유체역학 6판 조광래 외2명 솔루션(3-6)

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유체역학 6판 조광래 외2명 솔루션(3-6)

목차

Chapter 4 • Differential Relations
for a Fluid Particle

Chapter 5 • Dimensional Analysis
and Similarity

Chapter 6 • Viscous Flow in Ducts

본문내용

6.3 For a thin wing moving parallel to its chord line, transition to a turbulent boundary layer occurs at a “local” Reynolds number Rex, where x is the distance from the leading edge of the wing. The critical Reynolds number depends upon the intensity of turbulent fluctuations in the stream and equals 2.8E6 if the stream is very quiet. A semiempirical correlation for this case [Ref. 3 of Ch. 6] is crit1/221(113.25)Re0.00392xζζ−++≈
where ζ is the tunnel-turbulence intensity in percent. If V = 20 m/s in air at 20°C, use this formula to plot the transition position on the wing versus stream turbulence for ζ between 0 and 2 percent. At what value of ζ is xcrit decreased 50 percent from its value at ζ = 0?
Solution: This problem is merely to illustrate the strong effect of stream turbulence on the transition point. For air at 20°C, take ρ = 1.2 kg/m3 and μ = 1.8E−5 kg/m⋅s. Compute Rex,crit from the correlation and plot xtr = μRex/[ρ(20 m/s)] versus percent turbulence:

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chapter6.pdf
chapter4.pdf
chapter5.pdf