# Drag Coefficients

#### Summary

Drag coefficients (CD) in aerodynamics are drag forces normalized with a reference area, usually the frontal area, another projection area or the wetted area. Sometimes the reference area is not given, so the drag coefficient is a misleading figure.

The actual values of the CD of particular devices are confidential by nature. The drag force, instead, is more clearly identified.

All the data reported in the tables below must be read as averages. Each entry has its own order of approximation. The tables have been elaborated from a number of sources.

#### Description

Table 1 reports some typical values for widely studied bluff bodies.

Table 2 is a summary of typical drag coefficients of streamlined bodies.

Table 3 is a summary of drag data for airborne systems and road vehicles.

Table 4 reports a summary of drag data for a human being performing some well known physical activities.

Table 5 reports drag coefficients and total drag forces for some automobiles.

Table 6 reports data for other systems, including towers and tall buildings.

 Rough Shere (Re=) 0.4 Smooth Sphere (Re= [0] 0.1 Hollow semi-sphere opposite stream 1.42 Hollow semi-sphere facing stream 0.38 Hollow semi-cylinder opposite stream 1.2 Hollow semi-cylinder facing stream 2.3 Squared flat plate at 90° 1.17 Long flat plate at 90° 1.98 Open Wheel, rotating, h/D=0.28 0.58

 Laminar flat plate (Re=) 0.001 Turbulent flat plate (Re=) 0.005 Airfoil Section, minimum [1] 0.006 Airfoil Section, at stall [1] 0.025 2-Element Airfoil 0.025 4-Element Airfoil 0.05 Subsonic Aircraft Wing, minimum [2] 0.05 Subsonic Aircraft Wing, at stall [2] 0.16 Subsonic Aircraft Wing, minimum [3] 0.005 Subsonic Aircraft Wing, at stall [3] 0.09 Aircraft Wing (supersonic) n.a.

 Subsonic Transport Aircraft 0.012 Supersonic Fighter, M=2.5 0.016 Airship 0.020-0.025 Helicopter Download [4] 0.4-1.2 Sports Car 0.3 -0.4 Ecomony Car 0.4 -0.5 Pickup Truck 0.5 Tractor-Trailer, with fairings 0.6-0.7 Tractor-Trailer 0.7-0.9 Trailer alone 0.9 Racing Car [5] 0.65-1.10

 Man (upright position) 1.0 - 1.3 Ski jumper 1.2 - 1.3 Skier 1.0 - 1.1 Parachutist 1.0 - 1.4

Table 5: Drag coefficients for some passenger vehicles
Vehicle (class) CD CD × A (m²)
VW Polo (class A) 0.37 0.636
Ford Escort (class B) 0.36 0.662
Open Vectra (class C) 0.29 0.547
BMW 520i (class D) 0.31 0.649
Mercedes 300SE (class E) 0.36 0.785

 Wires and cables 1.0 - 1.3 Empire State Building 1.3 - 1.5 Eiffel Tower 1.8 - 2.0 Suspension Bridge N.A.

#### Notes

[0] See Speed Effects for details

[1] Approximate. Actual values strongly dependent on airfoil and Reynolds number.

[2] Rectangular wing of aspect-ratio 5.

[3] Wing NACA 64-210, aspect-ratio=9, taper=2.5, Re = 4.4 , M = 0.17.

[4] It is the drag coefficient for a helicopter in hover; depends on the type of fuselage and the number and type of free standing sub-parts (stubs, nacelles, wings, fuel tanks, weapons, etc.)

[5] Referred to the frontal area. If the reference area is the projected planform, the CD is much lower.

#### Selected References

• Hoerner SF. Fluid Dynamic Drag, Hoerner Fluid Dynamics, 1965.

• Clift R, Grace JR, Weber ME. Bubbles, Drops, and Particles, Academic Press, New York, 1978.

• Sovran G, Morel T, Mason WT (editors), Aerodynamic Drag Mechanisms of Bluff Bodies and Road Vehicles, Plenum Press, New York, 1978 (ISBN 0-306-31119-4).

[Top of Page]