On-road Aerodynamic Measurement Techniques
2022-01-1096
03/29/2022
- Event
- Content
- The development of car shape to provide optimal aerodynamic behaviour is typically an iterative process involving test and development. Two main test and development methods are used: wind tunnel testing (of both models and full-size cars) and Computational Fluid Dynamic (CFD) modelling. However, especially for development teams working on a small budget, there are problems with both approaches. Wind tunnel testing of full-size cars is extremely expensive. In addition, access may be problematic, especially for longer periods of testing. To be accurate, wind tunnel testing of models requires a high degree of model fidelity and appropriate wind tunnel conditions to avoid adverse Reynolds Number effects. CFD modelling, while very valuable, varies widely in quality and is always proved through physical testing. Another approach, covered in this paper, is to carry out aerodynamic testing on the road. For example, car aerodynamic drag is normally reduced if areas of separated flow along the length of the body are minimized. Areas of separated flow can be accurately identified through on-road tuft testing, including in real-world yaw conditions and with high turbulence caused by roadside structures. Aerodynamic pressures acting on bodywork panels are responsible for most of the drag and lift forces affecting cars. For example, increasing the aerodynamic pressures acting on the car’s base (the area exposed to the wake) will typically reduce drag. Increasing the pressures acting on the upper surface panels will typically reduce aerodynamic lift. On-road aerodynamic testing can be used to directly measure these pressures, and any change in pressures resulting from body changes. Aerodynamic lift or downforce directly affects tyre grip and the magnitude of induced drag. Lift / downforce can be directly measured in on-road testing. Especially in locations where weather conditions are favorable for most of the year, on-road aerodynamic testing can be carried out quickly, very cheaply and with sufficient accuracy to make the testing worthwhile.
- Citation
- Edgar, J., "On-road Aerodynamic Measurement Techniques," SAE Technical Paper 2022-01-1096, 2022, .