Pennycuick Modelling the Flying Bird

1. Auflage 2008
ISBN: 978-0-08-055781-6
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 496 Seiten

This book outlines the principles of flight, of birds in particular. It describes a way of simplifying the mechanics of flight into a practical computer program, which will predict in some detail what any bird, real or hypothetical, can and cannot do. The Flight program, presented on the companion website, generates performance curves for flapping and gliding flight, and simulations of long-distance migration and accounts successfully for the consumption of muscles and other tissues during migratory flights. The program is effectively a working model of a flying bird (or bat or pterosaur) and is the skeleton around which the book is built. The book provides a wider background and then explains how Flight works and shows how to set up and test hypotheses generated by the program.
The book and the program are based on adapting the conventional (and well-tested) thinking of aeronautical engineers to the biological problems of bird flight. Their primary aim is to convince biologists that this is the appropriate way to handle problems that involve flight, to make the engineering background accessible to biologists, and to provide a tool kit in the shape of the Flight program, which they can use to solve practical problems involving bird flight and migration. In addition, the book will be readily accessible to engineers who want to know how birds work, and should be of interest to the ever-growing community working on flapping 'micro air vehicles' (MAVs). The program can be used to predict the flight performance and capabilities of reconstructed fossil birds and pterosaurs, flying in ancient atmospheres that differ from present conditions, and also, of course, to predict and account for the results of experiments and observations on living birds and bats.
* An up to date work by the world's leading expert on bird flight
* Examines the biology and biomechanics of bird flight with added reference to the flight of bats and pterosaurs.
* Uses proven aeronautical principles to help solve biological issues in understanding and predicting the flight capabilities of birds and other vertebrates.
* Provides insights into the evolution of flight and the likely capabilities of extinct birds and reptiles.
* Gives a detailed explanation of the science behind, and use of, the author's predictive bird flight simulation program - Flight - which is available on a companion website.
* Presents often difficult concepts in easily understood language.

Autoren/Hrsg.

Pennycuick, C. J.

Inhaltsverzeichnis

1;Front Cover;1
2;Modelling the Flying Bird;4
3;Front Cover;1
4;Copyright Page;5
5;Contents;6
6;Preface;10
7;Foreword;12
8;Acknowledgements;14
9;Chapter 1: Background to the Model;16
9.1;1.1. The Flight Model;17
9.2;1.2. The Engineering Approach to Numbers;30
9.3;1.3. Dimensions and Units;33
9.4;1.4. Literature Citations;35
10;Chapter 2: The Flight Environment;36
10.1;2.1. The Earth's Gravity Field;37
10.2;2.2. The Earth's Atmosphere;39
10.3;2.3. Air Density in flight;46
10.4;2.4. Gravity and the Atmosphere in Former Times;47
11;Chapter 3: Mechanics of Level Flight;52
11.1;3.1. Power Required for Horizontal Flight;53
11.2;3.2. The Power Curve Calculation in Flight;61
11.3;3.3. Significance of the Characteristic Speeds;78
11.4;3.4. Effect of Air Density on Speed and Power;81
11.5;3.5. Adaptive Significance of Morphology;83
11.6;3.6. Two-Dimensional Aerofoil Properties;84
11.7;3.7. Scale and Reynolds Number;93
12;Chapter 4: Vortices and Vortex Wakes;94
12.1;4.1. The Concept of the Line Vortex;95
12.2;4.2. Vortex Concepts Applied to Fixed Wings;96
12.3;4.3. Lifting-Line Theory Applied to Flapping Wings;106
12.4;4.4. Wind Tunnel Studies of Bird Wakes;108
12.5;4.5. Feathered Wings;117
13;Chapter 5: The Feathered Wings of Birds;120
13.1;5.1. General Structural Requirements;121
13.2;5.2. Mechanics of the Bird Wing;134
13.3;5.3. Flapping the Wings;143
13.4;5.4. The Rest of the Skeleton;145
13.5;5.5. Adaptations for Gliding;148
14;Chapter 6: The Membrane Wings of Bats and Pterosaurs;150
14.1;6.1. Bats;151
14.2;6.2. Pterosaurs;164
15;Chapter 7: Muscles as Engines;176
15.1;7.1. General Requirements;178
15.2;7.2. The Sliding Filament Engine;179
15.3;7.3. Muscle Performance in Locomotion;184
15.4;7.4. Adaptations for Aerobic Flight;209
16;Chapter 8: Simulating Long-Distance Migration;224
16.1;8.1. Estimating Range;225
16.2;8.2. Ultra Long-Distance Migrants;228
16.3;8.3. The Concept of Energy Height;242
16.4;8.4. Effect of Flying Height on Range;254
16.5;8.5. Aerobic Capacity and Climb;255
16.6;8.6. Basal Metabolism;256
16.7;8.7. Water Economy;258
16.8;8.8. Sleep;259
17;Chapter 9: Accelerated Flight and Manoeuvring;260
17.1;9.1. Intermittent Flight Styles in Flapping Flight;261
17.2;9.2. Manoeuvring Frame of Reference: Flight Controls;268
17.3;9.3. Transient Manoeuvres;283
18;Chapter 10: Gliding Flight and Soaring;286
18.1;10.1. Gliding Performance;287
18.2;10.2. Soaring;295
19;Chapter 11: Information Systems For Flying Animals;320
19.1;11.1. Senses;324
19.2;11.2. Orientation and Navigation;335
20;Chapter 12: Water Birds;348
20.1;12.1. Waterproofing and Thermal Insulation;349
20.2;12.2. Mechanics of Swimming;350
20.3;12.3. Morphological Trends in Waterbirds;358
20.4;12.4. Other Aquatic Adaptations;362
21;Chapter 13: Allometry;366
21.1;13.1. Allometry of Morphological Variables;368
21.2;13.2. Allometry of Calculated Variables;379
21.3;13.3. Variations on Allometry;389
22;Chapter 14: Wind Tunnel Experiments With Birds And Bats;392
22.1;14.1. Wind Tunnel Basics;393
22.2;14.2. Wind Tunnel Layouts;394
22.3;14.3. Wind Tunnel Components and Their Functions;397
22.4;14.4. Birds in Wind Tunnels;409
23;Chapter 15: Theory As The Basis For Observation;424
23.1;15.1. Flight Speed Measurements;425
23.2;15.2. Wind Tunnel Results Related to Field Studies;443
23.3;15.3. Wingbeat Frequency;450
23.4;15.4. The Theoretical Backbone;454
24;Chapter 16: Evolution of Flight;458
24.1;16.1. Evolution in Engineering and in Nature;459
24.2;16.2. Past the Squirrel Barrier;466
24.3;16.3. Evolution of the Bird Wing;469
24.4;16.4. Adding an Engine;474
24.5;16.5. Size Restrictions;475
24.6;16.6. Time Scale of Evolution;476
25;References;478
26;Index;486

