A lightweight parachute is being designed for military use (Fig. P7–40E). Its diameter D is 24 ft and the total weight W of the falling payload, parachute, and equipment is 230 lbf. The design terminal settling speed V_t 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. 

(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).

FIGURE P7–40E

Transcribed Image Text:

Payload D- V₂