A light parachute for military purposes is being designed. Its diameter is 7.3 m, test load, parachute and rig weight is 1023 N. For this weight, the limit descent speed Vt = 6.1 m / s, which is taken as a basis in the design of the parachute. The 1/12 scale model will be tested in the wind tunnel and the temperature and pressure of the tunnel are the same as that of the prototype. (15.5 ºC and standard atmospheric pressure) a) Calculate the resistance coefficient of the prototype. (Hint: At the limit descent speed, the weight
A light parachute for military purposes is being designed. Its diameter is 7.3 m, test load, parachute and rig weight is 1023 N. For this weight, the limit descent speed Vt = 6.1 m / s, which is taken as a basis in the design of the parachute. The 1/12 scale model will be tested in the wind tunnel and the temperature and pressure of the tunnel are the same as that of the prototype. (15.5 ºC and standard atmospheric pressure)
a) Calculate the resistance coefficient of the prototype. (Hint: At the limit descent speed, the weight is balanced by the aerodynamic resistance.)
b) At what speed should the wind tunnel be run to achieve dynamic similarity?
c) Calculate the aerodynamic resistance of the model parachute in the wind tunnel. Density of air at 15.5 ºC and standard atmospheric pressure ρ = 1.22 kg / m3 viscosity, µ = 8.16x10-6 kg / m.s will be taken.
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