Which drag develops from the frictional resistance of blades passing through the air and increases moderately with airspeed?

Which drag develops from the frictional resistance of blades passing through the air and increases moderately with airspeed?

• A. Drag
• B. Induced Drag
• C. Form Drag
• D. Profile Drag

Answer: (D)

The frictional resistance of blades moving through air is called profile drag. This is a type of parasite drag tied to the blade’s surface—skin friction from air rubbing against the blade and the pressure distribution around its shape. As the blade moves faster, the relative airspeed over the surface increases, raising the shear forces and the resulting drag, so profile drag grows with airspeed. Induced drag, by contrast, comes from lift generation and actually decreases as speed increases, because higher speed reduces the influence of finite-span vortices. Form drag is the pressure drag from the blade’s shape and flow separation, which is also present but originates from pressure differences rather than skin friction. The description focusing on frictional resistance points specifically to profile drag.

The frictional resistance of blades moving through air is called profile drag. This is a type of parasite drag tied to the blade’s surface—skin friction from air rubbing against the blade and the pressure distribution around its shape. As the blade moves faster, the relative airspeed over the surface increases, raising the shear forces and the resulting drag, so profile drag grows with airspeed.

Induced drag, by contrast, comes from lift generation and actually decreases as speed increases, because higher speed reduces the influence of finite-span vortices. Form drag is the pressure drag from the blade’s shape and flow separation, which is also present but originates from pressure differences rather than skin friction. The description focusing on frictional resistance points specifically to profile drag.