SAE R-392-2014 Theory and Applications of Aerodynamics for Ground Vehicles (To Purchase Call 1-800-854-7179 USA Canada or 303-397-7956 Worldwide).pdf

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1、 Theory and Applications of Aerodynamics for Ground Vehicles 392_book.indb 1 2/18/14 10:17 AMOther SAE books of interest: Aerodynamics of Road Vehicles, Fourth Edition By Wolf-Heinrich Hucho (Product Code: R-177) Fundamentals of Vehicle Dynamics By Thomas D. Gillespie (Product Code: R-114) Race Car

2、Vehicle Dynamics By William F. Milliken and Douglas L. Milliken (Product Code: R-146) For more information or to order a book, contact SAE International at 400 Commonwealth Drive, Warrendale, PA 15096-0001, USA; phone 877-606-7323 (U.S. and Canada only) or 724-776-4970 (outside U.S. and Canada); fax

3、 724-776-0790; email CustomerServicesae.org; website http:/ /books.sae.org. 392_book.indb 2 2/18/14 10:17 AM Theory and Applications of Aerodynamics for Ground Vehicles By T. Yomi Obidi Warrendale, Pennsylvania USA 392_book.indb 3 2/18/14 10:17 AM400 Commonwealth Drive Warrendale, PA 15096-0001 USA

4、E-mail: CustomerServicesae.org Phone: 877-606-7323 (inside USA and Canada) 724-776-4970 (outside USA) Fax: 724-776-0790 Copyright 2014 SAE International. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, distributed, or transmitted, in any form or by a

5、ny means without the prior written permission of SAE International. For permission and licensing requests, contact SAE Permissions, 400 Commonwealth Drive, Warrendale, PA 15096-0001 USA; email: copyrightsae.org; phone: 724-772-4028; fax: 724-772-9765. ISBN 978-0-7680-2111-0 SAE Order Number R-392 DO

6、I 10.4271/ R-392 Library of Congress Cataloging-in-Publication Data Obidi, T. Yomi, 1955-Theory and applications of aerodynamics for ground vehicles / by T. Yomi Obidi.pages cmIncludes bibliographical references and index.ISBN 978-0-7680-2111-01. Automobiles-Aerodynamics. 2. Trucks-Aerodynamics. I.

7、Title. TL245.O25 2014629.231-dc232013044452 Information contained in this work has been obtained by SAE International from sources believed to be reliable. However, neither SAE International nor its authors guarantee the accuracy or completeness of any information published herein and neither SAE In

8、ternational nor its authors shall be responsible for any errors, omissions, or damages arising out of use of this information. This work is published with the understanding that SAE International and its authors are supplying information, but are not attempting to render engineering or other profess

9、ional services. If such services are required, the assis- tance of an appropriate professional should be sought. To purchase bulk quantities, please contact: SAE Customer Service Email: CustomerServicesae.org Phone: 877-606-7323 (inside USA and Canada) 724-776-4970 (outside USA) Fax: 724-776-0790 Vi

10、sit the SAE International Bookstore at BOOKS.SAE.ORG Cover photo courtesy of Jaguar Land Rover/Exa Corporation. Used with permission. 392_book.indb 4 2/18/14 10:17 AMDedication To nayin-yi Oshomoshi Olodumare 392_book.indb 5 2/18/14 10:17 AM392_book.indb 6 2/18/14 10:17 AMvii Contents Preface .xiii

11、Acknowledgments xv Introduction . xvii Chapter 1 Drag.1 1.1 General Concept of Drag. 1 1.2 High Reynolds Number Flow versus Low Reynolds Number Flow 5 1.3 General Airfoil Flow Behavior 6 1.4 Airfoil Geometry. 10 1.5 Flow Classification and Continuity: Steady and Unsteady Flow, Streamline . 10 1.6 Bo

