Unlock document.
This document is partially blurred.
Unlock all pages and 1 million more documents.
Get Access
4.14
4.15 (a) Re =
At 18,000 ft, from Appendix E, ρ∞ = 1.3553 x 10-3 slug/ft3. From Section 1.11,
μ∞ = 3.7373 x 10-7 slug/(ft)(s). Assuming that μ varies as the square root of the
Hence,
(b) Modeling the airfoil with a flat plate for the estimation of skin-friction
drag, we have from Eq. (4.88),
This is for one side of the plate. Taking into account both the top and bottom
surfaces,
The total profile drag coefficient for the airfoil section is given experimentally as
________________________________________________________________
4.16 Using Figure 4.44 as a guide, first calculate xcr = x1
Since c = 8.33 ft, then x1 = 0.111 (8.33) = 0.9256 ft. Over the laminar portion of
the flow, from Eq. (4.86)
For a turbulent flow over the length x1,
Referring to Eq. (4.92), the net skin friction coefficient over one side of the plate
is,
Taking into account both sides of the plate
The percentage of profile drag coefficient due to pressure drag is
