The flow characteristics of dandelions with different pappus angles

The porous and fluffy pappus structure of the dandelion is crucial for its stable flight. The pappus angle can be adjusted automatically in response to humidity to regulate flight capabilities. This study investigated the effect of pappus angle on flight dynamics using custom-made molds to fabricate dandelions with varying pappus angles. Aerodynamic drag was measured across wind speeds ( 0.1 ∼ 0.8 m s − 1 ) using an air-bearing-based drag balance, while a hot-wire anemometer and particle image velocimetry analyzed wake vortex structures. Results showed that dandelions exhibit higher drag coefficients at low wind speeds, with larger pappus angles increasing drag and wake stability at higher Reynolds numbers. Smaller pappus angles led to lower local porosity, stronger shear effects, and rapid wake instability. Natural dandelions demonstrated superior vortex growth and spatial stability at high Reynolds numbers compared to artificial ones, highlighting the advantages of their complex three-dimensional pappus structure. Additionally, lateral vortex diffusion was constrained when the pappus angle exceeded 140 ° , limited by local porosity. These findings could inspire efficient unpowered aircraft designs.