Automotive Aerodynamics

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 must–have textbook for undergraduate and graduate students in automotive and mechanical engineering, and is also a concise reference for engineers in industry.

Preface

Chapter 1: Basic Concepts and Fluid Properties

1.1 Introduction

1.2 Aerodynamics as a subset of fluid dynamics

1.3 Dimensions and units

1.4 Automobile/Vehicle aerodynamics

1.5 General features of fluid flow

1.5.1 Continuum

1.5.2 Laminar and turbulent flow

1.5.3 Attached and separated flow

1.6 Properties of fluids

1.7 Advanced Topics: Fluid properties and the kinetic theory of gases

1.8 Summary and Concluding Remarks

Chapter 2: The Fluid Dynamic Equations

2.1 Introduction

2.2 Description of Fluid Motion

2.3 Choice of Coordinate System

2.4 Pathlines, Streak Lines, and Streamlines

2.5 Forces in a Fluid

2.6 Integral Form of the Fluid Dynamic Equations

2.7 Differential Form of the Fluid Dynamic Equations

2.8 The material derivative

2.9 Alternate Derivation of the Fluid Dynamic Equations

2.10 Example for an Analytic Solution: 2D Inviscid incompressible Vortex Flow

2.10.1 Angular Velocity, Vorticity and Circulation

2.11 Summary and Concluding Remarks

Chapter 3: One–Dimensional (Frictionless) Flow

3.1 Introduction

3.2 The Bernoulli Equation

3.3. Summary of the one–dimensional tools

3.4 Applications of the One–Dimensional Flow Model

3.4.1 Free Jets

3.4.2 Examples for Using the Bernoulli Equation

3.4.3 Simple Models for Time Dependent Changes in a Control Volume

3.5 Flow Measurements (Based on Bernoulli s Equation)

3.5.1 The Pitot Tube

3.5.2 The Venturi Tube

3.5.3 The Orifice

3.5.4 Nozzles and Injectors

3.6 Summary and Conclusions

3.6.1. Concluding Remarks

Chapter 4: Dimensional Analysis, High Reynolds Number Flows, and the Definition of Aerodynamics.

4.1 Introduction

4.2 Dimensional Analysis of the Fluid Dynamic Equations

4.3. The process of Simplifying the Governing Equations

4.4 Similarity of Flows

4.5 High Reynolds Number Flow and Aerodynamics

4.6 High Reynolds Number Flows and Turbulence

4.7 Summary and Conclusions

Chapter 5: THE LAMINAR BOUNDARY LAYER

5.1 Introduction

5.2 Two–Dimensional Laminar Boundary Layer Model The Integral Approach

5.3 Solutions Using the von Kármán Integral Equation

5.4 Summary and Practical Conclusions

5.5 Effect of Pressure Gradient

5.6 Advanced Topics: The Two Dimensional Boundary Layer Equations

5.6.1 Summary of the Blasius Exact Solution for the Laminar Boundary Layer

5.7 Concluding Remarks

Chapter 6: High Reynolds Number (Incompressible) Flow Over Bodies

6.1 Introduction

6.2 The Inviscid Irrotational Flow (and some Math)

6.3 Advanced topics: A more detailed evaluation of the Bernoulli Equation

6.4 The Potential Flow Model

6.4.1 Methods for solving the potential flow equations

6.4.2 The Principle of Superposition

6.5 Two–Dimensional Elementary Solutions

6.5.1 Polynomial solution

6.5.2 Two–Dimensional Source (or sink).

6.5.3 Two–Dimensional Doublet

6.5.4 Two–Dimensional Vortex

6.5.5 Advanced Topics: Solutions based on Green s Identity

6.6 Superposition of a Doublet and a Free–Stream: Flow Over a Cylinder

6.7 Fluid Mechanic Drag

6.7.1 The Drag of Simple Shapes

6.7.2 The Drag of More Complex Shapes

6.8 Periodic Vortex Shedding

6.9 The case for Lift

6.9.1 Rotating cylinder in a free–stream

6.9.2 Flat plate at an angle of attack in a free–stream

6.9.3 Note about the Center of Pressure

6.10 Lifting Surfaces: Wings and Airfoils

6.10.1 The two–dimensional airfoil

6.10.2 An Airfoil s Lift

6.10.3 An Airfoil s Drag

6.10.4 An Airfoil s Stall

6.10.5 The Effect of Reynolds Number

6.10.6 Three–Dimensional Wings

6.11 Summary and Concluding Remarks

Chapter 7: Automotive Aerodynamics: Examples

7.1 Introduction

7.2 Generic Trends (for most vehicles)

7.2.1 Ground effect

7.2.2 Generic Automobile Shapes and Vortex Flow

7.3 Downforce and Vehicle Performance

7.4 How to Generate Downforce

7.5 Tools used for aerodynamic evaluation

7.5.1 Example for Aero Data Collection: wind tunnels

7.5.2 Wind Tunnel Wall/Floor interference

7.5.3 Expected Results of CFD, Road or Wind Tunnel Tests

7.6 Variable (Adaptive) Aerodynamic Devices

7.7 Vehicle Examples

7.7.1 Passenger cars

7.7.2 Pick Up Trucks

7.7.3. Motorcycles

7.7.4 Competition cars (enclosed wheel)

7.7.5 Open wheel racecars

7.8 Concluding Remarks

Chapter 8: Introduction to Computational Fluid Mechanics (CFD)

