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A designer proposes eliminating skin-friction drag entirely by perfect streamlining. The proposal is

  • A.Achievable only in laminar flow
  • B.Achievable at low Reynolds number
  • C.Unachievable; streamlining attacks pressure drag
  • D.Achievable if the body is long enough

Answer: C

Streamlining works on the pressure term by keeping the flow attached, and it typically raises the wetted area and therefore the friction. So long as the fluid is viscous and the surface has area, skin friction cannot be removed; it can only be traded against something larger.

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