Consider flow at velocity U relative to a solid cylinder of radius R and length L whose axis is perpendicular to the approaching fluid, as in Fig. P6.6.

(a) Show how to calculate the drag if ℘(R, θ) and τ(R, θ) are known. Neglect the ends of the cylinder (i.e., assume that L ≫ R) and exclude from your expression any components of τ(R, θ) that must be zero.

(b) A set of pressure measurements obtained for Re = 1.86 × 10⁵ (Schlichting, 1968, p. 21) can be represented approximately as

Use this to calculate the contribution of form drag to C_D and compare your result with the information. What does this comparison show about the relative importance of form drag and friction drag on a cylinder at high Re?

Transcribed Image Text:

|- U y R Figure P6.6 Flow at velocity U past a long cylinder of radius R. X Ө