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Developments in wind tunnel testing of road vehicles
Published April 14, 1997 by Royal Aeronautical Society in United Kingdom
Wind tunnels have been used for at least seventy years for investigating the aerodynamic characteristics of road vehicles. This use has intensified markedly, however, since the oil crisis of 1973-4. Full-scale automotive wind tunnels have proliferated, and small-scale testing has also increased.
Various wind-tunnel designs have been adopted, with open-jet, closed-jet and slotted-wall test sections and open and closed-return circuits. Representation of the road surface by the been employed to improve this representation by minimizing the tunnel-floor boundary layer effects, and new variations are currently under development.
Steady cross-wind conditions are usually simulated by setting the vehicle/model at one or more yaw angles relative to the tunnel airstream. Additionally, some novel techniques have recently been developed for simulating cross-wind gusts.
A wide range of test activities is performed in automotive wind tunnels. Most commonly, aerodynamic forces and pressures are measured. Flow visualization and velocity surveys are also frequently performed, for various purposes.
Climatic testing of vehicles is a further major activity in automotive wind tunnels, with the twin aims of ensuring adequate cooling of various mechanical components and providing acceptable passenger comfort in all likely operating conditions. Passenger comfort is also the objective behind the growing use and development of aero-acoustic wind tunnels.