The Grace of a Silent Flight - Owl Wings inspire Quieter Aircraft Engines

It’s a bird….it’s a plane….it’s superman!

No….it’s a plane, and a noisy one!

A few years ago, I had moved into my new home and we found out that airplanes pass at a lower altitude over our home as they are about to land. It's very cool to watch it pass right over us......BUT it made us understand how LOUD they can be! When you watch airplanes from a distance, you have to marvel at the intricacies of tech and laws of physics that allow the plane to fly. As it flies over you with it’s rumbling and noisy announcement of arrival, you also realize how noisy and loud Aircraft engines are! This noise is quite noticeable within the cabin of the aircraft as well!

Aircraft engine noise is a significant environmental concern, impacting both human health and wildlife. The loud engine roar disrupts wildlife communication and migration patterns. Airports are often surrounded by noise pollution zones, limiting residential areas and impacting property values.

So what is the primary source of this noise? It is the interaction of the engine's fan blades with the air. As air rapidly moves through the fan, it creates turbulence, resulting in the characteristic roar of an airplane engine.

Nature's Inspiration: The Silent (Stealthy) Hunter – The Owl

Nature has already streamlined ?? this problem! If you notice closely, every bird has a different flying pattern – majorly the flight pattern is similar, but every bird has a unique way to fly based on their functionality and requirements.

BBC Earth showcased the sounds made during flight of different birds, one of which was a barn owl. You can watch the demonstration and notice the difference in sound patterns in the video.

Source: https://www.youtube.com/watch?v=d_FEaFgJyfA

Watch till the end to see the variation in both sound and turbulence during flight!

The silent flight of the owl has long captivated scientists and engineers. Unlike most birds, owls can swoop through the night air with minimal sound, making them stealthy predators. They rely of stealth for hunting and not on speed! This ability comes down to a unique adaptation in their wing feathers.

Owl wings have a serrated leading edge, which is the front part of the wing. These serrations are tiny, sawtooth-like protrusions that disrupt the airflow over the wing. Regular bird feathers create turbulence as air flows over them, generating noise. However, the serrations on owl wings break up the airflow into smaller, less turbulent streams, significantly reducing the sound produced.

Biomimicry in Action: Engineering Quiet with Serrations

SO now, with the inspiration of the Owl’s silent flight, research to develop new winglet designs for airplanes has been in process. These winglet modifications, known as serrated trailing edges (STEs), mimic the owl's wing structure and disrupt the airflow over the wingtips, which are a major source of noise.

The serrations on STEs work by delaying the separation of the airflow over the wing. As air flows over a conventional wing, it tends to detach from the upper surface at a certain point, creating turbulence and noise. The serrations on STEs help the air stay attached longer, resulting in smoother airflow and reduced noise generation.

Extensive wind tunnel testing and flight trials have shown promising results with serrated trailing edges. Studies have demonstrated reductions in aircraft noise significantly. This technology is not just about a quieter cabin experience for passengers. It has the potential to aid in reducing fuel consumption and increasing fuel efficiency.

There are a few challenges associated with the tech, of course. Designing and manufacturing serrated trailing edges requires advanced manufacturing techniques and may initially be more expensive than conventional designs. Additionally, there are concerns about the potential impact of serrations on aerodynamic performance at high speeds.

Researchers are continuously working on optimizing the design and materials used in STEs to address these challenges. Additionally, the integration of STEs with existing airplane designs needs careful consideration to minimize any potential performance drawbacks.

Again, nature has all the solutions!

By learning from nature's ingenious solutions, we can develop innovative technologies that minimize our environmental impact and improve the quality of life for humans and wildlife alike. The future of aviation might be quieter than before, thanks to the silent flight of the owl.

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