ABSTRACT
Air separators classify seed according to their aerodynamic behavior in a moving air stream. A seed (which is a dry particulate solid) reacts to a flowing air stream according to its terminal velocity, which is the maximum or terminal speed it can attain if it falls freely through still air. A seed’s terminal velocity depends on its shape, size, surface texture, and specific gravity (weight or density). If the air stream is moving upward, the air velocity is at the seed’s terminal velocity when the seed sits suspended at a stationary position (i.e., it does not move up or down) in the flowing air. If the airspeed is higher than the seed’s terminal velocity, the seed is blown upward; if the seed’s terminal velocity is higher than the airspeed, the seed falls down through the flowing air stream.
