Much-needed, fresh approach that brings a greater insight into the physical understanding of aerodynamics Based on the author&;s decades of industrial experience with Boeing, this book helps students and practicing engineers to gain a greater physical understanding of aerodynamics. Relying on clear physical arguments and examples, Mclean provides a much-needed, fresh approach to this sometimes contentious subject without shying away from addressing "real" aerodynamic situations as opposed to the oversimplified ones frequently used for mathematical convenience. Motivated by the belief that engineering practice is enhanced in the long run by a robust understanding of the basics as well as real cause-and-effect relationships that lie behind the theory, he provides intuitive physical interpretations and explanations, debunking commonly-held misconceptions and misinterpretations, and building upon the contrasts provided by wrong explanations to strengthen understanding of the right ones.
- Provides a refreshing view of aerodynamics that is based on the author&;s decades of industrial experience yet is always tied to basic fundamentals.
- Provides intuitive physical interpretations and explanations, debunking commonly-held misconceptions and misinterpretations
- Offers new insights to some familiar topics, for example, what the Biot-Savart law really means and why it causes so much confusion, what &;Reynolds number&; and &;incompressible flow&; really mean, and a real physical explanation for how an airfoil produces lift.
- Addresses "real" aerodynamic situations as opposed to the oversimplified ones frequently used for mathematical convenience, and omits mathematical details whenever the physical understanding can be conveyed without them.
Foreword xi Series Preface xiii Preface xv List of Symbols xix 1
Introduction to the Conceptual Landscape 1 2 From Elementary Particles to
Aerodynamic Flows 5 3 Continuum Fluid Mechanics and the Navier-Stokes
Equations 13 3.1 The Continuum Formulation and Its Range of Validity 13
3.2 Mathematical Formalism 16 3.3 Kinematics: Streamlines, Streaklines,
Timelines, and Vorticity 18 3.3.1 Streamlines and Streaklines 18 3.3.2
Streamtubes, Stream Surfaces, and the Stream Function 19 3.3.3 Timelines 22
3.3.4 The Divergence of the Velocity and Green's Theorem 23 3.3.5 Vorticity
and Circulation 24 3.3.6 The Velocity Potential in Irrotational Flow 26
3.3.7 Concepts that Arise in Describing the Vorticity Field 26 3.3.8
Velocity Fields Associated with Concentrations of Vorticity 29 3.3.9 The
Biot-Savart Law and the "Induction" Fallacy 31 3.4 The Equations of Motion
and their Physical Meaning 33 3.4.1 Continuity of the Flow and Conservation
of Mass 34 3.4.2 Forces on Fluid Parcels and Conservation of Momentum 35
3.4.3 Conservation of Energy 36 3.4.4 Constitutive Relations and Boundary
Conditions 37 3.4.5 Mathematical Nature of the Equations 37 3.4.6 The
Physics as Viewed in the Eulerian Frame 38 3.4.7 The Pseudo-Lagrangian
Viewpoint 40 3.5 Cause and Effect, and the Problem of Prediction 40 3.6 The
Effects of Viscosity 43 3.7 Turbulence, Reynolds Averaging, and Turbulence
Modeling 48 3.8 Important Dynamical Relationships 55 3.8.1 Galilean
Invariance, or Independence of Reference Frame 55 3.8.2 Circulation
Preservation and the Persistence of Irrotationality 56 3.8.3 Behavior of
Vortex Tubes in Inviscid and Viscous Flows 57 3.8.4 Bernoulli Equations and
Stagnation Conditions 58 3.8.5 Crocco's Theorem 60 3.9 Dynamic Similarity
60 3.9.1 Compressibility Effects and the Mach Number 63 3.9.2 Viscous
Effects and the Reynolds Number 63 3.9.3 Scaling of Pressure Forces: the
Dynamic Pressure 64 3.9.4 Consequences of Failing to Match All of the
Requirements for Similarity 65 3.10 "Incompressible" Flow and Potential Flow
66 3.11 Compressible Flow and Shocks 70 3.11.1 Steady 1D Isentropic Flow
Theory 71 3.11.2 Relations for Normal and Oblique Shock Waves 74 4
