The new Mercedes-Benz E-Class Cabriolet - TecDay Aerodynamic 2009 - PART XI


Stuttgart, Germany, Dec 15, 2009

Glossary: Terms and innovations from A to Z

: this science deals with all processes that occur when air flows around and through a vehicle.

AIRCAP®: this automatic draught-stop can be activated at the push of a button in order to reduce interior turbulence significantly in the new Mercedes-Benz E-Class Cabriolet. AIRCAP® consists of two components: a wind deflector that can be extended by six centimetres with a net in the roof frame and a draught-stop between the rear seats.(Optional)

AIRSCARF®: this unique neck-level heating system is integrated into the backrests of the front seats and blows warm air out of outlets in the head restraints. In the new E-Class Cabriolet, the outlet nozzle can be pivoted upwards and downwards by 36 degrees.(Optional)

Acoustic soft top: this soft top reduces the interior noise level significantly. The outer fabric coating on the soft top has been acoustically optimised, while a butyl layer in place of the previous neoprene layer on the inside acts as a water barrier. Plus the intermediate felt layer is structured differently to that of the previous model.(Standard)

cd figure: this non-dimensional figure is the unit of measurement for a car model's drag coefficient. With a cd figure of 0.28 (with the roof closed), the new Mercedes-Benz E-Class Cabriolet is one of the world's most streamlined open-top cars. It is based on the E‑Class Coupé, which has a cd figure of 0.24, making it the world's most aerodynamic production car.

Belt feeder: Mercedes innovation for two-door cars. After the door is closed, the belt is extended towards the front occupant, making it easier to reach.(Standard)

Wind resistance: the product of the drag coefficient (cd figure) and the frontal area of a vehicle, indicated in m². Unit of measurement indicating how efficiently a vehicle cuts through the air.

Frontal area: this cross-sectional area of a body in flow direction is a key factor when measuring a car's wind resistance, alongside the cd figure. In the past, the frontal area was calculated by projecting the shadow of the body onto a transparent screen using a lamp positioned some considerable distance away. The outline was then depicted and used to calculate the individual segments of the entire area. Nowadays the frontal area is sensed using laser light barriers.

Thermography: a special camera is used to visualise the heat radiated by persons or objects. The basic principle at work here is as follows: at temperatures above absolute zero (i.e. minus 273 degrees Celsius), all objects essentially radiate heat. This thermal energy is infrared light with a wavelength that the human eye cannot perceive. The higher the temperature of the object, the more intense its infrared radiation.

Wind tunnel: in this testing area, fans or blowers create a flow of air, enabling testing of a vehicle's aerodynamic and aeroacoustic properties. The large wind tunnel owned by Daimler AG in Stuttgart-Untertürkheim has been in operation for almost 70 years and was the world's first installation of its kind. Regularly modified to ensure that it remains state-of-the-art, it offers testing possibilities at speeds of up to 250 km/h and, thanks to a turntable, flow angles of up to 180 degrees.

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