Hendrik Tennekes

From the smallest gnat to the largest aircraft, all things that fly obey the same aerodynamic principles. The Simple Science of Flight offers a leisurely introduction to the mechanics of flight and, beyond that, to the scientific attitude that finds wonder in simple calculations, forging connections between, say, the energy efficiency of a peanut butter sandwich that fuels your body and that of the kerosene that fuels a jumbo jet. It is the product of a lifetime of watching and investigating the way flight happens. He covers paper airplanes, kites, gliders, and human-powered flying machines as well as birds and insects, explaining difficult concepts like lift, drag, wing loading, and cruising speed through many fascinating comparisons, anecdotes, and examples. Equations, often the best shorthand to explain and connect phenomena, are integrated seamlessly into the flow of the text in such a way that even math-phobic readers should not be put off. Tennekes begins with a simple comparison of the relative fuel consumption of hummingbirds, cars, and airplanes, then turns to the relations between an airplane's weight, its wing area, and its cruising speed. After showing that it is possible to collect data on all flying creatures and flying machines in a single "Great Flight Diagram", he looks at energetics through the considerable efforts of a little 35-gram bird in a wind tunnel. There are stories on the effects of headwinds, tailwinds, and weather conditions on both birds and planes, on the elegance of the mechanics that makes flight possible, and on the aerodynamics of sophisticated flying toys.

From Insects to Jumbo Jets

The Simple Science of Flight

Emeritus Professor of Aeronautical Engineering Henk Tennekes

It is the product of a lifetime of watching and investigating the way flight happens.

Scattered Showers

The Outlook

John L. Lumley

This is the first book specifically designed to offer the student a smooth transitionary course between elementary fluid dynamics (which gives only last-minute attention to turbulence) and the professional literature on turbulent flow, where an advanced viewpoint is assumed. The subject of turbulence, the most forbidding in fluid dynamics, has usually proved treacherous to the beginner, caught in the whirls and eddies of its nonlinearities and statistical imponderables. This is the first book specifically designed to offer the student a smooth transitionary course between elementary fluid dynamics (which gives only last-minute attention to turbulence) and the professional literature on turbulent flow, where an advanced viewpoint is assumed. Moreover, the text has been developed for students, engineers, and scientists with different technical backgrounds and interests. Almost all flows, natural and man-made, are turbulent. Thus the subject is the concern of geophysical and environmental scientists (in dealing with atmospheric jet streams, ocean currents, and the flow of rivers, for example), of astrophysicists (in studying the photospheres of the sun and stars or mapping gaseous nebulae), and of engineers (in calculating pipe flows, jets, or wakes). Many such examples are discussed in the book. The approach taken avoids the difficulties of advanced mathematical development on the one side and the morass of experimental detail and empirical data on the other. As a result of following its midstream course, the text gives the student a physical understanding of the subject and deepens his intuitive insight into those problems that cannot now be rigorously solved. In particular, dimensional analysis is used extensively in dealing with those problems whose exact solution is mathematically elusive. Dimensional reasoning, scale arguments, and similarity rules are introduced at the beginning and are applied throughout. A discussion of Reynolds stress and the kinetic theory of gases provides the contrast needed to put mixing-length theory into proper perspective: the authors present a thorough comparison between the mixing-length models and dimensional analysis of shear flows. This is followed by an extensive treatment of vorticity dynamics, including vortex stretching and vorticity budgets. Two chapters are devoted to boundary-free shear flows and well-bounded turbulent shear flows. The examples presented include wakes, jets, shear layers, thermal plumes, atmospheric boundary layers, pipe and channel flow, and boundary layers in pressure gradients. The spatial structure of turbulent flow has been the subject of analysis in the book up to this point, at which a compact but thorough introduction to statistical methods is given. This prepares the reader to understand the stochastic and spectral structure of turbulence. The remainder of the book consists of applications of the statistical approach to the study of turbulent transport (including diffusion and mixing) and turbulent spectra.

Hendrik Tennekes

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