Jet design inspired by silent owl flight

Chiba University researchers have been studying owl flight to design aircraft that emit less noise. They created 3D models of owl wings with special fringes that cut through air while reducing noise. As a result, it could become essential for future airplanes, drones, and flying automobiles.

Follow the latest aircraft trends, and you’ll know that more countries deploy drones for various purposes. Moreover, more companies are introducing flying cars into our cities. However, noise will become a major concern as it is typical for most aircraft. Fortunately, this Chiba research could resolve that issue and bring us a future of safe and silent flying machines.

This article will elaborate on the inspiration behind this low-noise jet design. Later, I will share another cutting-edge aircraft from NASA.

Why base a jet design on owl flight?

Most people know owls as wide-eyed, nocturnal birds that eat rats and smaller animals. However, experts recognize it for its near-soundless flight.

Listen to the video above; you’ll see that an owl can fly past microphones and barely make a sound. On the other hand, you can hear distant drones, helicopters, and planes from the wild whirring of jet turbines and propeller blades. 

These can become too loud for urban populations and animal habitats. The Centers for Disease Control and Prevention (CDC) produce noise levels of up to 140 decibels (dB) during takeoff.

That exceeds 85 dB, which is the level safe for human ears. Consequently, Professor Hao Liu and his Chiba University colleagues studied whether future jet designs could mimic owls. 

Interesting Engineering says multiple research groups attributed their negligible noise to their wings’ micro-fringes, trailing-edge (TE) fringes. The research team started by creating two 3D models of real owl wings. 

One had TE fringes, and the other did not. They used fluid flow simulations, the Ffowcs-Williams-Hawkings equation, and large eddy simulations to assess their performances.

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Tests confirmed that TE fringes reduced the noise from flapping wings while maintaining aerodynamic performance. They decrease airflow fluctuations by breaking up trailing edge vortices. 

They also suppressed the shedding of wingtip vortices by reducing flow interactions between feathers and wingtips. As a result, these mechanisms enhance the effect of TE fringes by improving aerodynamic performance and noise reduction. 

“Our findings demonstrate the effect of complex interactions between the TE fringes and the various wing features, highlighting the validity of using these fringes for reducing noise in practical applications such as drones, wind turbines, propellers, and even flying cars,” Liu said.

Another low-noise jet design from NASA

The National Aeronautics and Space Administration created a jet to return passenger-carrying supersonic aircraft. The X-59 is a joint project between the National Aeronautics and Space Administration and defense tech company Lockheed Martin. 

Its nickname, “Son of Concorde,” comes from its supersonic flight, similar to the Concorde aircraft. It was the first supersonic passenger aircraft that made its first transatlantic flight from London to Bahrain on September 26, 1973.

The original Concorde could take passengers from London to New York in three hours. Unfortunately, airports stopped operations in 2003 due to operating expenses and noise.

The latter came from its sonic boom, the sound it made when it reached supersonic speeds. Concorde enables quick flights by moving faster than the speed of sound.

However, that ability is loud enough to shatter windows! Decades later, the latest NASA jet is the flagship vehicle of the space agency’s Quiet Supersonic Technology or “Quesst” project.

The space agency hopes Quesst would create “sonic thumps” instead of booms. In other words, it should be as loud as slamming a car door from 20 feet away.

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That is quieter than two hands clapping, nearby thunder, or a bouncing basketball. More importantly, the NASA jet can fly at Mach 1.4, 925 mph, or 1,488 kph. Also, it can climb up to 55,000 feet or 16,764 meters.

In contrast, the Son of Concorde is slightly slower than its predecessor. It can reach Mach 2, roughly 1,350 mph or 2,173 kph. Moreover, the original Concorde can reach 60,000 feet or 18,288 meters.

Still, the X-59 could become a more suitable supersonic aircraft due to its Quesst design. The Register says Lockheed Martin’s Skunk Works team transferred it to the flight line for ground checks.

Conclusion

Chiba University researchers studied owl flight to develop a near-silent jet design. Initial tests show adding TE fringes to wings significantly muffles their sound.

The University website says the study deepens our understanding of TE fringes for silent flight. Soon, it could inspire future biomimetic designs that could help develop low-noise fluid machinery.

Learn more about this unique jet design in the Bioinspiration & Biomimetics journal at the IOPScience website. Also, check the latest digital trends at Inquirer Tech.