Payload
A lightweight parachute is being designed for military use. Its diameter D is 20 ft and the total weight W of the falling payload, parachute, and equipment is 145 lbf. The design terminal settling speed Vt of the parachute at this weight is 18 ft/s. A one-twelfth scale model of the parachute is tested in a wind tunnel. The wind tunnel temperature and pressure are the same as those of the prototype, namely 60°F and standard atmospheric pressure. (a) Calculate the drag coefficient of the prototype. (Hint: At terminal settling speed, weight is balanced by aerodynamic drag.) (b) At what wind tunnel speed should the wind tunnel be run in order to achieve dynamic similarity? (c) Estimate the aerodynamic drag of the model parachute in the wind tunnel (in lbf).
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