Abstract
Dispersion of plant pathogens, such as rust spores, is responsible for a
large portion of global crop production loss every year, in addition to the
threat they pose to human health. However, the release mechanism of pathogens
and other allergic particles from flexible plant surfaces into canopy
turbulence has not been understood well. Focusing on the phenomenon of
increased air-borne aerosols after rainfall, the present study elucidates how
the coupling of leaf elasticity and drop momentum directly modulates
surrounding airflow and spore transport. We discovered that vortex generated
from the sharp edge of a leaf during drop impacts shed in dipoles and generate
stream flows that enable pathogen escapes. To understand the mechanics, we
first built and experimentally validated a joint model of impact mechanics and
airfoil potentials to parametrically link drop momentum, vibration speed, and
dispersion capacity. Then with Lagrangian diagnostics, we uncovered different
sets of coherent structures around the leaf, providing a dynamical description
for how spores escape during rainfall. The work proposes here a stand-alone,
direct dispersion mechanics that incorporates the role of plant substrate
elasticity and emergent flow coherence. The physical insights extracted here
can help build physical-informed analytics models for local crop disease
management.