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The reference area depends on what type of drag coefficient is being measured. For automobiles and many other objects, the reference area is the projected frontal area of the vehicle. This may not necessarily be the cross-sectional area of the vehicle, depending on where the cross-section is taken.
The term drag area derives from aerodynamics, where it is the product of some reference area (such as cross-sectional area, total surface area, or similar) and the drag coefficient. In 2003, Car and Driver magazine adopted this metric as a more intuitive way to compare the aerodynamic efficiency of various automobiles.
In mechanics and aerodynamics, the drag area of an object represents the effective size of the object as it is "seen" by the fluid flow around it. The drag area is usually expressed as a product , where is a representative area of the object, and is the drag coefficient, which represents what shape it has and how streamlined it is.
Aircraft use the wing area (or rotor-blade area) as the reference area, which makes for an easy comparison to lift. Airships and bodies of revolution use the volumetric coefficient of drag, in which the reference area is the square of the cube root of the airship's volume. Sometimes different reference areas are given for the same object in ...
A drag coefficient can also be calculated mathematically: = [8] where: C d, drag coefficient., density of the projectile. v, projectile velocity at range. π (pi) = 3.14159... d, measured cross-sectional diameter of projectile; or
is the reference area. The drag coefficient is used to compare the solutions of different geometries by means of a dimensionless number. A drag count is more user-friendly than the drag coefficient, as the latter is usually much less than 1. A drag count of 200 to 400 is typical for an airplane at cruise. [4]
is the drag force, which is by definition the force component in the direction of the flow velocity, is the mass density of the fluid, [61] is the flow velocity relative to the object, is the reference area, and is the drag coefficient – a dimensionless coefficient related to the object's geometry and taking into account both skin friction ...
1 References. Toggle the table of contents ... is the drag coefficient, is the frontal area, and ... is the inverse of the ballistic coefficient, and its unit is area ...