Characterization of milkweed-seed gust response

Area of Science:

• Fluid dynamics
• Aerodynamics
• Biomimetics

Background:

• Plants use bristled seeds for wind dispersal.
• Milkweed seeds are near-spherical and porous.

Purpose of the Study:

• Investigate the gust response of milkweed seeds.
• Determine if porous seeds have unique aerodynamic properties.

Main Methods:

• Gust-response experiments in an unsteady wind tunnel.
• Optical motion-tracking and particle image velocimetry (PIV).

Main Results:

• Seed acceleration ratio matches theoretical predictions and soap bubbles.
• Minimal flow through the porous seeds was observed.
• Instantaneous drag exceeded that of a solid sphere during initial acceleration.

Conclusions:

• Porosity does not degrade aerodynamic performance in milkweed seeds.
• Porous seeds generate enhanced drag during initial flow acceleration.
• This mechanism supports effective wind-borne dispersal.