12、undary Layer . 17 1.7 Airfoil Theory . 22 1.8 Lift, Drag, Side Force, and Moment. 26 1.9 Sources of Drag in Ground Vehicles 30 Key Terms 31 Review Questions 32 Important Questions/Application Questions 32 Exercises 32 Projects . 33References 33 Chapter 2 Noise and Vehicle Soiling 35 2.1 Sources of N

13、oise . 38 2.2 Types of Aerodynamic Noise 42 2.3 Locating Noise Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45 2.4 Noise Measurement 46 2.5 Material-Based Noise Abatement. 47 2.6 Design-Based Noise Abatement 48 2.7 Wind Tunnel Noise. 50 2.8 Vehicle Soilin

14、g . 51 Key Terms 60 Review Questions 60 Application Question. 60 Exercises 60 Projects . 61 392_book.indb 7 2/18/14 10:17 AMviii ContentsReferences 61 Chapter 3 Experimental Aerodynamics for Ground Vehicles 63 3.1 Wind Tunnel 63 3.2 Track and Road Testing . 88 Key Terms 91 Review Questions 92 Applic

15、ation Questions 92 Exercise. 92 Project 93References 93 Chapter 4 Computational Aerodynamics for Ground Vehicles 97 4.1 Making a Case for Computational Fluid Dynamics CFD. 97 4.2 Modeling . 98 4.3 Methods of Modeling. 99 4.4 Meshing . 100 4.5 Boundary Conditions 101 4.6 Solution Methods . 104 4.7 In

16、terpretation of Results . 107 4.8 CFD Packages 108 4.9 Turbulence Modeling 109 Key Terms . 110 Review Questions. 110 Application Question 110 Exercise 110 Project . 111References . 111 Chapter 5 Vehicle Stability and Performance .113 5.1 Traction 114 5.2 Power Requirement . 120 5.3 Tire Contribution

17、 . 121 5.4 Sideslip and Turning 125 5.5 Trailing Vortices 127 5.6 Control Surfaces 128 5.7 Car Underbody Flow 128 5.8 Cross Wind. 130 5.9 Truck-Car Passing Interaction. 131 5.10 Effect of the Environment on Aerodynamic Drag 133 5.11 Effect of Aerodynamic Drag on Fuel Consumption 133 392_book.indb 8

18、2/18/14 10:17 AMix Contents Key Terms . 134 Review Questions. 135 Application Questions . 135 Exercises. 135 Project . 136References . 136 Chapter 6 Vehicle Sectional Design 139 6.1 Car Front and Mid Sections. 141 6.2 Car Rear Section 146 6.3 Downforce Devices 148 6.4 Underside 148 6.5 Vehicle Heigh

19、t 150 Key Terms . 152 Review Questions. 152 Projects 153References . 153 Chapter 7 Trucks, Trailers, and Buses. 155 7.1 Light Trucks, Minivans, and Sport Utility Vehicles (SUVs) . 156 7.2 Medium Trucks . 159 7.3 Large Trucks and Buses 159 7.4 Side Skirts . 165 7.5 Truck-Car InteractionA Further Trea

20、tment 166 7.6 Applications of Computational Aerodynamics to Large Ground Vehicles 169 Key Terms . 170 Review Questions. 170 Application Questions . 170 Exercises. 170 Projects 171References . 171 Chapter 8 Railroad Train Aerodynamics 173 8.1 Low-Speed Passenger Train 174 8.2 High-Speed Passenger Tra

21、in 175 8.3 Vibration in High-Speed Trains . 177 8.4 Freight Train . 179 8.5 Aerodynamic Considerations in Engine Module Design 179 8.6 Aerodynamic Considerations in Train Car Design . 181 Key Terms . 182 Review Questions. 182 392_book.indb 9 2/18/14 10:17 AMx Contents Application Questions . 183 Exe

22、rcises. 183 Projects 183References . 184 Chapter 9 Severe Service and Off-Road Vehicles 185 9.1 Construction Trucks . 186 9.2 Garbage Collection Trucks . 187 9.3 Farm Machinery 188 9.4 In-Plant Carts. 188 9.5 Sections of Severe Service and Off-Road Vehicles 189 9.6 Sectional Aerodynamic Design 189 9

