|Politecnico di Torino|
|Academic Year 2014/15|
Car body design and aerodynamics
Master of science-level of the Bologna process in Automotive Engineering - Torino
This module provides information regarding the design of the vehicle bodywork keeping in mind the various functions involved. The areas covered include ergonomics, climatic, acoustical and vibrational comfort, layout of the structure and passive safety.
It provides the concepts of aerodynamic behaviour in motor vehicles and its methods of analysis and numerical and experimental optimisation, in harmony with style, architectural needs as well as the cooling systems are also dealt with.
Expected learning outcomes
Students should acquire skills in the area of postural ergonomics, bodywork architecture, noise and vibration, passive safety and crash protection.
Metodology of vehicle aerodynamics, experimental techniques in wind tunnel and CFD (Computational Fluid-Dynamics) instruments of calculation used for the motor vehicle.
Prerequisites / Assumed knowledge
Vehicle dynamics, structural analysis, mechanical vibrations, fluid mechanics and the numeric calculus methods.
1 - Introduction
Prerequistes and functions of the motor vehicle from the bodywork point of view.
2 – Ergonomics and use of space
Principles of posture
Principles of human vision
Percentiles and manikins for packaging
Main constraint to interior packaging coming from vehicle body structure: wheel arches, tunnel, firewall, pedals, underbody.
Seating position and seat comfort
External and Internal visibility
Manoeuvrability and command access.
4 – Structural integrity
Bodywork design: construction details for hatchbacks and saloons, spiders, MPVs, commercial vehicles, lorry cabs.
Reference load cases for design: loads coming from vehicle manoeuvres and obstacles, internal loads due to powertrain, suspensions and safety belts; loads on bodywork surface.
Simplified model for the functional analysis of the car structure when subject to internal and external loads.
Introduction to the analysis of thin walled structures.
Structural surface method to analyse torsional and flexural behaviour of open and closed chassis architectures.
Structural analysis of monocoque configuration: underbody types and evaluation of their torsional stiffness. H, I, X, ladder frame analysis. Influence of open or closed cross section beams.
5 – Acoustical and vibrational behaviour
Principles of the physiology of the human ear and noise quality
Vibration and noise sources
Dynamic behaviour of the bodywork and modal analysis
Noise diffusion via air
6 - Safety
Preventative, active and passive safety
Main injury criteria, HIC, tibia index, neck, viscous criteria.
Role of restraint system and main parameters affecting the occupants accelerations during a crash.
Passive safety: reference to international standards
Crashes of small intensity: Insurance tests, tests on bumpers.
High speed crash tests for homologation and rating.
Prerequisites and evaluation of devices.
1. Reference to fluid-dynamics
Equations of movement for uncompressible and compressible fluids.
Limited laminar and turbulent layers
Concepts of resistance from friction and pressure.
Criteria for similarities
2. Aerodynamic resistance
Resistance to movement.
Effect on consumption and performance.
Flow structure around squat bodies
Contributions to the aerodynamic resistance and parameters of synthesis.
Influence on the aerodynamic performance of significant variations of shape.
Resistance in commercial and industrial vehicles.
3. Aerodynamic problems inherent to the dynamic behaviour, to the comfort and to the cooling
Stability with lateral wind.
Lift decrease for high performance vehicles.
Aerodynamic forces on the bodywork.
Soiling and dispersion of exhaust fumes.
4. Experimental aerodynamics
Automobile wind tunnels.
Tests on scale models.
Measurement of the strength and aerodynamic torque.
Techniqu es for measuring the fluid-dynamic size (pressure, speed, heat cables, LDV, PIV).
Analysis of aerodynamic noise.
Analysis of air flows under the bonnet
5. Computational aerodynamics
Numeric methods for equations of fluid motion.
Calculations grids and their creations based on CAD geometry.
Examples of turbulence.
Elaborations and visualization of the results.
6. Aerodynamic development of vehicles
Simultaneous development of aerodynamic forms, style and planning of the vehicle.
Improvement of the form and interaction with the style.
Varying evaluations of the shaft and lateral winds.
Optimization of the additions.
Reduction of the bodywork resistance.
Students carry out practical work on the following:
Ergonomical evaluation of a vehicle; postural comfort; external visibility
Evaluation of the torsional stiffness of a bodywork via a simplified model and identification of the possible improvements.
Applicable examples of the calculus codes CFD.
Instrumentation of measure for calibration.
Measuring of pressure field on scale models.
Texts, readings, handouts and other learning resources
Folders of notes are available for the students.
Texts for further information :
L. Morello, L. Rosti Rossini, G. Pia, A. Tonoli, "The Automotive Body", Voll, I and II, Springer, 2011.
J. Fenton, "Handbook of Vehicle Design Analysis", SAE, 1999 .
W. Karwowsky, "Automotive Ergonomics", Taylor & Francis, 1993 .
J. Happian-Smith e altri, "An Introduction to Modern Vehicle Design", SAE, 2002 .
T. Gillespie, "Fundamentals of Vehicle Dynamics", SAE, 1999.
Hucho W. H. – Aerodynamics of Road Vehicles.
Pope-Rae – Low Speed Wind Tunnel Testing
Assessment and grading criteria
There is a written test at the end of the didactic period, a further wirtten examination at the end of the module and assessment of practical work completed during the course.
Programma definitivo per l'A.A.2014/15