Chapt06

649 we obtain the formula relating mean velocity to

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Unformatted text preview: Effect of Rough Walls It was not known until experiments in 1800 by Coulomb [6] that surface roughness has an effect on friction resistance. It turns out that the effect is negligible for laminar pipe flow, and all the laminar formulas derived in this section are valid for rough walls also. But turbulent flow is strongly affected by roughness. In Fig. 6.9 the linear viscous sublayer only extends out to y yu*/ 5. Thus, compared with the diameter, the sublayer thickness ys is only ys 5 /u* 14.1 (6.60) d d Red f 1/2 umax Parabolic curve V (a) V umax | v v Fig. 6.11 Comparison of laminar and turbulent pipe-flow velocity profiles for the same volume flow: (a) laminar flow; (b) turbulent flow. (b) | e-Text Main Menu | Textbook Table of Contents | Study Guide 6.4 Flow in a Circular Pipe 347 0.10 0.08 ∋ = 0.0333 d 0.06 0.0163 0.04 0.00833 f 0.00397 ∆B u u* o Sm 0.00198 64 Red 0.00099 0.02 oth h ug Ro Eq. (6.55a) Eq. (6.54) ≈1n ∋ + log 0.01 yu* v 10 3 10 4 10 5 10 6 Red (a) (b) Fig. 6.12 Effect of wall roughness on t...
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This note was uploaded on 10/27/2009 for the course MAE 101a taught by Professor Sakar during the Spring '08 term at UCSD.

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