23、.7 Underbody Design 189 9.8 Soiling in Severe Service Vehicles 190 Key Terms . 191 Review Questions. 191 Application Question 192 Exercises. 192 Projects 192References . 192 Chapter 10 Race Cars, Sports Cars, and Convertibles . 193 10.1 Race Cars and Sports Cars 194 10.2 Rally Cars and Dragsters. 19

24、9 10.3 Convertibles 199 Key Terms . 202 Review Questions. 202 Application Questions . 203 Exercises. 203 Project . 203References . 204 Chapter 11 Motorcycles.205 11.1 Motorcycle Classifications 206 11.2 Design for Aerodynamics 208 11.3 Motorcycle Stability and Control 209 11.4 Soiling in Motorcycles

25、 . 211 11.5 Noise Generation and Effect 212 11.6 Aerodynamic Effects of the Track and the Pack 215 11.7 Motorcycle-Truck Interaction at High Speed 215 11.8 Motorcycle Engine Cooling. 216 11.9 Three-Wheeled Motorcycle . 217 Key Terms . 218 392_book.indb 10 2/18/14 10:17 AMxi Contents Review Questions

26、. 218 Application Questions . 219 Exercises. 219 Project . 219References . 219 Chapter 12 Internal Aerodynamics and Cooling System . 221 12.1 Underhood Initiated Underbody Flow . 222 12.2 Internal Air Flow 224 12.3 Radiator Air Flow . 233 12.4 Thermal Effect 240 12.5 Cabin Air Conditioning 240 Key T

27、erms . 243 Review Questions. 243 Application Questions . 244 Exercise 244 Projects 244References . 245 Chapter 13 Concept Ground Vehicles.247 13.1 Passenger Car 248 13.2 Race Car . 249 13.3 Trucks and Trailers 251 13.4 Motorcycles 251 13.5 Train 252 13.6 Severe Service and Off-Road Vehicles 252 13.7

28、 Aerocars and Amphibians 253Reference 253 Nomenclature255 Conversion Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 Index 259 About the Author 267 392_book.indb 11 2/18/14 10:17 AM392_book.indb 12 2/18/14 10:17 AMxiii Preface The focus of this book is on cars

29、 and trucks, these being the most common ground vehicles in the speed range in which the study of ground vehicle aero- dynamics is beneficial. With an understanding of ground vehicle aerodynamics, one is equipped with a basis for the design of vehicles with better fuel efficiency, with improved vehi

30、cle performance, and with increased passenger comfort. Naturally, many of the materials presented herein can be found in other books on ground vehicle aerodynamics or even in aerodynamic books in general. There are, however, some topics that are either skipped or treated rather lightly, the same top

31、ics that I consider deserving of a more rigorous treatment than has been found in the few books that address them. One such topic is car-truck interaction, when one vehicle (usually the smaller one) is overtaking the other. There is a direct and instant benefit in terms of safety on the highway from

32、 understanding the forces at play when one vehicle passes the other in the same direction and sense. Also, most of the books on ground vehicle aerodynamics appear to target the practicing engineer or aerodynamicist, leaving aspiring students wondering more than implementing at the time that they are

33、 still in school. This book aims to introduce the student to ground vehicle aerodynamics and to methodically guide the student through the school days to the practicing level, at which stage there are a wider range of books to consult. The material in this book has been previously presented, in part

34、, at seminars and in professional development sessions. T.Y.O. 392_book.indb 13 2/18/14 10:17 AM392_book.indb 14 2/18/14 10:17 AMxv Acknowledgments The works of pioneers often appear to be of little significance at the time that the work is done. The works of pioneers are often pieces, formed from t

35、houghts, looking for other pieces to form a body of thought, if complimentary, or a worthy provocateur, if different, yet challenging. Together they form the foun- dation for a discipline. This book has enjoyed the benefits of the foundation laid by the pioneers of aerodynamics in general, and of th

