From ``insect” hovering to ``continental” drift – bio and geo-inspired archetypes in fluid-structure interactions


Bin Liu


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.