Boundary Layers 79 4.1 Physical Aspects of Boundary-Layer Flows 80 4.1.1
The Basic Sequence: Attachment, Transition, Separation 80 4.1.2 General
Development of the Boundary-Layer Flowfield 82 4.1.3 Boundary-Layer
Displacement Effect 90 4.1.4 Separation from a Smooth Wall 93 4.2
Boundary-Layer Theory 99 4.2.1 The Boundary-Layer Equations 100 4.2.2
Integrated Momentum Balance in a Boundary Layer 108 4.2.3 The Displacement
Effect and Matching with the Outer Flow 110 4.2.4 The Vorticity "Budget" in
a 2D Incompressible Boundary Layer 113 4.2.5 Situations That Violate the
Assumptions of Boundary-Layer Theory 114 4.2.6 Summary of Lessons from
Boundary-Layer Theory 117 4.3 Flat-Plate Boundary Layers and Other
Simplified Cases 117 4.3.1 Flat-Plate Flow 117 4.3.2 2D Boundary-Layer
Flows with Similarity 121 4.3.3 Axisymmetric Flow 123 4.3.4
Plane-of-Symmetry and Attachment-Line Boundary Layers 125 4.3.5 Simplifying
the Effects of Sweep and Taper in 3D 128 4.4 Transition and Turbulence 130
4.4.1 Boundary-Layer Transition 131 4.4.2 Turbulent Boundary Layers 138 4.5
Control and Prevention of Flow Separation 150 4.5.1 Body Shaping and
Pressure Distribution 150 4.5.2 Vortex Generators 150 4.5.3 Steady
Tangential Blowing through a Slot 155 4.5.4 Active Unsteady Blowing 157
4.5.5 Suction 157 4.6 Heat Transfer and Compressibility 158 4.6.1 Heat
Transfer, Compressibility, and the Boundary-Layer Temperature Field 158
4.6.2 The Thermal Energy Equation and the Prandtl Number 159 4.6.3 The Wall
Temperature and Other Relations for an Adiabatic Wall 159 4.7 Effects of
Surface Roughness 162 5 General Features of Flows around Bodies 163 5.1
The Obstacle Effect 164 5.2 Basic Topology of Flow Attachment and Separation
168 5.2.1 Attachment and Separation in 2D 169 5.2.2 Attachment and
Separation in 3D 171 5.2.3 Streamline Topology on Surfaces and in Cross
Sections 176 5.3 Wakes 186 5.4 Integrated Forces: Lift and Drag 189 6
Drag and Propulsion 191 6.1 Basic Physics and Flowfield Manifestations of
Drag and Thrust 192 6.1.1 Basic Physical Effects of Viscosity 193 6.1.2 The
Role of Turbulence 193 6.1.3 Direct and Indirect Contributions to the Drag
Force on the Body 194 6.1.4 Determining Drag from the Flowfield: Application
of Conservation Laws 196 6.1.5 Examples of Flowfield Manifestations of Drag
in Simple 2D Flows 204 6.1.6 Pressure Drag of Streamlined and Bluff Bodies
207 6.1.7 Questionable Drag Categories: Parasite Drag, Base Drag, and Slot
Drag 210 6.1.8 Effects of Distributed Surface Roughness on Turbulent Skin
Friction 212 6.1.9 Interference Drag 222 6.1.10 Some Basic Physics of
Propulsion 225 6.2 Drag Estimation 241 6.2.1 Empirical Correlations 242
6.2.2 Effects of Surface Roughness on Turbulent Skin Friction 243 6.2.3 CFD
Prediction of Drag 250 6.3 Drag Reduction 250 6.3.1 Reducing Drag by
Maintaining a Run of Laminar Flow 251 6.3.2 Reduction of Turbulent Skin
Friction 251 7 Lift and Airfoils in 2D at Subsonic Speeds 259 7.1
Mathematical Prediction of Lift in 2D 260 7.2 Lift in Terms of Circulation
and Bound Vorticity 265 7.2.1 The Classical Argument for the Origin of the
Bound Vorticity 267 7.3 Physical Explanations of Lift in 2D 269 7.3.1 Past
Explanations and their Strengths and Weaknesses 269 7.3.2 Desired Attributes
of a More Satisfactory Explanation 284 7.3.3 A Basic Explanation of Lift on
an Airfoil, Accessible to a Nontechnical Audience 286 7.3.4 More Physical
Details on Lift in 2D, for the Technically Inclined 302 7.4 Airfoils 307
7.4.1 Pressure Distributions and Integrated Forces at Low Mach Numbers 307
7.4.2 Profile Drag and the Drag Polar 316 7.4.3 Maximum Lift and
Boundary-Layer Separation on Single-Element Airfoils 319 7.4.4 Multielement
Airfoils and the Slot Effect 329 7.4.5 Cascades 335 7.4.6 Low-Drag Airfoils
with Laminar Flow 338 7.4.7 Low-Reynolds-Number Airfoils 341 7.4.8 Airfoils
in Transonic Flow 342 7.4.9 Airfoils in Ground Effect 350 7.4.10 Airfoil
