Textbook
Automotive AerodynamicsISBN: 9781119185727
608 pages
July 2016, ©2016

Description
Automotive Aerodynamics
Joseph Katz, San Diego State University, USA
The automobile is an icon of modern technology because it includes most aspects of modern engineering, and it offers an exciting approach to engineering education. Of course there are many existing books on introductory fluid/aero dynamics but the majority of these are too long, focussed on aerospace and don’t adequately cover the basics. Therefore, there is room and a need for a concise, introductory textbook in this area.
Automotive Aerodynamics fulfils this need and is an introductory textbook intended as a first course in the complex field of aero/fluid mechanics for engineering students. It introduces basic concepts and fluid properties, and covers fluid dynamic equations. Examples of automotive aerodynamics are included and the principles of computational fluid dynamics are introduced. This text also includes topics such as aeroacoustics and heat transfer which are important to engineering students and are closely related to the main topic of aero/fluid mechanics.
This textbook contains complex mathematics, which not only serve as the foundation for future studies but also provide a road map for the present text. As the chapters evolve, focus is placed on more applicable examples, which can be solved in class using elementary algebra. The approach taken is designed to make the mathematics more approachable and easier to understand.
Key features:
• Concise textbook which provides an introduction to fluid mechanics and aerodynamics, with automotive applications
• Written by a leading author in the field who has experience working with motor sports teams in industry
• Explains basic concepts and equations before progressing to cover more advanced topics
• Covers internal and external flows for automotive applications
• Covers emerging areas of aeroacoustics and heat transfer
Automotive Aerodynamics is a musthave textbook for undergraduate and graduate students in automotive and mechanical engineering, and is also a concise reference for engineers in industry.
Table of Contents
Series Preface xii
Preface xiv
1 Introduction and Basic Principles 1
1.1 Introduction 1
1.2 Aerodynamics as a Subset of Fluid Dynamics 2
1.3 Dimensions and Units 3
1.4 Automobile/Vehicle Aerodynamics 5
1.5 General Features of Fluid Flow 9
1.5.1 Continuum 10
1.5.2 Laminar and Turbulent Flow 11
1.5.3 Attached and Separated Flow 12
1.6 Properties of Fluids 13
1.6.1 Density 13
1.6.2 Pressure 14
1.6.3 Temperature 14
1.6.4 Viscosity 16
1.6.5 Specific Heat 19
1.6.6 Heat Transfer Coefficient, k 19
1.6.7 Modulus of Elasticity, E 20
1.6.8 Vapor Pressure 22
1.7 Advanced Topics: Fluid Properties and the Kinetic Theory of Gases 23
1.8 Summary and Concluding Remarks 26
Reference 27
Problems 27
2 The Fluid Dynamic Equations 35
2.1 Introduction 35
2.2 Description of Fluid Motion 36
2.3 Choice of Coordinate System 38
2.4 Pathlines, Streak Lines, and Streamlines 39
2.5 Forces in a Fluid 40
2.6 Integral Form of the Fluid Dynamic Equations 43
2.7 Differential Form of the Fluid Dynamic Equations 50
2.8 The Material Derivative 57
2.9 Alternate Derivation of the Fluid Dynamic Equations 59
2.10 Example for an Analytic Solution: TwoDimensional, Inviscid Incompressible, Vortex Flow 62
2.10.1 Velocity Induced by a Straight Vortex Segment 65
2.10.2 Angular Velocity, Vorticity, and Circulation 66
2.11 Summary and Concluding Remarks 69
References 72
Problems 72
3 OneDimensional (Frictionless) Flow 81
3.1 Introduction 81
3.2 The Bernoulli Equation 82
3.3 Summary of OneDimensional Tools 84
