Shape and Structure, from Engineering to Nature

by Adrian Bejan

• ISBN13: 9780521793889
• ISBN10: 0521793882
• Format: Paperback
• Copyright: 2000-10-16
• Publisher: Cambridge University Press

Summary

Seemingly universal geometric forms unite the flow systems of engineering and nature. For example, tree-shaped flows can be seen in computers, lungs, dendritic crystals, urban street patterns, and communication links. In this groundbreaking book, Adrian Bejan considers the design and optimization of engineered systems and discovers a deterministic principle of the generation of geometric form in natural systems. Shape and structure spring from the struggle for better performance in both engineering and nature. This idea is the basis of the new constructal theory: the objective and constraints principle used in engineering is the same mechanism from which the geometry in natural flow systems emerges. From heat exchangers to river channels, the book draws many parallels between the engineered and the natural world. Among the topics covered are mechanical structure, thermal structure, heat trees, ducts and rivers, turbulent structure, and structure in transportation and economics. The numerous illustrations, examples, and homework problems in every chapter make this an ideal text for engineering design courses. Its provocative ideas will also appeal to a broad range of readers in engineering, natural sciences, economics, and business.

Table of Contents

List of Symbols	xi
Preface	xv
Natural Form, Questioning, and Theory	1	(13)
The Great Puzzle: From What Principle can Geometric Form be Deduced?	1	(3)
The Hardest Questions	4	(2)
The Objective and Constraints Principle	6	(8)
Problems	11	(1)
References	12	(2)
Mechanical Structure	14	(15)
Cantilever Beam: Objective and Constraints	14	(2)
External Shape	16	(2)
Internal Structure	18	(2)
Shape and Structure, Together	20	(2)
Column in End Compression	22	(2)
The Concept of ``Better''	24	(5)
Problems	25	(2)
References	27	(2)
Thermal Structure	29	(23)
Cooling Electronics: Objective and Constraints	29	(1)
Volume Cooled by Natural Convection	29	(6)
Volume Cooled by Forced Convection	35	(5)
The Method of Intersecting the Asymptotes	40	(1)
The Balance between Stream-Travel Time and Diffusion Time	41	(1)
Optimal Longitudinal Flow Pulsations	42	(2)
From Constructal Principle to Internal Structure	44	(1)
Cracks in Shrinking Solids	45	(7)
Problems	49	(1)
References	50	(2)
Heat Trees	52	(30)
The Volume-to-Point Flow Problem	52	(1)
Elemental Volume	53	(3)
First Construct and Growth	56	(2)
Second and Higher-Order Constructs	58	(2)
Constructal Law	60	(2)
Tapered Channels and Optimal Angles	62	(3)
Three-Dimensional Heat Trees	65	(2)
Time-Dependent Discharge from a Volume to One Point	67	(2)
Constructal Design: Increasing Complexity in a Volume of Fixed Size	69	(5)
Design with Unrestricted Elemental Features	74	(3)
Constructal Heat Trees Are Robust	77	(5)
Problems	79	(1)
References	80	(2)
Fluid Trees	82	(35)
Bathing a Volume: Objective and Constraints	82	(2)
Elemental Volume	84	(4)
First and Higher-Order Constructs	88	(3)
Channels with Hagen-Poiseuille Flow	91	(1)
Optimization of Void-Space Distribution	92	(2)
Constructal Design: Increasing Complexity in a Volume of Fixed Size	94	(5)
Three-Dimensional Fluid Trees	99	(9)
Scaling Laws of Living Trees	108	(9)
Problems	113	(2)
References	115	(2)
Ducts and Rivers	117	(32)
Geometric Puzzles	117	(5)
Optimal River Channel Cross Sections	122	(5)
Optimal Duct Cross Sections	127	(1)
Deterministic River Drainage Basins	128	(9)
River Basins with Randomly Distributed Resistance to Erosion	137	(1)
River Basins with Optimized External Shape	137	(5)
Constructal Fluid Trees are Robust	142	(2)
Rivers of People	144	(5)
Problems	145	(2)
References	147	(2)
Turbulent Structure	149	(32)
Two Flow Regimes: High Resistance and Low Resistance, Intertwined	149	(1)
Why Do Icebergs and Logs Drift Sideways?	150	(1)
The First and Smallest Eddy	151	(6)
The Stepwise Growth of Mixing Regions	157	(1)
The Onset of Rolls in Fluid Layers Heated from Below	158	(3)
Partitioned Fluid Layer Heated from the Side	161	(2)
Optimization of Flow Geometry in Layers Heated from Below	163	(6)
Porous Layer Saturated with Fluid and Heated from Below	169	(5)
Natural Structure in Multiphase Flow Systems	174	(1)
Dendritic Crystals	175	(6)
Problems	178	(1)
References	179	(2)
Convective Trees	181	(38)
Convection in the Interstices versus Convection in the Tree Branches	181	(1)
Two-Dimensional T-Shaped Plate Fins	182	(5)
Umbrellas of Cylindrical Fins	187	(2)
Fin Trees with Optimal Plate-to-Plate Spacings	189	(9)
Trees of Circular Fins	198	(4)
Conduction in Interstitial Spaces and Convection in Channels	202	(1)
Parallel-Plate Channels	203	(5)
Optimally Tapered Parallel-Plate Channels	208	(4)
Round Tubes	212	(3)
Two Fluid Trees in Counterflow are One Tree for Convection	215	(4)
Problems	216	(2)
References	218	(1)
Structure in Power Systems	219	(27)
Allocation of Heat Exchange Inventory	220	(3)
Distribution of Insulation	223	(3)
Structure in Low-Temperature Machines	226	(4)
Streams in Counterflow	230	(4)
Flying Machines and Animals	234	(6)
Flying Carpets and Processions	240	(6)
Problems	242	(2)
References	244	(2)
Structure in time: Rhythm	246	(24)
Intermittent Heat Transfer	247	(2)
Defrosting Refrigerators	249	(3)
Cleaning Power Plants	252	(2)
Breathing	254	(3)
Heart Beating	257	(3)
The Effect of Animal Body Size	260	(10)
Problems	267	(1)
References	268	(2)
Transportation and Economics Structure	270	(30)
Minimum Travel Time	271	(7)
Minimum Cost	278	(5)
Maximum Revenue	283	(4)
Development of Economics Structure in Time	287	(1)
Optimally Shaped Triangular Areas	288	(5)
Older Methods in Spatial Economics	293	(2)
The Law of Refraction	295	(1)
The Law of Parsimony	296	(4)
Problems	297	(1)
References	298	(2)
Shapes with Constant Resistance	300	(15)
How, Not What	300	(1)
More Degrees of Freedom	301	(7)
More Efficient Structures Look More ``Natural''	308	(3)
More Material Where the Need is Greater	311	(1)
An Old and Prevalent Natural Phenomenon	312	(3)
References	314	(1)
About the Author	315	(2)
Author Index	317	(3)
Subject Index	320