Aerodynamics, Basic Function - GF88.00-P-9900A

Model all (CAR) 

Courtesy of MERCEDES-BENZ USA

Illustration of streamlining and aerodynamic drag 

Overview 

This document contains information on:

• General 
• Function 

General 

In aerodynamics, the best possible streamlining keeps the vehicle's aerodynamic drag as low as possible; optimizing driving characteristics with respect to the resulting air flow. Vehicle design, "flow-controlling" detachable parts, as well as the consumption of combustion engines or the range of electric vehicles are also directly relevant in this connection. The resistance is made up of the cross-sectional area of a body that opposes the wind, and the drag coefficient. This value describes how easily the wind can flow over a body and is between 0.05 (for the best shaping) and 1 (for a cube). The less resistance the vehicle offers, the more energy is saved.

The portion of aerodynamic drag in the overall vehicle resistance increases quadratrically as vehicle speed increases. As a result, the aerodynamic drag is responsible for significantly more than half of energy consumption during longer trips at higher speeds. The individual design elements of the body, as well as the additional front, rear, and side spoilers have a significant influence on aerodynamics.

The drag coefficient can be reduced by various measures, for example on the diffuser, the front and rear apron, and the installation of running boards on the longitudinal members. These measures reduce fuel consumption in combustion engines and increases the range of electric vehicles on account of the electrical energy available.

In electric vehicles, the fully closed and smooth underbody also improves air flow under the vehicle. Furthermore, the large air volumes required for combustion engines are not needed. With the active air control system, the slats in the radiator grille can be completely closed as required, so the air slides forward and downward on the vehicle.

The installation of spoilers and wings on the vehicle leads to a reduction in lift force, thus increasing the contact pressure of the vehicle on the road. The airstream is routed around the vehicle in such a way that the air pressure under it drops. As a result, handling quality at high speeds, cornering stability or braking distance, are improved.

The following types of spoilers can be distinguished:

• Front spoiler
• Rear spoiler
• Wheel spoiler
• Side spoiler

Function 

The air is directed over the vehicle, from the radiator grille, via the hood, windshield, and roof. The main task of the spoiler is to direct the oncoming air in an upward direction. This ensures that contact pressure is exerted on the vehicle. On the one hand, this makes for improved handling quality, on the other, it lowers fuel consumption.

The effect described only applies at higher speeds.