Watching a seabird burst out of the ocean or a mobula ray launch itself into the air makes the transition from water to sky seem effortless.
For drones, however, performing the same maneuver is extremely difficult.
Researchers at the University of Central Florida (UCF) are now studying how to make this challenging transition smoother and more reliable.
Their work could help create a new generation of amphibious drones that can both fly and operate underwater.
The research is being led by Associate Professor of Aerospace Engineering Samik Bhattacharya and aerospace engineering master’s student Dominic Polidoro.
They are investigating what happens when a wing moves out of the water and enters the air, a process scientists call “egress.”
Understanding this process could help improve military amphibious vehicles, but the technology may also have important civilian uses. In the future, amphibious drones could assist with search-and-rescue missions in coastal areas, monitor oceans and marine environments, and support disaster response efforts in flooded regions.
The researchers believe that within the next decade, amphibious drones could become much more capable than today’s versions. Future designs may be able to dive into water and emerge again reliably while carrying heavier equipment and operating autonomously in difficult conditions.
One reason this goal remains challenging is that scientists still do not fully understand what happens when a wing leaves the water.
Previous studies have shown that as a wing rises through the water’s surface, the lifting force it generates suddenly increases. But almost immediately afterward, the lift rapidly drops and even briefly reverses direction before eventually stabilizing. This sudden change can make the vehicle unstable and difficult to control.
For a drone attempting to launch from the water, such abrupt shifts in force could cause it to wobble, lose balance, or fail to take off properly.
According to Bhattacharya, understanding these rapid changes in lift is essential for designing amphibious drones that can either take advantage of these forces or reduce their negative effects.
To investigate the problem, the researchers conduct experiments in UCF’s Experimental Fluid Mechanics Laboratory. They use a water tank and specially designed wings produced with 3D printing technology.
The experiments allow the team to observe several complex physical processes that happen almost simultaneously as a wing exits the water. These include changes in the shape of the water’s surface, the formation of waves, and the shedding of swirling flows known as vortices.
Separating the effects of these different phenomena is extremely difficult because they occur within fractions of a second and strongly influence one another.
By studying these interactions, the researchers hope to build mathematical models that explain exactly how the forces change during egress. These models could then guide the design of future amphibious drones.
Beyond engineering, the research may also improve our understanding of animals that move seamlessly between water and air.
Nature has already solved the problem that engineers are trying to master. By learning from birds and rays, scientists may one day create drones capable of making the same remarkable leap from the water into the sky.
