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When a body is set in motion in a fluid atmosphere, a force of resistance, the aerodynamic drag, acts on it. Today, aerodynamics influence the body design in the development of nearly all new automobiles. Before presenting the components of aerodynamic drag, however, an overview of the basics of aerodynamics is dealt with.

Initially, a friction-free flow is considered. In the transverse plane, the potential flow around a cylinder is symmetrical in the streamed area in the flow direction and perpendicular to it. This results in two ram points: one in the front and the other behind the cylinder where according to Bernoulli the entire kinetic energy is transformed into potential energy (ram pressure). According to the Potential Theory a loss-free and symmetrical return to the initial state before the body was subjected to a flow is achieved. In this case, as an integral value of the pressure distribution over the area, the aerodynamic forces having acted on a body sum up to zero. According to this, there is no flow separation or turbulence in the flow area.