The Aerodynamics of a Falling Hopea Odorata Seed

Abstract

The double-winged seeds of the Hopea odorata tree generate an auto-rotating motion from their elongated sepals as they fall. The flight dynamics of the seed were analyzed using high-speed video. Terminal velocity and spin frequency were measured as a function of changing seed mass. Both were shown to increase with increasing seed mass. It was also shown that lift force provided 60-85% of the retarding force generated during descent and that the coefficient of lift for the seed decreased from approximately 0.7 to 0.3 as spin frequency increased.

Keywords

• hopea odorata
• winged seed
• mass
• terminal velocity
• spin frequency
• coefficient of lift