Leseproben

Chapter 2 The Flight Environment C.J. Pennycuick Abstract The two most important environmental quantities for flight calculations are the strength of gravity and the density of the air, neither of which is routinely recorded in traditional biological investigations. This chapter outlines the properties of the earth's gravity field and atmosphere, gives practical methods for estimating the air density at the bird's flying height, and introduces the properties, uses and limitations of the fictional International Standard Atmosphere. If the flight environment has changed over geological time, this would affect the interpretation of fossil flying animals. A bird's flight performance is affected by the chemical composition, humidity and temperature of the air in which it flies, but these effects are physiological, and are not covered by the Flight program. Flight deals with the physics of flight, and it requires values for just two environmental variables, neither of which is routinely recorded by physiologists or ecologists. These are the strength of gravity and the air density. Flying would be a very different proposition on either of our planetary neighbours Mars and Venus, even if they had oxygen in their atmospheres and benign temperatures, and were able to support life. Both have weaker gravity than ours, which reduces the weight for a given mass, and also the energetic cost of supporting it. Flying would be slow on Venus, and cheap in terms of power, because the atmosphere is two orders of magnitude denser than ours, but fast and expensive on Mars, because the atmosphere there is two orders of magnitude less dense than ours. Here on Earth, gravity is nearly constant, anywhere that a bird is likely to go, but the density of the air varies wildly from place to place, from day to day and (especially) at different heights above sea level. 2.1 The Earth's Gravity Field
The Newtonian view of gravity is sufficient for flight performance calculations. It says that the earth exerts a force on the apple (its weight) which is proportional to the product of the mass of the earth and that of the apple, and inversely proportional to the square of the distance between their centres of mass. The weight force actually attracts the earth to the apple as well as vice versa, but since the earth is much more massive than the apple, we perceive this mutual attraction as a force that causes the apple to accelerate, if dropped, towards the earth. The weight of a meteorite of constant mass (i.e., not burning up) increases as it falls in from space because it is getting nearer to the centre of the earth, and reaches a maximum value at the surface. If it happens to fall down a mine shaft, its weight starts to decrease, because some of the earth's mass is now attracting it from above. Since different objects experience weights proportional to their masses, all experience the same acceleration in free fall, relative to the earth, at the same point in the gravity field. This acceleration due to gravity is used as the measure of the strength of gravity. The earth's gravity at the surface is strongest at the poles and weakest at the equator, for two reasons. In the first place, the earth's radius is greater at the equator, and an object at the surface there is further away from the earth's centre than it would be at the poles. Secondly, the rotation of the earth forces an object on the surface to accelerate towards the earth's centre, thereby reducing its weight. This centripetal effect is strongest at the equator, and dwindles to nothing at the poles. The effects of latitude and height on gravity are combined empirically in Helmert's equation (Box 2.1, Table 2.1). At any latitude, the earth's gravity decreases with height above sea level. Taking the effects of latitude and height together, the acceleration due to gravity varies from 9.83 m s-2 at sea level at the poles, down to 9.75 m s-2 at a height of 10,000 m above sea level over the equator (Table 2.1). Small “gravity anomalies” are superimposed on this underlying gravity distribution, due to density variations in the earth's mantle and crust. It is usually assumed that gravity was much the same in past ages as it is now, although it is not clear that the average density of the mantle has always been the same as it is now. If the mantle were to expand, surface gravity would decrease without any change in the earth's mass, and if it did that in mesozoic times, the existence of very large dinosaurs and pterosaurs would be easier to understand (Box 2.4). The default value used for gravity in Flight is 9.81 m s-2, and this will usually be within half of one per cent of the present value of gravity, anywhere that a bird is likely to go. The value of gravity in the programme can be changed by the user, but this is intended for simulating flight on other planets, or on earth at past or future times, rather than for refining the present value of gravity at particular points. Box 2.1 The earth's gravity Helmert's equation is a polynomial expression which gives an approximation to the acceleration due to gravity (g) in m s-2, as a function of latitude (L) and height (h) in metres above mean sea level:

