock wave front is about 2.5 Angstrom.
Shock waves appear in many forms and in various
media. In the Handbook of Shock Waves we have tried to cover
as many as possible of these forms. Firstly, in Chapter 1, a brief
historical description indicating milestones of shock wave research
and activities starting in the sixteen century and continuing up
to the end of the Second World War is given. It was decided to end
the historical survey at 1945 since many of the postwar investigations
are presented in the various chapters of the Handbook.
General propagation laws governing shock wave transmission
through matter is are outlined in Chapter 2, in which the basic
equations governing shock wave propagation are presented. These
equations are used in subsequent chapters.
In Chapter 3.1 a detailed description of shock
wave propagation in gases is given; shock wave propagation in liquids
follows in Chapter 3.2 and shock wave propagation in solids in Chapter
3.3. The rest of Chapter 3 is dedicated to special aspects of shock
waves in gases. In Chapter 3.4 the unique case of rarefaction shocks
is discussed; this is followed, in Chapter 3.5, by a discussion
on shock wave stability. Although most of the Handbook deals
with shock waves on earth and in the earth atmosphere, shock waves
are not limited to our planet. One of the theories explaining the
creation of the universe is via the 'bigbang', which is the ultimate
shock wave. Shock waves are daily events in the sun's corona and
a frequent occurrence in the solar wind in space. Chapter 3.6 is
devoted to shock waves in space.
For experimental studies of shock waves one needs
facilities that can generate flows in which shock waves appear in
a laboratory environment. Furthermore, special diagnostics systems
are required in order to detect, observe and provide records enabling
the analysis of a laboratorygenerated shock. In Chapter 4 various
facilities suitable for the generation of shock waves are presented.
The classical shock tube facility and the flow field it produces
are outlined in Chapter 4.1. The extension of the shock tube concept
to shock tunnels and piston driven shock and expansion tunnels is
described in Chapters 4.2 and 4.3, respectively. The various shock
tube facilities described in Chapters 4.1 to 4.3 are primarily designed
to produce step like shock waves, i.e., shock waves associated with
a sudden jump between two different, uniform states.
However, shocks generated in the atmosphere, i.e.,
blast waves, are usually different from those defined above. In
such waves fast pressure decay follows the sudden jump in the pressure
across the shock front. Chapter 4.4 describes blast tubes, which
are facilities suitable for producing blast waves. A common feature
to all facilities described in chapters 4.1 to 4.4 is the fact that
they all produce very short duration flows, significantly less than
a second. When longer flow durations are needed, for example if
steady flow is studied, one resorts to supersonic and hypersonic
wind tunnels. The flow duration in such facilities is measured in
minutes. The construction and operation of supersonic and hypersonic
wind tunnels is described in Chapter 4.5. Experimental investigation
of shock wave phenomena requires, in addition to the facility for
producing shock waves, appropriate measuring techniques. Such devices
must have extremely short response times, should not disturb the
investigated flow field and should produce unambiguous results.
A survey of diagnostic techniques suitable for flow visualization
is given in Chapter 5.1. A complementary diagnostic used for studying
high temperature flows generated behind strong shock waves, is spectroscopy.
This technique is presented in Chapter 5.2.
Until the late 1960's most of the shock wave investigations
were experimental. This was an unavoidable consequence of the fact
that the equations of motion governing shock wave generated flows
are nonlinear. Only for special flow conditions do such equations
have analytical solutions. Otherwise, a numerical solution is the
only available option. This option became feasible only after the
rapid development in computer software and hardware that started
in the 1970's. Today, numerical analysis is replacing experimental
investigation as a primary tool in studying shock wave phenomena.
Many different codes have been developed especially for studying
shock wave phenomena. The major ones are described in Chapter 6
where numerical methods suitable for investigating shock wave phenomena
are discussed.
The rest of the Handbook deals with some
specific types and aspects of shock wave phenomena. In Chapter 7
the simplest shock wave generated flow and wave interactions, the
onedimensional flow case, is discussed. The natural second step,
described in Chapter 8, is the twodimensional wave interaction.
