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Resistance Calculations (Turbulency)

There are almost an infinite number of different forms, but for the present the above examples will fill our purpose. As an example in showing how greatly the form of an object influences its resistance, we will work out the resistance of a flat plate and a spherical ended cone, both having the same presented diameter. The cone is placed so that the spherical end will face the air stream. The area A of both objects will be: 0.7854 × 2 × 2 = 3.1416 square feet. With an assumed wind velocity of 100 miles per hour, the resistance of the circular flat disc will be: R= KAV²=000282 × 3.1416 × (100×100) = 87.96 lbs. For the cone, R = KAV²=0.000222 × 3.1416 × (100 × 100) = 6.97 lbs. From this calculation it will be seen that it is advisable to surround the object with a spherical cone shaped body rather than to present the flat surface to the wind. In the above table the value of K is given for two positions of the spherical based cone, the first is with the apex toward the wind, and the second condition gives the value with the base to the wind. With the blunt end forward, the resistance is about one-half that when the pointed apex enters the air stream. This is due to the taper closing up the stream without causing turbulence.