Shell Eco-marathon GDP 2013

Rules and Regulations Aerodynamic Design

Alexandros Ioannou

Outline• Rules and Regulations– Importance– Enforcement– Key Rules

• Aerodynamics– Different forms of drag– Mach and Reynolds number– Optimisation of the top profile– Ground clearance– Wheel fairings– Future Work

Rules and Regulations

Introduction

• In all sports Rules and regulations are important especially in motor racing

Importance

• Influence the design of the car due to restrictions

• Must comply in order to participate in practice or attempts

Enforcement

• Can be found online• Created Excel with relevant rules under each

role for easy access• Booklet containing rules ready to hand• Periodic checks

Dimensions

• Height Track ratio max 1.25 • Track width: at least 500 mm• Wheelbase: at least 1000 mm.

Chassis Height

• Height Track width ratio: maximum 1.25 • Required lowering of floor by 113mm• Used uprights

Conclusion

• There will be tests at the event to verify the legality of the car

Aerodynamic Design

Introduction

• Aerodynamic drag accounts for around half of the total drag

• Area for most improvement• Minimise drag and neutral lift

Drag

• Two main sources:1.Skin

2.Pressure

Theoretical estimation

• Velocity 6.9 m/s• Mach number: 0.020- incompressible• Reynolds number 1.26 million based on 2.70m

length – turbulent (3000~5000)

Initial Design

• For top section symmetrical aerofoil, tear drop shaped, delay transition

• For side, truncated half tear drop shape• Initial estimation of drag coefficient 0.16

Optimisation of top section

• Used XFR5.• Validation: Tested numerous NACA aerofoils.

Results with 15% at 0 CL of experimental from ‘Theory of Sections’ at same Reynolds number

Optimisation of top section• Inputted chassis into software. • Iterative process. Used spline to create best

aerofoil that fit our chassisVersion Sectional CD

1 0.00714

2 0.00724

3 0.00811

Ground clearance

• For a length of 2.70m minimum ground clearance is 10.0cm. Final Design has 11.5cm

Wheel fairings

• Decrease tyre drag by around 50%• Same NACA 66-021 aerofoil for all fairings• What changed was length

Wheel fairings

• Final wheel fairings length

Future work

• Optimise top and side section using CFD and wind tunnel

• Optimise wheel fairing junctions. Minimise interference drag

• Investigate performance in side winds• Wheel discs instead of spokes• Optimise camber for zero lift

Summary

• Rules and Regulations– Importance– Enforcement– Key Rules

• Aerodynamics– Different forms of drag– Mach and Reynolds number– Optimisation of the top profile– Ground clearance– Wheel fairings– Future Work

References• Joseph Katz (2006). Race Car Aerodynamics: Design for

Speed. Cambridge: Bentley Publisher. P52.• Buchheim, R., Deutenbach, K.-R., Luckoff, H.-J. (1981).

Necessity and Premises for reducing the aerodynamic drag of future passenger cars.SAE paper 810 185, Detroit.

• R H Barnard (2009). Road Vehicle Aerodynamic Design: an Introduction. 3rd ed. Hertfordshire: MechAero Publishing. P35.

• Wolf-Heinrich Hucho (1987). Aerodynamics of Road Vehicles. London: Betterworth & Co. P129, 232.

• John D. Anderson, JR (2011). fundamentals of Aerodynamics. 5th ed. New York: McGraw Hill. P381.