The researchers ran three different simulations of this mathematical butterfly, and found that the insect used the forces from teensy whirlpools in the air created during each flap of its wings to create lift. They noticed that the butterfly's flight was bumpy as it moved through the air, with lots of ups and downs as it pushed itself forward.
There were some surprises in the tiny flows of air surrounding the butterflies. "The flow around the butterfly is much more turbulent than expected," says Yokoyama.
Using data from observations of butterfly flight in wind tunnels, the
researchers conducted three different types of simulations with their
model that were defined by the position and attitude of the thorax:
tethered (where the thorax is fixed), prescribed (where the thorax is
programmed to move in an expected manner) and free-flight (where the
thorax movement is unrestricted). They found that their mathematical
butterfly did -- as predicted -- make use of the tiny, swirling vortices
that form in the direction of travel during a downward flap, pushing
air down and providing lift. However, they also observed that the flow
around the butterfly is much more turbulent than expected. This
turbulent flow triggers the complex trajectories characteristic to the
flights of butterflies that may be one of the strategies by which the
insects avoid predators.