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

C_d A,

where

A

is a representative area of the object, and

C_d

is the drag coefficient, which represents what shape it has and how streamlined it is. The drag coefficient plays a role in Reynold's drag equation, :

F_d=\frac\ \rho\ C_d A\ v^2.

Here,

F_d

is the drag force,

\rho

the density of the fluid, and

v

the speed of the object relative to the fluid.

See also