From
``insect” hovering to ``continental” drift – bio and
geo-inspired archetypes in fluid-structure interactions
Courant Institute of Mathematical Sciences
NYU
While insects hover with apparently high efficiency
and stability, our understanding of the underlying mechanisms is poor.
Here, I study a stripped-down model system of insect hovering – a
simple rigid body that has an up-down asymmetry, interacting with an
oscillating airflow. I find that this body hovers freely and stably. I
show that quasi-steady theory, which is widely applied to fixed-wing
aircraft, can only account for a fraction of the produced lift. Besides
having efficient lift production, the hovering motion is also
surprisingly stable and robust, lasting for thousands of oscillation
periods without any active control. To understand this I present flow
visualizations that show how vortices shed due to the unsteady flow
contribute to both efficient lift production and stable hovering.
I will also discuss an experiment that studies the interactions between
a freely moving, floating boundary and a thermally convective fluid
underneath. The aim is to investigate the essentials of the interplay
between large continents and a convective mantle. Very rich dynamics of
the floating boundary is observed, and can be understood through the
heat buildup beneath the continent (the "thermal blanket" effect in
geophysics), and its feedback onto the flow.
These studies on the archetypical systems may shed light on the insect
hovering and continental drift in Nature.