Contents. 1 Introduction to Automobile Aerodynamics 1 Wolf-Heinrich Hucho

Transcription

1 Contents 1 Introduction to Automobile Aerodynamics 1 Wolf-Heinrich Hucho 1.1 Scope Basic Principles Peculiarities of Vehicle Aerodynamics Related Fields History of Vehicle Aerodynamics Survey "Borrowed" Shapes The Eraof the Streamline Parameter Studies One-Volume Bodies The "Bathtub" Body Commercial Vehicles Motorcycles Present and Future Trends State of the Art Detail Optimization Shape Optimization Development Expenditure Aerodynamics and Design Notation 57 2 Some Fundamentals of Fluid Mechanics 59 Dietrich Hummel 2.1 Properties of Incompressible Fluids Density Viscosity Thermal Conductivity Flow Phenomena Related to Vehicles ExternalFlow Internal Flow 62

2 viii Aerodynamics ofroad Vehicles 2.3 Externa! Flow Problems Basic Equations for Inviscid Incompressible Flow Applications Effects ofviscosity Laminar and Turbulent Boundary Layer Development Separation Friction Drag Pressure Drag Overall Forces and Moments Thermal Boundary Layers Special Problems Aerodynamic Noise Body to Body Interference Transport ofsolids Internal Flow Problems Basic Equations for Incompressible Flow Applications Laminar and Turbulent Pipe Flow Curved Pipes Inlets Local Contractions Cross-Section Enlargement Relations Between External and Internal Flow Notation 95 3 Performance of Cars and Light Trucks 99 Hans-Joachim Emmelmann and Wolf-Heinrich Hucho 3.1 Objectives Resistances to Vehiclc Motion Equation of Motion Analysis of Resistances to Motion Aerodynamic Drag Tire Rolling Resistance Ratio of Aerodynamic Drag to Tire Rolling Resistance Climbing Resistance Vehiclc Mass Performance Traction Diagram Maximum Speed Acceleration Time and Elasticity Fuel Consumption, Fuel Economy Dcfinitions Analysis of Fuel Consumption Gear-Ratio Matching Driving Schedules EPA Urban and Highway Cycle Present European Driving Cycle 116

3 Table of Contents ix New European Driving Cycle, and Others Strategy for Lowest Fuel Consumption Fuel Consumption of Light Tracks Outlook Notation Aerodynamic Drag of Passenger Cars 131 Wolf-Heinrich Hucho 4.1 The Passenger Car as a Bluff Body Flow Field Around a Car Analysis of Drag Possible Approaches Physical Mechanisms Local Origins Effect on the Environment Drag and Lift Drag Fractions and Their Local Origins Methodof Observation Front End Windshield and A-Pillar Roof RearEnd Geometry and Flow Separation Boat-Tailing Fastback Notchback Plan View and Side Panels Underbody Wheels and Wheel Housings Front Spoiler Rear Spoiler Attachments Drag from Flow Through a Car Car with Trailer Convoy Driving Strategies for Body Shape Development Objectives Detail Optimization Shape Optimization Facelift Adaptation of Attachments Forecasting Systems and Expert Systems Drag of Passenger Cars in Production Evaluation of Test Results Vehicle Features Vehicle Position, Side Wind Drag Coefficients of Production Cars Research 224

4 x Aerodynamics ofroad Vehicles Objectives Basic Bodies UnconventionalMeasures Concept Vehicles Record Vehicles Notation Directional Stability 239 Alfons Gilhaus and Ralf Hoffmann 5.1 Introduction History of Directional Stability Aerodynamic Forces and Moments Development Aerodynamic Stability Non-Stationary Forces and Moments Aerodynamics and Driving Behavior Lift Force in Straight-Ahead Driving Cornering Power On/Off Reaction Influence of the Aerodynamic Forces on Braking Performance Driving Behavior in Crosswinds Natural Wind and Crosswind Side Wind Reactions Pass-By Maneuvers Driving with Trailer Influence of Vehicle Shape on Aerodynamic Forces and Moments Aerodynamic Properties of the Basic Shapes Lift and Pitching Moment Side Force and Yawing Moment Rolling Moment Comparison ofthe Key Basic Shapes Aerodynamic Effects ofthe Features of Actual Vehicles Cooling Airflow Gaps and Openings Exterior Rearview Mirrors Wheels, Tires, and Underbody RoofLoads Test and Evaluation Methods Wind Tunnel Tests Road Tests Computation of Vehicle Dynamics Driving Simulator Notation 309

