From a light breeze to a hurricane
As a general rule: whatever the route profile, the vehicle and its components are always tested under real-life conditions with a flow of air around them. This is provided in both test facilities by a powerful wind tunnel. Its turbine can produce any form of airflow required, from a light breeze to a hurricane. As an extreme example, snowstorms with hurricane-force winds of up to 200 km/h would also be possible. Even at wind speeds of over 100 km/h, a human being cannot stand without something to hold on to.
Of course the wind speed can also be regulated as required. The airflow is controlled via a speed-regulated fan as well as by air jets with an adjustable airflow cross-section. As a rule of thumb: the smaller the cross-sectional area
of the jet, the higher the speeds that can be achieved. For tests with passenger cars, the usual cross-section is eight square metres; for larger vehicles such as the Sprinter, it is increased to twelve square metres. For the Mercedes-Benz SLS AMG and other sports cars, on the other hand, the test engineers will choose a smaller opening, with an airflow cross-section of seven square metres.
As well as by adjustment of the wind speed, the sensitive regulation of climatic conditions is made possible by the ability to set the relative humidity in both the cold and the hot tunnel to a level between 5 and 95 percent. The two climatic wind tunnels do however differ in their further details, in order to be able to fulfil the wide-ranging requirements of the engineers.