What is skin friction in aerodynamics

What is profile resistance?

The composition of the total resistance as shown below:

Thanks to DRAGBUSTERS ... This document can solve this question and analyze the air resistance in detail.

Profile resistance definition: The Profile drag is the drag created by the frictional drag of the blades flowing through the air. It does not change significantly with the angle of attack of the wing section, but increases moderately with increasing airspeed. Taken from here.

Definitions of Profile resistance as in dictionaries:

That part of the wing drag that is due to friction and turbulence in the fluid that would be missing if it were not viscous

The part of a wing or aircraft's drag that results directly from its profile and skin friction (ie, the part that is not attributable to lift).

By reading this ... (in the fifth paragraph)

Definition of form resistance: The Resistance, which depends on the shape of the aircraft is called Designated form resistance .

The following definition has been adopted from here.

Profile resistance or sometimes also called form drag, is the drag caused by the separation of the boundary layer from a surface and the wake created by this separation. It mainly depends on the shape of the object. Form or pressure resistance is caused by the air flowing over the aircraft or the airfoil.

Finally, the most common types of drag are:

Parasitic resistance, consisting of

Form resistance which is the result of aerodynamic drag due to the shape of the aircraft,

Skin friction resistance due to the smoothness or roughness of the surfaces of the aircraft, and

Interference resistance, which can occur when surfaces with different properties meet (e.g. wing and fuselage).

Induced resistance, which is a secondary effect of the generation of lift, and

Wave resistance, which comes into play when shock waves occur near the aircraft surface in transonic and supersonic flight.

Taken from this Skybrary article which describes the types of resistance very well.

TomMcW

Herein lies the riddle. I asked the question after reading most of these articles. They each give a different definition. Your first example essentially contains the definition of skin resistance. In your second example, the skin resistance is first defined, then changed and defined as the sum of skin and form resistance. The third point defines the pulling of forms and not addressing the profile. The fourth says it's another name for shape drag. And Skybrary doesn't mention any profile at all. So my question is still not answered.

Peter Kämpf

Why should the induced drag flatten out at low speed? These two graphs look very wrong near the Y axis. Other than that, your answer is spot on.

Lidakis Emmanuel

Thank you for your comments, the answer will be updated with new content. Hope this helps now. If there is anything else you need or something is wrong, please let me know.

TomMcW

Ok, I think the flowcharts will be key to understanding. +1 for those. Can you look at the other definitions in your answer? Some seem to conflict with the diagram and should probably be cut out. For example, it is clearly not synonymous with shape drag, and one of the definitions says just that

Lidakis Emmanuel

Yes, of course there is a sense of contradiction between the definitions, but at the same time when you see the second flowchart, imho, the definition is not really completely wrong, but it depends on the perspective of taking a UNIT (profile or shape or all together) for one measurement, and of course that depends on the perspective of 2D and 3D. I am going to edit this to look correct, but if you still think this is incorrect please point out to me that the section you think needs an edit.