3.4 Applications of the OneDimensional FrictionFree Flow Model 85
3.4.1 Free Jets 85
3.4.2 Examples for Using the Bernoulli Equation 89
3.4.3 Simple Models for TimeDependent Changes in a Control Volume 93
3.5 Flow Measurements (Based on Bernoulli’s Equation) 96
3.5.1 The Pitot Tube 96
3.5.2 The Venturi Tube 98
3.5.3 The Orifice 100
3.5.4 Nozzles and Injectors 101
3.6 Summary and Conclusions 102
3.6.1 Concluding Remarks 103
Problems 104
4 Dimensional Analysis, High Reynolds Number Flows, and Definition of Aerodynamics 122
4.1 Introduction 122
4.2 Dimensional Analysis of the Fluid Dynamic Equations 123
4.3 The Process of Simplifying the Governing Equations 126
4.4 Similarity of Flows 127
4.5 High Reynolds Number Flow and Aerodynamics 129
4.6 High Reynolds Number Flows and Turbulence 133
4.7 Summary and Conclusions 136
References 136
Problems 136
5 The Laminar Boundary Layer 141
5.1 Introduction 141
5.2 TwoDimensional Laminar Boundary Layer Model – The Integral Approach 143
5.3 Solutions using the von Kármán Integral Equation 147
5.4 Summary and Practical Conclusions 156
5.5 Effect of Pressure Gradient 161
5.6 Advanced Topics: The TwoDimensional Laminar Boundary Layer Equations 164
5.6.1 Summary of the Exact Blasius Solution for the Laminar Boundary Layer 167
5.7 Concluding Remarks 169
References 170
Problems 170
6 High Reynolds Number Incompressible Flow Over Bodies: Automobile Aerodynamics 176
6.1 Introduction 176
6.2 The Inviscid Irrotational Flow (and Some Math) 178
6.3 Advanced Topics: A More Detailed Evaluation of the Bernoulli Equation 181
6.4 The Potential Flow Model 183
6.4.1 Methods for Solving the Potential Flow Equations 183
6.4.2 The Principle of Superposition 184
6.5 TwoDimensional Elementary Solutions 184
6.5.1 Polynomial Solutions 185
6.5.2 TwoDimensional Source (or Sink) 187
6.5.3 TwoDimensional Doublet 190
6.5.4 TwoDimensional Vortex 193
6.5.5 Advanced Topics: Solutions Based on Green’s Identity 196
6.6 Superposition of a Doublet and a FreeStream: Flow Over a Cylinder 199
6.7 Fluid Mechanic Drag 204
6.7.1 The Drag of Simple Shapes 205
6.7.2 The Drag of More Complex Shapes 210
6.8 Periodic Vortex Shedding 215
6.9 The Case for Lift 218
6.9.1 A Cylinder with Circulation in a Free Stream 218
6.9.2 TwoDimensional Flat Plate at a Small Angle of Attack (in a Free Stream) 222
6.9.3 Note About the Center of Pressure 224
6.10 Lifting Surfaces: Wings and Airfoils 225
6.10.1 The TwoDimensional Airfoil 226
6.10.2 An Airfoil’s Lift 228
6.10.3 An Airfoil’s Drag 229
6.10.4 An Airfoil Stall 231
6.10.5 The Effect of Reynolds Number 232
6.10.6 ThreeDimensional Wings 233
6.11 Summary of High Reynolds Number Aerodynamics 248
6.12 Concluding Remarks 249
References 249
Problems 250
7 Automotive Aerodynamics: Examples 262
7.1 Introduction 262
7.2 Generic Trends (For Most Vehicles) 263
7.2.1 Ground Effect 264
7.2.2 Generic Automobile Shapes and Vortex Flows 265
7.3 Downforce and Vehicle Performance 269
7.4 How to Generate Downforce 274
7.5 Tools used for Aerodynamic Evaluations 274
7.5.1 Example for Aero Data Collection: Wind Tunnels 276
7.5.2 Wind Tunnel Wall/Floor Interference 279
7.5.3 Simulation of Moving Ground 281
7.5.4 Expected Results of CFD, Road, or Wind Tunnel Tests (and Measurement Techniques) 283
7.6 Variable (Adaptive) Aerodynamic Devices 286
7.7 Vehicle Examples 291
7.7.1 Passenger Cars 292
7.7.2 Pickup Trucks 298
7.7.3 Motorcycles 299
7.7.4 Competition Cars (Enclosed Wheel) 302
7.7.5 OpenWheel Racecars 306
7.8 Concluding Remarks 312
References 314
Problems 314
8 Introduction to Computational Fluid Mechanics (CFD) 316
8.1 Introduction 316
8.2 The FiniteDifference Formulation 317
8.3 Discretization and Grid Generation 320
8.4 The FiniteDifference Equation 321
