Английская Википедия:Drag count

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A drag count is a dimensionless unit used by aerospace engineers. 1 drag count is equal to a <math>C_d</math> of 0.0001.[1][2]

As the drag forces present on automotive vehicles are smaller than for aircraft, 1 drag count is commonly referred to as 0.0001 of <math>C_d</math>.

Definition

A drag count <math>\Delta C_\mathrm d\,</math> is defined as:

<math>\Delta C_\mathrm d = 10^{4} \dfrac{2 F_\mathrm d}{\rho v^2 A}\, ,</math> [3]

where:

<math>F_\mathrm d\,</math> is the drag force, which is by definition the force component in the direction of the flow velocity,Шаблон:Efn
<math>\rho\,</math> is the mass density of the fluid,Шаблон:Efn
<math>v\,</math> is the speed of the object relative to the fluid, and
<math>A\,</math> 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] A reduction of one drag count on a subsonic civil transport airplane means about Шаблон:Cvt more in payload.[5]

Notes

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References

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See also


Шаблон:Fluiddynamics-stub