If you've ever watched Planet Earth, you know the ocean is a wild place to live. The water is full of different ecosystems and organisms varying in complexity from an erudite octopus to a sea star. Unexpectedly, it is the sea star, a simple organism characterized by a decentralized (分散的) nervous system, that offers insights into advanced adaptation to hydrodynamic forces — the forces created by water pressure and flow.
Researchers found that sea stars effectively stay attached to surfaces under extreme hydrodynamic loads by altering their shape. Sea stars create a "downforce" due to their shape. This mean that instead of being lifted by the flow forces, the sea stars are pushed downward toward the rock or floor surface they are on.
"Sea stars are incredibly adaptive," said Luhar, assistant professor. "When there is high wave activity and high water forces, sea stars will grow skinnier and take on a lower profile (姿态). When the sea star is transported to a sheltered environment with lower hydrodynamic forces, they pop up a bit and their cross sections get bigger."
Understanding such shape shifting could help design underwater robots that can similarly adapt to extreme hydrodynamic environments, Luhar said.
The researchers tested this understanding of sea star shape and its impact on force in the water with both computational and 3-D printed models. "Right away what we noticed," Luhar said, "is that instead of the sea stars being pulled away from the surfaces they were on, they were being pushed down- simply because of their shape."
Luhar said the researchers saw this downforce effect as key to how the sea star- and in the future, an underwater robot could stay attched to a sea bed or a rock as opposed to being lifted up away from it, even in the most extreme conditions.
