ISBN-10:
1119967511
ISBN-13:
9781119967514
Pub. Date:
12/26/2012
Publisher:
Wiley
Understanding Aerodynamics: Arguing from the Real Physics / Edition 1

Understanding Aerodynamics: Arguing from the Real Physics / Edition 1

by Doug McLean

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Product Details

ISBN-13: 9781119967514
Publisher: Wiley
Publication date: 12/26/2012
Series: Aerospace Series
Pages: 576
Sales rank: 443,602
Product dimensions: 6.90(w) x 9.90(h) x 1.20(d)

About the Author

Doug Mclean, Boeing Commercial Airplanes, USA
Doug McLean is a Boeing Technical Fellow in the Enabling Technology and Research unit within Aerodynamics Engineering at Boeing Commercial Airplanes.? He received a BA in physics from the University of California at Riverside in 1965 and a PhD in aeronautical engineering from Princeton University in 1970. He joined the Boeing Commercial Airplane Group in 1974 and has worked there ever since on a range of problems, both computational and experimental, in the areas of viscous flow, drag reduction, and aerodynamic design. Computer programs he developed for the calculation of three-dimensional boundary layers and swept shock/boundary-layer interactions were in use by wing-design groups at Boeing for many years.

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Table of Contents

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 Equations13

3.1 The Continuum Formulation and Its Range of Validity 13

3.2 Mathematical Formalism 16

3.3 Kinematics: Streamlines, Streaklines, Timelines, andVorticity 18

3.3.1 Streamlines and Streaklines 18

3.3.2 Streamtubes, Stream Surfaces, and the Stream Function19

3.3.3 Timelines 22

3.3.4 The Divergence of the Velocity and Green’s Theorem23

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 Field26

3.3.8 Velocity Fields Associated with Concentrations ofVorticity 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 Momentum35

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 Modeling48

3.8 Important Dynamical Relationships 55

3.8.1 Galilean Invariance, or Independence of Reference Frame55

3.8.2 Circulation Preservation and the Persistence ofIrrotationality 56

3.8.3 Behavior of Vortex Tubes in Inviscid and Viscous Flows57

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 Requirementsfor 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, Separation80

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 Flow110

4.2.4 The Vorticity “Budget” in a 2D IncompressibleBoundary Layer 113

4.2.5 Situations That Violate the Assumptions of Boundary-LayerTheory 114

4.2.6 Summary of Lessons from Boundary-Layer Theory 117

4.3 Flat-Plate Boundary Layers and Other Simplified Cases117

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 Layers125

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-LayerTemperature 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 AdiabaticWall 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 Sections176

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 andThrust 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 theBody 194

6.1.4 Determining Drag from the Flowfield: Application ofConservation Laws 196

6.1.5 Examples of Flowfield Manifestations of Drag in Simple 2DFlows 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 SkinFriction 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 Friction243

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 BoundVorticity 267

7.3 Physical Explanations of Lift in 2D 269

7.3.1 Past Explanations and their Strengths and Weaknesses269

7.3.2 Desired Attributes of a More Satisfactory Explanation284

7.3.3 A Basic Explanation of Lift on an Airfoil, Accessible to aNontechnical Audience 286

7.3.4 More Physical Details on Lift in 2D, for the TechnicallyInclined 302

7.4 Airfoils 307

7.4.1 Pressure Distributions and Integrated Forces at Low MachNumbers 307

7.4.2 Profile Drag and the Drag Polar 316

7.4.3 Maximum Lift and Boundary-Layer Separation onSingle-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 Edge375

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 IdealizedRolled-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 QuestionableIdeas for Wingtip Devices 411

8.4.2 The Facts of Life Regarding Induced Drag and Induced-DragReduction 414

8.4.3 Milestones in the Development of Theory and Practice420

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 Atmosphere427

8.5.2 The Pressure Far above and below the Airplane 429

8.5.3 Downwash in the Trefftz Plane and OtherMomentum-Conservation Issues 431

8.5.4 Sears’s Incorrect Analysis of the IntegratedPressure 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 wereModified 471

9.1.1 Reduced Temporal and/or Spatial Resolution 472

9.1.2 Simplified Theories Based on Neglecting Something Small472

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 ofApproximations 481

9.2 Some Tools of MFD (Mental Fluid Dynamics) 482

9.2.1 Simple Conceptual Models for Thinking about VelocityFields 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 Dynamics491

10.1 Basic Definitions 493

10.2 The Major Classes of CFD Codes and Their Applications493

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 Runningit 524

References 527

Index 539

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