Drag Coefficient

A dimensionless value that allows the comparison of shape and orientation of different bodies.


The force on an object due to aerodynamic drag can be calculated using:

where
F = aerodynamic drag force [N]
Cd = drag coefficient
A = frontal area [m2]
ρ = density of fluid [kgm-3]
v = velocity of object relative to fluid [ms-1]
Re = Reynolds number


Circular flat plate
Cd = 1.12
Re ~ 1e6
A = πd2/4
Sphere
Cd = 0.45
Re < 2e5
A = πd2/4


Cd = 0.2
Re > 2e5
A = πd2/4
Solid Hemisphere
Cd = 0.38
Re = 1e3
A = πd2/4
Solid Hemisphere
Cd = 1.17
Re = 1e3
A = πd2/4
Miscellaneous Objects
CdObject
1.0 to 1.4skydiver
1.0 to 1.3person standing
0.9bicycle
0.7 to 1.1formula one race car
0.6bicycle with faring
0.35 to 0.45light truck
0.25 to 0.35car
0.05airfoil
0.15airfoil at stall

See also: Drag, Frontal Area, Pressure Coefficient, Reynolds Number, Vehicle Aerodynamic Drag.

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Subjects: Aerodynamics Fluid Dynamics


Weblinks:
Aerospaceweb.org - Golf Ball Dimples The aerodynamics of spheres and spheres with dimples - more commonly known as golf balls.