36、e aerodynamics of ground vehicles in particular. Some of those pioneers are well known, while others are unsung, and unpublished, yet valuable. It is my hope that this book bears testimony to the diligence of the forerunners in the field of ground vehicle aerodynamics, and that it provides some ligh

37、t for those yet to come, as well as for others in the field. I am profusely thankful to John Fischer, who volunteered both time and resources to facilitate the completion of this book. I am very thankful to Martha Swiss of SAE International (SAE) for her unusual patience through what almost became a

38、 perpetual shift of manuscript due dates. Thanks to Heather Slater and to Bill Schall, both of SAE, for critically reviewing the manuscript and ensuring proper drawing format, respectively. My dry days were lightened with prayers, encouragement, and assistance from family and friendsPapa, Mama, Funl

39、ola, Shola, Tosin, Teresa, “the kids” (from Tunmishe through Onoye), Uncle Dele, Aunty Marcy, Aunty Glendora, Uncle Bill (Babake), Dr. Joshua Owoeye, Aunty Margaret Omodara, Chief Adesola Awolola, and many more. May heaven smile upon you in your times of need. T.Y.O. 392_book.indb 15 2/18/14 10:17 A

40、M392_book.indb 16 2/18/14 10:17 AMxvii Introduction The necessity for improved vehicle fuel economy is a major motivator in the attempt to better understand ground vehicle aerodynamics. Drag, lift, and sta- bility are three concepts that constitute the cornerstone in the study of ground vehicle aero

41、dynamics. The consideration of stability typically influences the design of control surfaces, a common feature in race cars. Though lift is a desir- able occurrence in flight, groundedness, an inverse of lift, is the goal in ground vehicle design. This negative lift is often referred to as downforce

42、 in ground vehicle aerodynamics. Perhaps the single largest aerodynamic consideration in the design of ground vehicles is drag. A major goal of the effort to better understand ground vehicle aerodynamics is the optimum reduction of aerodynamic drag. The benefits of a successful drag reduction are in

43、stant. They include better fuel efficiency, improved vehicle performance, and increased passenger comfort. What really is drag? To answer this question, perhaps we should first treat the question, What really is aerodynamics? , and, by extension, address the concept of ground vehicle aerodynamics. A

44、erodynamics is simply the study of the forces involved in the movement of an object through the air. Various objectsair- planes, cars, trains, footballs, cricket balls, tennis balls, baseballs, feathers, even agbada (Fig. 1.1)interact with and are therefore affected by the dynamics of the surroundin

45、g air. Because of the general implication of the term vehicle, vehicle aerodynamics narrows our consideration to transportation. Ground vehicle narrows it even further to vehicles that make contact with the ground through- out their movement. So ground vehicle aerodynamics is the aerodynamic study o

46、f cars, trains, trucks, trailers, motorcycles, carts, bicycles, and, lest we forget, human beingswalking, running, or crawling. Air molecules bombard everything that they encounter and flow against or past it. When the air molecules are not constrained, the flow is generally termed incompressible, a

47、nd when this incompressible flow travels past a cooperative object such as an airfoil, we have a streamline of the flow. Streamlines are typi- cally laminar flow. As flow speed increases rapidly or as obstruction to flow increases in the form of friction or in the form of a blunt obstacle, the tende

48、ncy for turbulence increases. The streamlines soon give way to micro flow reversals and the build-up of the shear layer at the incipience of turbulence. Be it laminar or turbulent flow, drag is generated as a reaction to flow, and all objects struggle to overcome this drag, which is either in the fo

49、rm of pressure or friction. The pressure form of drag is dominant in flow against blunt objects such as a flat plate or a bluff body positioned head-on against the flow. Drag in the form of friction is the most common form of drag experienced by moving bodies, the latter having evolved to minimize pressure drag. 392_book.indb 17 2/18/14 10:17 AMxviii Introduction Although the airfoil is considered the most efficient form of design for drag reduction, ironically, protrusions from an almost-airfoil design actually assist in reducing the drag on the body, especially at high speed.