Equations · equation
Drag Equation
Fluid Dynamics · 1876
- Equation
- F_d = ½ ρ v² C_d A
- Field
- Fluid Dynamics
- Symbols
- F_d drag force · ρ fluid density · v speed relative to the fluid · C_d drag coefficient, found by experiment · A frontal area
- Year
- 1876
Significance
At the speeds of cars, birds and turbine blades drag goes with the square of the speed — twice as fast, four times the force, eight times the power. The drag coefficient sweeps up everything shape and Reynolds number do: about 0.3 for a modern car, 1.0 for a cyclist upright, 0.04 for an aerofoil. Rayleigh gave it this form in 1876; the v² was Newton's.
Referenced by
equation
impact
machine
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