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Unformatted text preview: Solutions HW5 ENG 103 Fall 2011 P5.72 A one-twelfth-scale model of a large commercial aircraft is tested in a wind tunnel at 20 C and 1 atm. The model chord length is 27 cm, and its wing area is 0.63 m 2 . Test results for the drag of the model are as follows: V, mi/h 50 75 100 125 Drag, N 15 32 53 80 In the spirit of Fig. 5.8, use this data to estimate the drag of the full-scale aircraft when flying at 550 mi/h, for the same angle of attack, at 32,800 ft standard altitude. Neglect Mach number differences between model and prototype. Solution : Compute the model drag coefficients and Reynolds numbers, plot them, and extrapolate in the spirit of Fig. 5.8 of the text. For the first point, 50 mi/h = 22.35 m/s. At 20 C and 1 atm, = 1.20 kg/m 3 and = 1.8E-5 kg/m-s. Compute the first dimensionless data point: Do this for all four model data points: Re c 402,000 604,000 805,000 1,006,000 C D 0.0794 0.00753 0.00702 0.00678 Now plot them and extrapolate to the prototype Reynolds number. Now plot them and extrapolate to the prototype Reynolds number....
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