5 Table of Contents xi 6 Function, Safety and Comfort 311 Raimund Piatek and Johannes Schmitt 6.1 Differentiated View The Flow Field Around a Vehicle Inlets and Outlets CoolingDucts Air Inlets and Outlets to the Cabin Forces on Bodywork Components Components with Attached Flow Components with Separated Flow Components with Periodic Flow Function of Individual Components External Mirrors Windshield Wipers Sunroofs Convertibles Waterand Dirt Accumulation on Vehicles Safety and Aesthetics Water Flow Dirt Deposits Reducing Splash and Spray Obstruction to Visibility Measuring Impaired Visibility Measures to Rcduce Spray Formation Notation Wind Noise 343 John R. Callister and Albert R. George 7.1 Introduction Mechanisms of Noise Generation and Transmission Source-Path-Receiver Idealized Models of Acoustic Sources Physical Wind Noise Source Types Leak Noise Cavity Noise Wind Rush Noise Airflow Velocity Effect on Wind Noise Levels Design Features A-Pillar Outside Rearview Mirrors Windshield Wipers Radio Antenna RoofRacks Doors 352

6 xii Aerodynamics ofroad Vehicles 13.1 Side Window Systems Fixed Windows HatchRoofs Wind Noise Measurement and Testing Techniques Wind Tunnel versus On-Road Measurements Wind Tunnel Considerations Wind Tunnel Background Noise Simulation of Crosswinds and Gusts in the Wind Tunnel On-Road Measurement Procedures Importance of Narrow Band Spectra for Wind Noise Measurements Overviewof Measurement of Interior Wind Noise Use of Artificial Head Device for Subjective Evaluation Source Identification and Localization Overview of Exterior Wind Noise Measurements Microphone Nose Cones Sound Intensity and Microphone Array Methods Buffeting of Open Windows, Open Sunroofs, and Convertibles Side Windows Sunroofs Convertibles Manufacturing Concerns Process Inspection Leak Detection Using a Smoke Generator Ultrasonic Leak Detector Simple, Quick Inspection Techniques Feedback to the Design Organization Notation High-Performance Vehicles 365 Helmut Flegl and Norbert Singer 8.1 Defmitions Some Historical Milestones The Meaning of Aerodynamics for High-Performance Cars Drag and Lift Handling Driving Tests Angle of Attack and Yawed Airflow Slipstreaming Theoretical Investigations Cooling and Ventilation Design Alternatives Drag and Lift Influence of the Basic Vehicle Configuration Wings Ground Effect Special Body Configurations, Monoposti 397

7 Table of Contents xiii Handling HQQ Cooling and Ventilation 4Q? Special Problems Lap Time and Fuel Economy Near-Sonic Speeds Uncovered Wheels 40g Rotating versus Stationary Wheels of Monoposti Road Version High-Speed Version Effect of Boundary Layer Variation on Wind Tunnel Results Development Methods and Simulation Techniques 411 Trends in Future High-Performance Vehicle Development 413 Notation,,. Commercial Vehicles Hans Götz and Günter Mavr 41^ Target Group 4, <- Tractive Resistance and Fuel Consumption 4lg Drag Reduction and Fuel Consumption 41g Aerodynamic Drag Coefficients of Various Commercial Vehicles Operation in Still Air 40] Drag as a Function of Yawing Angle 42? Wind Influence Definition of Yawing Angle Characterization of Air Resistance in Actual Operating Conditions 424 Reducing Aerodynamic Drag A~>^ Scope for Aerodynamic Changes on Commercial Vehicles Optimization in the Wind Tunnel Problems with Reduced-Scale Models Drag Minimization on Trucks Characteristic Flow and Pressure Conditions Partial Resistance Interference Problem Cab Shape 43] Drag-Reducing Add-On Devices for Trucks Füll Trailer Future Trends in Tractor-Trailer Design Reduction of Aerodynamic Drag on "Truckaway" Units Minimizing Drag of Buses and Delivery Vans Boundary Conditions Characteristic Flow Conditions on Simple Geometrie Bodies Optimization of the Front End Optimization ofthe RearEnd Add-On Devices on the Rear End Future Bus Design Trends 459 Taking Advantage of Aerodynamic Interference Effects Driving in Convoy 46Q Driving Through Tunnels 46i Vehicle Soiling 4fi7

