Question

Ex.3 /35 A Cessna 172 has a cruise speed V-226 km/h and weight W-1,000Kg. The wing area is S-16mt with a wing span b-1lm Assuming the wing rectangular, what is the Reynolds number at an altitude z-1,000m. A model of this airplane, scaled by a factor of 2, is tested in a wind tunnel at sea level. What should be the velocity in the wind tunnel to have dynamics similarity (neglect Mach number effects). What will be the lift measured by the force balance in the wind tunnel? (at sea level the density is p-1.225 Kg/m', the viscosity is F-HATZ u-1.789 1053 Ns/m; at z-1,000m the density is p-1.112 Kg/m3, the viscosity is H-1.758 10 Ns/m2

Answer 1

w= 1000 b=11m Reyn.ld's no. R. fYL = 1.112.6 2.2LL 1, = s776 97.632 1758x IO- he = 5.776 x 10. 15-9 1.2교 5 758 X10 0.279% 2 x 1-112× 6278 x 16 a. 0.2718 =