8.1 Introduction

8.2 The Finite Difference Formulation

8.3 Discretization and grid generation

8.4 The Finite Difference Equation

8.5 The Solution: Convergence and Stability

8.6 The Finite Volume Method

8.7 Example: Viscous Flow over a Cylinder

8.8 Potential–Flow Solvers: Panel Methods

8.7 Summary

Chapter 9: Viscous (Laminar) Incompressible Flow: Exact Solutions

9.1 Introduction

9.2 The viscous incompressible flow equations (steady state)

9.3 Flow between two infinite parallel plates The Couette flow

9.3.1 Flow with a moving upper surface

9.3.2 Flow between two infinite parallel plates The Results

9.3.3 Flow between two infinite parallel plates The Poiseuille flow

9.3.4 The Hydrodynamic Bearing (Reynolds Lubrication Theory)

9.4 Flow in Circular Pipes (The Hagen–Poiseuille Flow)

9.5 Fully developed laminar flow between two concentric circular pipes

9.5.1 Laminar flow between two concentric, rotating circular cylinders

9.6 Flow in Pipes: Dacy s Formula

9.7 The Reynolds Dye Experiment, Laminar/Turbulent Flow in Pipes

9.8 Additional Losses in Pipe Flow

9.9 Summary of 1D pipe flow

9.9.1 Simple pump model

9.9.2 Flow in pipes with non circular cross section.

9.9.3 Examples for one dimensional pipe flow

9.9.4 Network of Pipes

9.10 Free Vortex in a Pool

9.11 Summary and Concluding Remarks

Chapter 10. Fluid Machinery

10.1 Introduction

10.2 Work of a Continuous–Flow Machine

10.3 The Axial Compressor (The Mean Radius Model)

10.3.1 Velocity triangles

10.3.2 Power and compression ratio calculations

10.3.3 Radial variations

10.3.4 Pressure rise limitations

10.3.5 Performance Envelope of Compressors and Pumps

10.3.6 Degree of Reaction.

10.4 The Centrifugal Compressor (or Pump)

10.4.1 Torque, Power, and Pressure Rise

10.4.2 Impeller Geometry

10.4.3 The Diffuser

10.4.4 Concluding Remarks: Axial versus Centrifugal Design

10.5 Axial Turbines

10.5.1 Torque, Power, and Pressure Drop

10.5.2 Axial Turbine Geometry and Velocity Triangles

10.5.3 Turbine Degree of Reaction

10.5.4 Turbochargers (for internal combustion engines)

10.5.5 Remarks on exposed tip rotors (wind turbines and propellers).

10.6 Concluding Remarks

Chapter 11: Elements of Heat Transfer

11.1 Introduction

11.2 Elementary mechanisms of heat transfer

11.2.1 Conductive Heat Transfer

11.2.2 Convective Heat Transfer

11.2.3 Radiation Heat Transfer

11.3 Heat Conduction

11.3.1 Steady One dimensional Heat conduction

11.3.2 Combined heat transfer

11.3.3 Heat conduction in cylinders

11.3.4 Cooling Fins

11.4 Heat transfer by convection

11.4.1 The flat plate model

11.4.2 Formulas for forced external heat conduction

11.4.3 Formulas for forced internal heat convection

11.4.4 Formulas for free (natural) heat conduction

11.5 Heat exchangers

11.6 Concluding remarks

Chapter 12: Automotive Aeroacoustics

12.1 Introduction

12.2. Sound as a Pressure Wave

12.3. Sound Loudness Scale

12.4. The Human Ear Perception

12.5. The One–Dimensional Linear Wave Equation

12. 6. Sound Radiation, Transmission, Reflection, Absorption etc..

12.6.1. Sound Wave Expansion (radiation)

12.6.2 Reflections, Transmission, Absorption

12.6.3Standing Wave (Resonance), Interference and Noise Cancellations

12.7. Vortex Sound

12.8. Example: Sound from a Shear layer

12.9. Buffeting

12.10 Examples on sound sources on a typical automobile

12.11 Sound and Flow Control.

12 .12 Concluding remarks

Appendix

Index