8 xiv Aerodynamics ofroad Vehicles Foreign Soiling Self-Soiling Reductionof Soiling of Bus Sides Reduction of Bus Rear-End Soiling Reduction of Truck Soiling Impingement of Spray on Following Vehicles New Approach to Solution of Spray Mist Reduction The Measuring System Notation Motorcycles 489 Bernward E. Bayer 10.1 One Year Before the Automobile Summary of the Development of Motorcycle Aerodynamics History Today's State-of-the-Art Technology Riding Dynamics and its Relationship with Aerodynamics Performance Specifications Directional Stability C rosswind Behavior Pitch Effects Cornering Methods of Measurement in Road Tests Wind Tunnel Results Measurements on Solo Motorcycles Rider Influences Rider and Pillion Passenger Clothing and Heimets Sidecars Outlook Notation Engine Cooling 533 WulfSebheße, Peter Steinberg, Norbert Deußen, and Dieter Schlenz 11.1 Task of a Cooling System Functional Requirements Requirements to be Satisfied by Passive Characteristics Development Potential of Cooling System Cooling Systems Water Cooling Air Cooling Cooling with Component-Temperature Control Dual-Circuit Cooling System and Warm-Up Concept High-Temperature Cooling 539

9 Table of Contents xv OilCooling Phase-Change Cooling Methods of Computation Principles of Hcat Exchange Heat Transfer and Radiation Hcat Transfer from Combustion Gas to Components Adjacent to Combustion Chamber Heat Transfer from Cylinderto Coolant Heat Transfer at the Engine-Block Wall Heat Conduction in Components Computing Model and Results of Simulation Modular Mcthods for Cooling-System Dimensioning Procedural Concept Coolant Circuit Fan and Fan Clutch Cooling Air System Heat Balance at Engine and Surface of Engine Heat Balance at Radiator Heat Flux Measurement on an Engine Flow Within the Engine Compartment Cooling-Air System Effect of Internal Airflow on Vehicle Aerodynamics Aerodynamics of Internal Flow Air Velocity Distribution in the Radiator Plane Radiator Radiator Fan Tasksofthe Radiator Fan Fan and Drive Design Criteria and Characteristics Volumetrie Flow Power Requirement and Efficiency Noise Generation Mass and Space Requirement Notation Heating, Ventilating, and Air Conditioning of Passenger Cars 577 Holger Großmann 12.1 Definition of Objectives: Comfort and Safety Climate Physiology Parameters Affecting the Occupants Interior Temperaturc Temperature Stratification Air Speed Inhomogeneous Airflow Humidity Solar Radiation Comfort Model Devised by P.O. Fanger 582

10 xvi Aerodynamics ofroad Vehicles Climate Measuring Dummies Heart Rates Parameters Affecting the Climate Inside a Car Airflow Through the Passenger Compartment Intake and Outlet Vents Airflow Definition Airflow Measuring Methods Characteristic Curves Fan Characteristics Leakage Characteristics L w Outlet Characteristics A w Ventilation Characteristics B w Ventilation Airflow Ventilation Airflow with Slide-Tilt Sunroof Open Incoming Leakage Airflow Significance of Incoming Leakage Airflow Determination of Incoming Leakage Airflow Examples Heat Flow Through the Passenger Compartment Heat Transfer Through the Body Interface Heater Core/Passenger Compartment Characteristics of the Heater Core Steady Interior Temperature in Fresh-Air Mode Unsteady Interior Temperature in Fresh-Air Mode Mean Interior Temperature in Recirculating Mode Engine with Low Fuel Consumption Interface Evaporator/Passenger Compartment Characteristics of Evaporator Mean Interior Temperature in Fresh-Air Mode Mean Interior Temperature in Recirculating Mode Interface Evaporator/Refrigeration Cycle Unsteady Cooling in Recirculating Mode Solar Radiation Solar Radiation Through the Windows Heating Up a Parked Car Solar-Cell Operated Independent Ventilation Heating Up While Vehicle in Motion Flow of Water Vapor and Dust Water Vapor Gas Concentration in the Passenger Compartment Defrosting and Defogging of Windows Filtering Control Systems Temperature Control of a Heating System Automatic Control of Evaporators Automatic Control of Air Distribution and Temperature Heater and A/C Units in Production Air-Side Controlled Heater 622