Design 352 7.4.11 Issues that Arise in Defining Airfoil Shapes 354 8 Lift
and Wings in 3D at Subsonic Speeds 359 8.1 The Flowfield around a 3D Wing
359 8.1.1 General Characteristics of the Velocity Field 359 8.1.2 The
Vortex Wake 362 8.1.3 The Pressure Field around a 3D Wing 371 8.1.4
Explanations for the Flowfield 371 8.1.5 Vortex Shedding from Edges Other
Than the Trailing Edge 375 8.2 Distribution of Lift on a 3D Wing 376 8.2.1
Basic and Additional Spanloads 376 8.2.2 Linearized Lifting-Surface Theory
379 8.2.3 Lifting-Line Theory 380 8.2.4 3D Lift in Ground Effect 382 8.2.5
Maximum Lift, as Limited by 3D Effects 384 8.3 Induced Drag 385 8.3.1 Basic
Scaling of Induced Drag 385 8.3.2 Induced Drag from a Farfield Momentum
Balance 386 8.3.3 Induced Drag in Terms of Kinetic Energy and an Idealized
Rolled-Up Vortex Wake 389 8.3.4 Induced Drag from the Loading on the Wing
Itself: Trefftz-Plane Theory 391 8.3.5 Ideal (Minimum) Induced-Drag Theory
394 8.3.6 Span-Efficiency Factors 396 8.3.7 The Induced-Drag Polar 397
8.3.8 The Sin-Series Spanloads 398 8.3.9 The Reduction of Induced Drag in
Ground Effect 401 8.3.10 The Effect of a Fuselage on Induced Drag 402
8.3.11 Effects of a Canard or Aft Tail on Induced Drag 404 8.3.12 Biplane
Drag 409 8.4 Wingtip Devices 411 8.4.1 Myths Regarding the Vortex Wake, and
Some Questionable Ideas for Wingtip Devices 411 8.4.2 The Facts of Life
Regarding Induced Drag and Induced-Drag Reduction 414 8.4.3 Milestones in
the Development of Theory and Practice 420 8.4.4 Wingtip Device Concepts 422
8.4.5 Effectiveness of Various Device Configurations 423 8.5 Manifestations
of Lift in the Atmosphere at Large 427 8.5.1 The Net Vertical Momentum
Imparted to the Atmosphere 427 8.5.2 The Pressure Far above and below the
Airplane 429 8.5.3 Downwash in the Trefftz Plane and Other
Momentum-Conservation Issues 431 8.5.4 Sears's Incorrect Analysis of the
Integrated Pressure Far Downstream 435 8.5.5 The Real Flowfield Far
Downstream of the Airplane 436 8.6 Effects of Wing Sweep 444 8.6.1 Simple
Sweep Theory 444 8.6.2 Boundary Layers on Swept Wings 449 8.6.3
Shock/Boundary-Layer Interaction on Swept Wings 464 8.6.4
Laminar-to-Turbulent Transition on Swept Wings 465 8.6.5 Relating a Swept,
Tapered Wing to a 2D Airfoil 468 8.6.6 Tailoring of the Inboard Part of a
Swept Wing 469 9 Theoretical Idealizations Revisited 471 9.1
Approximations Grouped According to how the Equations were Modified 471
9.1.1 Reduced Temporal and/or Spatial Resolution 472 9.1.2 Simplified
Theories Based on Neglecting Something Small 472 9.1.3 Reductions in
Dimensions 472 9.1.4 Simplified Theories Based on Ad hoc Flow Models 472
9.1.5 Qualitative Anomalies and Other Consequences of Approximations 481 9.2
Some Tools of MFD (Mental Fluid Dynamics) 482 9.2.1 Simple Conceptual Models
for Thinking about Velocity Fields 482 9.2.2 Thinking about Viscous and
Shock Drag 485 9.2.3 Thinking about Induced Drag 486 9.2.4 A Catalog of
Fallacies 487 10 Modeling Aerodynamic Flows in Computational Fluid Dynamics
491 10.1 Basic Definitions 493 10.2 The Major Classes of CFD Codes and
Their Applications 493 10.2.1 Navier-Stokes Methods 493 10.2.2 Coupled
Viscous/Inviscid Methods 497 10.2.3 Inviscid Methods 498 10.2.4 Standalone
Boundary-Layer Codes 501 10.3 Basic Characteristics of Numerical Solution
Schemes 501 10.3.1 Discretization 501 10.3.2 Spatial Field Grids 502
10.3.3 Grid Resolution and Grid Convergence 506 10.3.4 Solving the
Equations, and Iterative Convergence 507 10.4 Physical Modeling in CFD 508
10.4.1 Compressibility and Shocks 508 10.4.2 Viscous Effects and Turbulence
510 10.4.3 Separated Shear Layers and Vortex Wakes 511 10.4.4 The Farfield
513 10.4.5 Predicting Drag 514 10.4.6 Propulsion Effects 515 10.5 CFD
Validation? 515 10.6 Integrated Forces and the Components of Drag 516 10.7
Solution Visualization 517 10.8 Things a User Should Know about a CFD Code
before Running it 524 References 527 Index 539
