Hoerner (Ref. 12) plots the drag of a flag in winds, based on total surface area 2bL, in the figure at right. A linear approximation is CD ≈ 0.01 + 0.05L/b, as shown. Test Reynolds numbers were 1E6 or greater. (a) Explain why these values are greater than for a flat plate. (b) Assuming sea-level air at 50 mi/h, with area bL = 4 m2, find the proper flag dimensions for which the total drag is approximately 400 N.

Transcribed Image Text:

b Hoerner's 02 D 0016 Ivn b-4 V 80 tsee 00.05 L/b