8.5 The Solution: Convergence and Stability 324
8.6 The FiniteVolume Method 326
8.7 Example: Viscous Flow Over a Cylinder 328
8.8 PotentialFlow Solvers: Panel Methods 331
8.9 Summary 335
References 337
Problems 337
9 Viscous Incompressible Flow: “Exact Solutions” 339
9.1 Introduction 339
9.2 The Viscous Incompressible Flow Equations (Steady State) 340
9.3 Laminar Flow between Two Infinite Parallel Plates: The Couette Flow 340
9.3.1 Flow with a Moving Upper Surface 342
9.3.2 Flow between Two Infinite Parallel Plates: The Results 343
9.3.3 Flow between Two Infinite Parallel Plates – The Poiseuille Flow 347
9.3.4 The Hydrodynamic Bearing (Reynolds Lubrication Theory) 351
9.4 Flow in Circular Pipes (The HagenPoiseuille Flow) 359
9.5 Fully Developed Laminar Flow between Two Concentric Circular Pipes 364
9.6 Laminar Flow between Two Concentric, Rotating Circular Cylinders 366
9.7 Flow in Pipes: Darcy’s Formula 370
9.8 The Reynolds Dye Experiment, Laminar/Turbulent Flow in Pipes 371
9.9 Additional Losses in Pipe Flow 374
9.10 Summary of 1D Pipe Flow 375
9.10.1 Simple Pump Model 378
9.10.2 Flow in Pipes with Noncircular Cross Sections 379
9.10.3 Examples for OneDimensional Pipe Flow 381
9.10.4 Network of Pipes 391
9.11 Free Vortex in a Pool 394
9.12 Summary and Concluding Remarks 397
Reference 397
Problems 397
10 Fluid Machinery 411
10.1 Introduction 411
10.2 Work of a ContinuousFlow Machine 415
10.3 The Axial Compressor (The Mean Radius Model) 417
10.3.1 Velocity Triangles 421
10.3.2 Power and Compression Ratio Calculations 424
10.3.3 Radial Variations 429
10.3.4 Pressure Rise Limitations 431
10.3.5 Performance Envelope of Compressors and Pumps 434
10.3.6 Degree of Reaction 441
10.4 The Centrifugal Compressor (or Pump) 446
10.4.1 Torque, Power, and Pressure Rise 447
10.4.2 Impeller Geometry 450
10.4.3 The Diffuser 454
10.4.4 Concluding Remarks: Axial versus Centrifugal Design 457
10.5 Axial Turbines 458
10.5.1 Torque, Power, and Pressure Drop 459
10.5.2 Axial Turbine Geometry and Velocity Triangles 461
10.5.3 Turbine Degree of Reaction 464
10.5.4 Turbochargers (for Internal Combustion Engines) 473
10.5.5 Remarks on Exposed Tip Rotors (Wind Turbines and Propellers) 474
10.6 Concluding Remarks 478
Reference 478
Problems 478
11 Elements of Heat Transfer 485
11.1 Introduction 485
11.2 Elementary Mechanisms of Heat Transfer 486
11.2.1 Conductive Heat Transfer 486
11.2.2 Convective Heat Transfer 489
11.2.3 Radiation Heat Transfer 491
11.3 Heat Conduction 495
11.3.1 Steady OneDimensional Heat Conduction 497
11.3.2 Combined Heat Transfer 499
11.3.3 Heat Conduction in Cylinders 502
11.3.4 Cooling Fins 506
11.4 Heat Transfer by Convection 515
11.4.1 The Flat Plate Model 516
11.4.2 Formulas for Forced External Heat Convection 520
11.4.3 Formulas for Forced Internal Heat Convection 526
11.4.4 Formulas for Free (Natural) Heat Convection 529
11.5 Heat Exchangers 534
11.6 Concluding Remarks 536
References 539
Problems 539
12 Automobile AeroAcoustics 544
12.1 Introduction 544
12.2 Sound as a Pressure Wave 546
12.3 Sound Loudness Scale 549
12.4 The Human Ear Perception 552
12.5 The OneDimensional Linear Wave Equation 553
12.6 Sound Radiation, Transmission, Reflection, Absorption 556
12.6.1 Sound Wave Expansion (Radiation) 556
12.6.2 Reflections, Transmission, Absorption 559
12.6.3 Standing Wave (Resonance), Interference, and Noise Cancellations 560
12.7 Vortex Sound 561
12.8 Example: Sound from a Shear Layer 564
12.9 Buffeting 568
12.10 Experimental Examples for Sound Generation on a Typical Automobile 574
12.11 Sound and Flow Control 576
12.12 Concluding Remarks 577
References 578
Problems 578
Appendix A 581
Appendix B 583
Index 589