Skin friction is defined as?

Skin friction is defined as?

• A. Air clinging to the surface of the aircraft
• B. Drag from the body traveling through air
• C. Weight
• D. Thrust

Answer: (A)

Skin friction is the drag produced by viscous shear in the boundary layer as air flows over the aircraft surface. The air in contact with the surface sticks due to viscosity, and the adjacent layers slide past one another, generating tangential forces that oppose motion. This frictional drag is what we call skin friction and it contributes to the overall parasite drag, increasing with surface area, speed, and surface roughness, and depending on whether the boundary layer is laminar or turbulent. The idea of air clinging to the surface captures this viscous interaction. The other concepts describe different forces: drag from the body through the air refers to total drag (including pressure effects), weight is gravity, and thrust is propulsion.

Skin friction is the drag produced by viscous shear in the boundary layer as air flows over the aircraft surface. The air in contact with the surface sticks due to viscosity, and the adjacent layers slide past one another, generating tangential forces that oppose motion. This frictional drag is what we call skin friction and it contributes to the overall parasite drag, increasing with surface area, speed, and surface roughness, and depending on whether the boundary layer is laminar or turbulent.

The idea of air clinging to the surface captures this viscous interaction. The other concepts describe different forces: drag from the body through the air refers to total drag (including pressure effects), weight is gravity, and thrust is propulsion.