Approach velocity

The flow velocity is the speed at which a gas or liquid flows towards a solid body before it influences the flow .

The dynamic lift and the flow resistance are proportional to the square of the flow velocity over a wide speed range . Direction to the incident flow (angle of attack) refers to a unique axis or plane of the body when the wing z. B. on the chord of a profile :

• The angles in the projection on the longitudinal section are called the angles of attack ,
• Angle in the projection onto the base area as a sliding angle .

In the case of cars , the sliding angle, the z. B. is caused by cross wind , on the center plane of the vehicle. In the wind tunnel , six components are measured depending on the angle of attack:

• resistance
• Lateral force
• boost
• Roll moment
• Pitching moment
• Yaw moment.

From the forces and moments are each dimensionless coefficients formed. The frontal area is the reference value for the forces and the product of the frontal area and wheelbase for the moments . The reference point for the moments is on the roadway and in the middle with regard to the wheelbase and track width.

literature

• Thomas Schütz: Hucho - aerodynamics of the automobile . Springer Vieweg, Wiesbaden 2013, ISBN 978-3-8348-2316-8 .