Values of g from this formula are tabulated in Table 2.1 for latitudes from 0 to 90 degrees (either north or south), and heights up to 10,000 m above sea level, which is near the top of the troposphere, and higher than any bird is known to fly. The formula allows for the earth's angular velocity and ellipsoidal shape, but not for gravity anomalies due to topography, or variations of density in the mantle and crust. Table 2.1 Earth's surface gravity. Acceleration due to gravity in m s-2 from Helmert's equation. Box 2.4 Constancy of the flight environment The two environmental variables that occur in the equations for speed and power (Chapter 3) are the acceleration due to gravity and the air density. It is often assumed (explicitly or not) in discussions of the flight performance of fossil flying animals that the strength of gravity and the air density were the same when those creatures lived as they are now. This raises some difficulties in the case of flying animals that were bigger than any living birds, namely, the larger Cretaceous pterodactyls (Chapter 6, Section 6.2.5) and the giant Miocene bird Argentavis, as scaling considerations indicate that there is an upper limit to the size and mass of an animal that can maintain height by muscle power (Chapter 7, Box 7.4). Also, it seems that present-day swans are very near that limit (Chapter 7, Box 7.5). The favoured explanation for still larger flying fossil animals is that they must have been incapable of level flight, and therefore dependant on soaring. However, if the air density were higher in ancient times than it is now, or the strength of gravity lower, or both, the difficulty would be reduced, and might disappear altogether. Is this possible? Variable definitions for this box
G Newton's gravitational constant g Acceleration due to gravity at the earth's surface m Mass of a small body resting on the earth's surface ma Mass of the earth's atmosphere me Mass of a spherical earth p0 Atmospheric pressure at sea level R Gas constant re Radius of a spherical earth Se Surface area of a spherical earth T Absolute temperature W Weight of a small body resting on the earth's surface ?e Mean density of the earth ?0 Air density at sea level The mass of the earth is constant
Particles of dust fall into the earth's atmosphere every day from space, sometimes making visible trails as they burn up (meteors). Larger objects (meteorites) reach the surface and produce craters, and a few are large enough to cause widespread devastation on the scale that wiped out the dinosaurs. Kyte and Wasson (1986) estimated that all of these different-sized objects together increase the earth's mass by around 78 million kilograms per year on average, and that this rate has not varied much over past intervals of tens of millions of years. If we go back 100 million years into the Mesozoic, then the earth's mass would have increased by about 8 × 1015 kg since then, according to this estimate. However, as the earth's present mass is just under 6 × 1024 kg, or 109 times the estimated amount added in the last 100 million years, it is safe to say that the accretion of mass has been negligible for all practical purposes, throughout the time when there have been flying animals. The earth's mass may be considered constant at 5.976 × 1024 kg (Beatty et al. 1981). Radius of the earth and surface gravity
Constant earth mass does not...