Aerodynamics Properties of Silflower Seed: Effect of Moisture and Seed Morphology

Highlights Terminal velocity increased linearly with moisture (10%–15% d.b.) for both silphium seed types. Wingless SP-16 type exhibited higher terminal velocity and densities than winged CP-16 type. Drag coefficient decreased as moisture content increased for CP-16, likely due to the presence of winglets. SP-16’s higher density and geometric mean suggest better processing in standard combines. ABSTRACT. Silflower (Silphium integrifolium), a perennial wildflower native to the central United States, is a potential sustainable oilseed crop due to its drought tolerance and deep root systems. However, its unique seed morphology, characterized by irregular shapes and wing-like structures, poses challenges for mechanical harvesting and processing, necessitating a better understanding of its aerodynamic properties. This study investigates the effects of moisture content (ranging from 10% to 15% d.b.) on the terminal velocity, drag coefficient, and Reynolds number of two Silphium seed accessions: CP-16 (with wing-like features) and SP-16 (without winglets). A custom-built vertical column unit was constructed and used for the experiment. The results showed that terminal velocity increased linearly with moisture content for both accessions (SP-16: 4.78-6.43 m/s; CP-16: 2.39-3.16 m/s). The higher terminal velocity and bulk density of the wingless SP-16 accession indicate it may process more efficiently with standard combines and threshers. Drag coefficients showed complex interaction with moisture content, decreasing for CP-16 but varying inconsistently for SP-16. The Reynolds numbers increased with moisture for both accessions, indicating changes in flow dynamics. Analysis of variance confirmed significant effects of moisture content and accession type on aerodynamic properties (p < 0.0001). The findings highlight the need for breeding programs to optimize seed traits that improve terminal velocity and reduce aerodynamic drag, particularly in the winged CP-16 accession.