One of Da Vinci's early designs could make modern drones stealthier, scientists say

Independent

6 hours ago

A kind of helicopter design first envisioned by the Renaissance -era Italian polymath Leonardo Da Vinci could help develop quieter and stealthier modern drones, according to a new study.
Drones produce a characteristic high-pitched buzz as their propellers slice through the air. As these remotely operated vehicles become more widely used for package delivery, photography, emergency response and warfare, the noise pollution they produce is only set to increase.
A new study from Johns Hopkins University suggests that a device invented by Leonardo da Vinci more than 500 years ago could hold the key to coming up with quieter drone technology.
Perhaps most famous for his paintings such as the Mona Lisa and The Last Supper, Leonardo was also an engineer and architect, conceptualising plausible flying machines centuries before the age of flight, including a prototype helicopter.
The Leonardo aerial screw, conceived in the 15th century, is one of the earliest known designs for a lift-generating rotor.
Despite this, its aerodynamic and aeroacoustic performance has received limited scientific attention, according to mechanical engineering professor Rajat Mittal, author of the new study.
In the yet-to-be peer-reviewed research, Dr Mittal and his team simulated the aerodynamic forces and sound emissions of a modernised Leonardo aerial screw design.
"Da Vinci's visionary aerial screw – a sort of precursor to the modern helicopter – inspired our investigation," he says.
"The idea was to bring historical inspiration and modern computation together to reimagine a quieter modern drone,' the JHU mechanical engineer said.
The buzzing noises produced by modern drones are due to air vortices around the tip of propellers, which whoosh and intersect with their flat, angled blades.
Researchers theorised that propellers made similar to Leonardo's design, with a screw-like shape and a single blade, can spread those air vortices around and mute the sound.
Scientists ran computer simulations, evaluating the lift, mechanical power, and acoustic emissions from such a design under different air flow conditions.
They compared the results with those from a typical two-bladed rotor that produces similar lift.
Scientists found that the modernised Leonardo design produced less sound intensity for the same lift.
'The aerial screw demonstrates significantly lower mechanical power consumption and acoustic intensity per unit lift,' researchers wrote in the study.
They found that the spiral geometry of the Leonardo aerial screw suppresses interaction between the rotor blade and air vortex and thereby the noise from it.
'The continuous single-blade design of the aerial screw mitigates blade–vortex interaction noise, a key contributor to rotor aeroacoustics,' scientists wrote.
These findings, according to researchers, highlight the potential benefits of unconventional rotor designs for noise-sensitive applications.
'Future work could explore geometrical variations such as increasing the number of turns,' they said.
Scientists hope to further study the structural integrity and stability of the Leonardo design before it is developed into any viable rotorcraft concepts.