Professor Sunghwan Jung, a biologist and environmental engineer, and his student Brian Chang have been studying the fluid dynamics associated with the ‘water entry and exit’ behaviour of aquatic animals, including tiny crustaceans (copepods), frogs and much larger animals. These creatures frequently breach the water using different mechanisms and for various reasons, including hunting, fleeing predators, communicating, saving energy by not swimming and even playing among some animals (such as seals).

“We collected data about aquatic animals of different sizes – from about one millimetre to tens of metres – jumping out of water and were able to reveal how their maximum jumping heights are related to their body size,” said Jung.

When an object – such as a ray – jumps through the water, it acquires some extra mass. This is known as ‘entrained water mass’. This excess water mass is incorporated and swept along in the flow from aquatic animals’ bodies. Jung and Chang found that entrained water mass limits the maximum jumping height of aquatic animals. The researchers hoped that this insight could help shed light on engineering systems which are required to enter and exit water.

The researchers built a very simple, mostly 3D-printed robot which resembled a door hinge to mimic this behaviour. The robot was designed with a rubber band wrapped around the outer perimeter of the hinge and a small wire allowing the hinge to ‘flip’ when water is pushed downward; according to the researchers, this inelegant robot ended up demonstrating the impact of entrained water on breaching behaviour.

While aquatic animals tend to be smooth and streamlined, causing water to slide easily off their bodies and limiting the dampening impact of entrained water mass, most manufactured systems (including the Cornell researchers’ robot) are far less streamlined, causing them to carry more water with them as they ‘leap’ out of the water.

“When we made and tested a robotic system similar to jumping animals, it didn’t jump as much as animals. Why?” asked Jung. “Our robot isn’t as streamlined and carries a lot of water with it. Imagine getting out of a swimming pool with a wet coat – you might not be able to walk due to the water weight.”

Next, the group will work to modify and advance their simple robotic system such that it can leap from the water to the air at similar heights to those reached by aquatic animals like copepods and frogs. “This system might then be able to be used for surveillance near water basins,” Jung suggested.

Professor Sunghwan Jung, a biologist and environmental engineer, and his student Brian Chang have been studying the fluid dynamics associated with the ‘water entry and exit’ behaviour of aquatic animals, including tiny crustaceans (copepods), frogs and much larger animals. These creatures frequently breach the water using different mechanisms and for various reasons, including hunting, fleeing predators, communicating, saving energy by not swimming and even playing among some animals (such as seals).

“We collected data about aquatic animals of different sizes – from about one millimetre to tens of metres – jumping out of water and were able to reveal how their maximum jumping heights are related to their body size,” said Jung.

When an object – such as a ray – jumps through the water, it acquires some extra mass. This is known as ‘entrained water mass’. This excess water mass is incorporated and swept along in the flow from aquatic animals’ bodies. Jung and Chang found that entrained water mass limits the maximum jumping height of aquatic animals. The researchers hoped that this insight could help shed light on engineering systems which are required to enter and exit water.

The researchers built a very simple, mostly 3D-printed robot which resembled a door hinge to mimic this behaviour. The robot was designed with a rubber band wrapped around the outer perimeter of the hinge and a small wire allowing the hinge to ‘flip’ when water is pushed downward; according to the researchers, this inelegant robot ended up demonstrating the impact of entrained water on breaching behaviour.

While aquatic animals tend to be smooth and streamlined, causing water to slide easily off their bodies and limiting the dampening impact of entrained water mass, most manufactured systems (including the Cornell researchers’ robot) are far less streamlined, causing them to carry more water with them as they ‘leap’ out of the water.

“When we made and tested a robotic system similar to jumping animals, it didn’t jump as much as animals. Why?” asked Jung. “Our robot isn’t as streamlined and carries a lot of water with it. Imagine getting out of a swimming pool with a wet coat – you might not be able to walk due to the water weight.”

Next, the group will work to modify and advance their simple robotic system such that it can leap from the water to the air at similar heights to those reached by aquatic animals like copepods and frogs. “This system might then be able to be used for surveillance near water basins,” Jung suggested.