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Question: sketch the velocity profiles for a laminar and turbulent boundary...

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Sketch the velocity profiles for a laminar and turbulent boundary layer and discuss salient features. (b) 5 marks] Boeing 757 Figure Q5 unmodified wing NLF plove 05 m by 3.0 m (c) In the 1980s, NASA conducted a series of flight tests using a glove wrapped around the wing of a Boeing 757 transport immediately outboard of the starboard (right) engine, as illustrated in Figure Q5. This glove, which modified the contour of the wing, was designed to promote extensive natural laminar flow (NLF) at high altitude and Mach numbers. The tests were conducted at a Mach number of 0.7 at an atitude of 41,000 feet. The glove had an effective chord length of 0.5 m and was 3.0 m in span. Data at 41,000 feet ρ-o288 kgms, T-216 K, μ-1.48 x 10° kgms Using the flat-plate skin friction drag coefficients, n for laminar and turbulent boundary layers given in the appendix of formulae, estimate the drag force due to skin friction on the glove surface for both () laminar and (i) turbulent flows. Use L 0.5 m as the effective chord. Discuss your answers with reference to the boundary layer [10 marks] (d) Irrespective of whether the flow is laminar or turbulent, explain why conventional aircraft (such as the Boeing 757) are limited to cruise efficiently at a Mach number < 0.88.

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