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Drag coefficients in fluids with Reynolds number approximately 10 4 [1] [2] Shapes are depicted with the same projected frontal area. In fluid dynamics, the drag coefficient (commonly denoted as: , or ) is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment, such as air or water.
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 ...
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.
The product of drag coefficient and area – drag area – is represented as CdA (or C x A), a multiplication of Cd value by area. 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.
Sometimes a body is a composite of different parts, each with a different reference area (drag coefficient corresponding to each of those different areas must be determined). In the case of a wing, the reference areas are the same, and the drag force is in the same ratio as the lift force. [14]
Another method of determining trajectory and ballistic coefficient was developed and published by Wallace H. Coxe and Edgar Beugless of DuPont in 1936. This method is by shape comparison an logarithmic scale as drawn on 10 charts. The method estimates the ballistic coefficient related to the drag model of the Ingalls tables.
A is a reference area, e.g. the cross-sectional area of the body perpendicular to the flow direction, V is volume of the body. For instance for a circular cylinder of diameter D in oscillatory flow, the reference area per unit cylinder length is A = D {\displaystyle A=D} and the cylinder volume per unit cylinder length is V = 1 4 π D 2 ...
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]