Automotive Wind Tunnels - Making Aerodynamic Cars
This delay was also caused by the fact that automotive aerodynamics differs from aircraft aerodynamics in many ways. For example, the shape of a road vehicle is much less streamlined compared to an aircraft. Then, the vehicle does not run in free air and its motion is less affected by aerodynamic forces, while operating speeds are much lower.
It first started as a way to determine ways to reduce the power required to move the vehicle on roadways at a given speed. As early as the 1920s engineers began to consider automobile shape in reducing aerodynamic drag at higher speeds.
By the 1950s, German and British automotive engineers were systematically analyzing the effects of automotive drag for the higher performance vehicles. By the late 1960s, scientists also became aware of the significant increase in sound levels emitted by automobiles at high speed. These effects were understood to increase the intensity of sound levels for adjacent land uses at a non-linear rate.
Soon highway engineers began to design roadways to consider the speed effects of aerodynamic drag produced sound levels, and automobile manufacturers considered the same factors in vehicle design. Today, the majority of automakers have their own wind tunnel testing facilities, using it in studying and developing the aerodynamic features of any new vehicle. The main concerns of automotive aerodynamic are reducing drag, reducing wind noise, minimizing noise emission and eliminate as much as possible any instability occurring at high speeds.
A wind tunnel typically comprises a test section where a model or vehicle can be mounted and viewed whilst air is either blown or more usually sucked over it by a fan or number of fans. Data can usually be gathered from a balance on which the model or
Wind tunnels enable the following data to be acquired: aerodynamic forces; drag, lift, side force and moments; pitch, yaw, roll; variation of aerodynamic forces and moments with yaw; surface pressure distribution; the influence of different vehicle details on the above; vehicle cooling drag; assessment of brake cooling flows; aero-acoustic data; affect of aerodynamic features and aids.
Aerodynamics expertise is frequently called upon for a diverse selection of non-automotive products. From other forms of transport such as trains and bicycles through to totally unrelated products... Lifeboats, aerials, wheely bins, tents, sports clothing and even world class skiers.
Model Scale Testing
Full Scale Testing
It wasn’t until 1960 that the first dedicated automotive wind tunnel was inaugurated by the specialists at MIRA, opening its doors for vehicle aerodynamics research. Since then, MIRA's aerodynamicists have been investigating the use of computers to predict the aerodynamic performance of different vehicle shapes initially with in-house developed empirically based codes.
As the power of computers and software increased MIRA's engineers have been able to use Computational Fluid Dynamics (CFD) to evaluate vehicle design and styling before physical models or prototypes are available.
GM specialists say the aerodynamic work typically begins in 1/3-scale clay models to test the overall shape of a vehicle, going through a series of stages until moving to full-scale development, often testing aerodynamic changes as small as one millimeter.
The Most Advanced
There are two wind tunnels, both with a running belt simulating the road related speed as well as the air speed. The largest one, designed for full-scale model and actual car (as well as other sort of vehicles or test) can test aerodynamic behaviors at speeds up to 300 km/h. The second one, called Aerolab because it is dedicated to advanced aerodynamic research rather than just tests, is large enough to allow test of full size models and cars but is specially equipped for scale models. With the air velocity reaching 140 km/h they simulate condition of vehicles driving up to 280 km/h with 1:2 scale models.