11 Table of Contents xvii Water-Side Controlled Heater Integrated AC Systems Notation Wind Tunnels 627 Wolf Heinrich Hucho 13.1 Scope Requirements fora Vehicle Wind Tunnel Simulation of the Various Aspects of On-Road Driving Some Fundamentals of Wind Tunnel Technique Selection of References Configuration Considerations Properties of the Essential Components Planning a Test Test Section Nozzle Determination of Wind Speed Plenum Heat Exchanger and Sun Load Equipment Limitations of Simulation Systematic Errors Representation of the Road Wind Tunnel Corrections Objectives ClosedTest Section Open Test Section Boundary Layer Effects Yawed Model Thermal Tests Tests with Reduced-Scale Models Advantages and Disadvantages Details of Model Construction and Test Technique Reynolds Number Effects Existing Automobile Wind Tunnels Classification of Test Facilities Full-Scale Wind Tunnels Wind Tunnels for Reduced-Scale Models Climatic Tunnels Dynamometers with Fan Comparative Measurements Final Comments and Future Prospects Notation 714

12 xviii Aerodynamics ofroad Vehicles 14 Measurement and Test Techniques 717 Görgün A. Necati and Wigberl R. Kohl 14.1 Scope Measuring Equipment and Transducers Measurement of Aerodynamic Forces and Moments Wind Tunnel Balances Resolution of Aerodynamic Forces and Moments into Their Components Measurement of the Projected Frontal Area Pressure Measurements Pressure Probes Pressure Transducers Measurement of the Airflow Velocity Determination of the Airflow Velocity Outside and Inside a Vehicle Determination of the Test Speed in a Wind Tunnel Measurement of Flow Direction Temperature Measurement Temperature Sensors Typical Temperature Measurement Errors Test Data Collection and Data Management Wind Tunnel Testing Methods Measurement of the Aerodynamic Coefficients Airflow Management Tests Measurement of the Airflow Rate Through the Passenger Compartment Airflow Rate Measurement by Means of Extraction Curves Alternative Methods of Measuring Airflow Rate Through the Passenger Compartment Passenger-Compartment Heating and Air Conditioning Tests Defrosting and Demisting Tests Engine Cooling Tests in a Wind Tunnel Flow Visualization Techniques Wind-Noise Measurement in a Wind Tunnel Water Basin versus Wind Tunnel Road Testing Methods Measurement of the Aerodynamic Drag Force in a Coast-Down Test Crosswind Tests Engine Cooling Road Tests Soil Deposits on Glass Surfaces and Vehicle Body Areas Wind Noise Measurement on the Road Notation Computational Fluid Dynamics 765 Syed R. Ahmed 15.1 Introduction Some Salient Features of Road Vehicle Flow 767

13 Table of Contents xix 15.3 Demands on a CFD Simulation CFD Methods for Vehicle Aerodynamics General Remarks Approximations of the Navier-Stokes Equations Basic Stepsofa CFD Computation Three-Dimensional Grid Generation Linear CFD Methods The Panel Method Some Applications of the Panel Method Nonlinear CFD Methods Solution Schemes for Nonlinear Methods Euler Methods Methods Based on Time-Averaged NS Equations Turbulence Modeling Eddy Viscosity Concept Turbulence Models Algebraic Models Transport Equation Models Non-Eddy Viscosity Concept Turbulence Models Some Applications ofrans Methods Methods Based on Unsteady NS Equations Large Eddy Simulation (LES) Direct Numerical Simulation (DNS) Some Applications of DNS Methods Zonal Methods Future Computer Requirements and Trends of Supercomputer Development Evaluation and Perspective of CFD Methods Notation 835 References 837 Author Index 875 Subject Index 883 Abbreviations 913 About the Authors 915