In Chapter 8.1 reflections of oblique shock waves from rigid surfaces
are discussed. Shock wave refraction is presented in Chapter 8.2,
followed, in Chapter 8.3, by a description of shock waves interactions
with boundary layers. This complex process is of major importance
because it appears in real supersonic flows over bodies. A special
case of twodimensional flow is that resulting from shock wave reflection
from axisymmetric bodies; such cases are the topic of Chapter 9.
Propagation of shock waves in straight tunnels
was described while discussing shock tube facilities (Chapter 4.1)
and onedimensional interactions (Chapter 7). In practice one encounters
tunnels in which there are bends, curvatures, splittings and other
obstacles. Obviously, such additions spoil the onedimensional nature
of the flow and thereby increase the complexity of the prevailing
flow field. Chapter 10 treats, theoretically, experimentally and
numerically shock wave propagation in channels of different geometry.
A special case of onedimensional shock wave flow
is the case in which the flow has a spherical symmetry. Spherical
shock waves result from detonation of spherical explosives. These
shocks decay as they expand until they reduce to sound waves. Their
fast decay is a direct result of the fact that a given amount of
energy is spread out over an everincreasing volume of fluid. The
opposite is true for spherical shock waves that propagate towards
the center namely, imploding shocks. In such cases the shock strength
increases as it approaches the center. The physical background of
imploding shock waves is outline in Chapter 11 where shock wave
focusing is discussed. Shock wave focusing is the cornerstone of
lithotripsy, a technique employed for shattering kidney stones.
Recently it was extended for usage in ophthalmology, gene therapy,
thrombus ablation and food preservation. Details regarding these
recent applications are given in Chapter 12 where the application
of shock waves in medicine is discussed. A survey of expanding spherical
shock waves (blast waves) is given in Chapter 13.1. The last chapter
discussing spherical shocks, Chapter 13.2, provides a general attenuation
law for spherical expanding shock waves.
An important topic that has drawn attention in
recent years is shockinduced instabilities of interfaces separating
different gases or phases. This is the topic of Chapter 14. Chapter
15 deals with various aspects of shock wave propagation in multiphase
media. In Chapter 15.1 shock wave propagation in porous media is
presented. The considered media are composed of deformable or rigid
skeletons whose voids are filled with gas. A special case of porous
media is a granular medium. In such a case the skeleton is composed
of small solid particles packed on together. Propagation of shock
waves in granular media is the topic of Chapter 15.2. Cases of twophase
flow are discussed in Chapters 15.3 and 15.4. The former deals with
shock wave in inert and reactive bubbly liquids and the latter with
shock wave propagation in liquidgas suspensions.
The last part of the Handbook, Volume 3
whose editing was done by Professor Assa Lifshitz of the Hebrew
University in Jerusalem, is dedicated to chemical reactions taking
place in the hot postshock flow. These topics are considered in
Chapter 16. A special case of chemical reactions induced by strong
shock waves propagating in a combustible gas mixture is the case
of combustion, detonation and deflagration. This topic is covered
in Chapter 17.
The present Handbook is the result of a
cooperative effort of 47 scientists from 15 countries, each knowledgeable
in his own field. We hope it will serve as a useful source of information
for scientists, engineers and students active in shock wave research.
Although we have tried to cover as many aspects of shock wave phenomena
as we could, we are fully aware that this is a target one may approach
but not necessarily reach. It is hoped that in future editions additional
topics will be added.
Many scientists, engineers and students around
the world are engaged in shock wave studies. Each has his reason
for being attracted to investigating these phenomena. For two of
us (Gabi BenDor and Ozer Igra) it was the late Professor Irvine
I. Glass who opened the door to the world of shock waves and was
our guide through this fascinating subject while we took our early
steps in the field of shock wave phenomena. We are grateful to him
for introducing us to the path along which we continue to walk with
ever increasing interest.
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