Introduction to Interactive Boundary Layer Theory by Ian Sobey, Oxford
University Press, 拢45, ISBN 0198506759
Turbulent Flows by Stephen Pope, Cambridge University Press, 拢29.95,
ISBN 0521598869
THE actions of fluids intrigue artists, engineers, biologists and physicists
alike. Leonardo da Vinci鈥檚 drawings of turbulent eddies testify as much.
Practical topics include trivial events such as a drop of rain splashing into a
puddle, and the complexities of blood flowing through the heart and the flow
around a racing yacht or aerofoil.
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To understand the physics of such flows you need to model them
mathematically, and this task often presents formidable complexities. Indeed,
computational fluid mechanics is one of the prime motivators behind the building
of supercomputers.
Given this background, writing a graduate-level text on the subject is no
easy task. Two authors who share a desire to maintain mathematical rigour
without being forbidding are Ian Sobey and Stephen Pope. Happily, both
succeed.
Sobey鈥檚 Introduction to Interactive Boundary Layer Theory focuses
predominantly on classical analytical methods for analysing laminar
boundary-layer flows, which are of relevance to flows around slender and bluff
bodies. The techniques Sobey outlines are also useful for extracting major
trends without resorting to numerical simulations. The topic is intrinsically
difficult to treat well, and it is even harder to strike a balance between the
latest developments and the classical literature. Sobey refers to classical
texts, such as Horace Lamb鈥檚 1916 work on hydrodynamics, and includes material
such as the Falkner-Skan equation.
However, this is not merely a rewrite of classical topics. Sobey includes
recent work in a seamless manner to produce a very readable book. As a useful
counterweight to the trend to put less emphasis on predominantly analytical
approaches, it deserves to be a success.
Turbulent flows and their simulation fall outside the orderly world of
laminar flows, so the probabilities of events have to be calculated. One of the
strong points of Pope鈥檚 Turbulent Flows is the excellent and readable
treatment of fundamentals such as transformation properties, statistical
descriptions and scales of turbulent motion. He also clearly outlines the
derivation of the Reynolds averaged equations for the mean flow, following the
classical route of decomposing the velocity field into mean and fluctuating
(random) components. Pope carefully treats the principal difficulty of providing
models for the fluctuating terms. Pope also covers material from now classical
turbulent viscosity-based models, via Reynolds-stress closures, to large eddy
and direct numerical simulation techniques. However, the simulation of flows
with the latter technique is only a very long-term prospect due to the huge
amount of computer resources required. So the development and subsequent
application of different classes of simulation techniques is of fundamental
scientific and practical importance. The section on this topic is particularly
successful.
This is the first graduate text to cover moment-based closure approaches
alongside large eddy simulation and probability density function methods. These
approaches are increasingly important, so the section on methods based on
probability density functions would alone justify this fine book. The lucid and
up-to-date discussion鈥攚hich will appeal to researchers and engineers
alike鈥攊s a bonus.