Talk:Skin friction drag: Difference between revisions

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Revision as of 22:08, 4 May 2016

I don't know exactly what this needs changing to to fix it, but the bottom section titled "drag" is a) apparently in pounds and b) Has Cf on both sides of the equation, leading to them cancelling and you being left with a load of variables multiplied together equaling one. I see these as problems with need fixing.

Turbulent drag is not supposed to be less than laminar drag, with every other circumstances being the same

Article says: " Turbulent flow suggests a faster rate of flow due to velocity increase and/or viscosity decrease relative to laminar flow. This results in a thinner boundary layer which, relative to laminar flow, depreciates the magnitude of friction force as the fluid flows over the object "

A) That's clearly not the case since a thinner boundary layer would mean a greater tangential velocity gradient at the solid-fluid boundary, thus, greater friction.

B) In addition to that, a turbulent boundary layer has a steeper tangential velocity profile just because it's turbulent: the chaotic movement enhances the momentum diffusion.

C) Finally, the turbulent boundary layer is always thicker than a laminar boundary layer, et ceteris paribus.

   This also increases the displacement thickness, and through it, the pressure drag.  — Preceding unsigned comment added by 94.21.58.239 (talk) 21:02, 4 May 2016 (UTC)[reply]

Possibly misleading equation

In aeronautics, the skin friction coefficient is given per wing planform area, not wetted area. — Preceding unsigned comment added by 94.21.58.239 (talk) 21:06, 4 May 2016 (UTC)[reply]

False statement about turbulent skin friction drag contribution to parasitic drag

Article says: "This suggests that the total parasitic drag observed in turbulent flow is minimally impacted by skin friction drag."

Actually, the laminar flow is more prone to separate, giving proportionally bigger form drag and smaller skin friction drag. In a turbulent case, it's the other way around. — Preceding unsigned comment added by 94.21.58.239 (talk) 21:17, 4 May 2016 (UTC)[reply]

Vague introduction

Not only lifting bodies have skin friction drag, but every solid body in a fluid flow. Fluid skin friction drag is not like solid friction, it emerges through shear forces caused by velocity gradients, because of the no-slip condition.