Turbulent-Reducing Aerofoil Inspired by Owl Feathers

Innovation: Academia

City University London

2020

Image: Pete Nuij / Unsplash / CC BY SA - Creative Commons Attribution + ShareAlike

Move in/Through Gases

Living systems must move through gases (which are less dense than liquids and solids) such as those in the earth’s atmosphere. The greatest challenge of moving in gases is that because the living system is heavier than the gas, it must overcome the force of gravity. Moving efficiently in this light medium presents unique challenges and opportunities for living systems. As a result, they have evolved countless solutions to optimize drag and increase lift so that they can stay aloft and take advantage of variable currents. Additionally, they must overcome gravity when moving from a liquid or solid into the air. The fairyfly, the smallest known insect, is a tiny wasp that must move through the air. To the wasp, air feels like a heavy liquid and to move through it, it uses special feathery oars rather than wings.

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Manage Turbulence

A turbulent force occurs when air or water creates a chaotic or irregular motion. The source can be such things as wind, waves, and eddies caused by obstructions to air or water flow (such as that created by a rock in a stream). Because the force is irregular, it acts in unpredictable ways on multiple parts of a living system at any given time, decreasing the living system’s efficiency. Strategies used to manage turbulence include dampening the amount of turbulence, having flexibility to handle sudden changes, and making quick adjustments. An example is the mucus on aquatic organisms, such as barracuda sharks, that can reduce turbulent friction of seawater by 66%. In doing so, it decreases drag and increases the sharks’ swimming efficiency.

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An aerofoil from City University of London has finlets that stabilize flow and reduce turbulence.

Benefits

Reduced cost
Reduced noise
Increased efficiency

Applications

Aviation
Heating and cooling systems

UN Sustainable Development Goals Addressed

Goal 9: Industry Innovation & Infrastructure
Goal 11: Sustainable Cities & Communities

The Challenge

Energy generation is one of the largest contributors to greenhouse gases, but it’s necessary for many day-to-day operations. Fans and other objects that use airflow to operate require large amounts of energy to be kept constantly running. If these objects were able to run more efficiently, they would use less energy.

Innovation Details

The biomimetic aerofoil mimics the design of owl wings, and has small finlets at the leading edge. Instead of creating vortices, the finlets actually work together as thin guide vanes to keep the air flowing for longer, resulting in greater stability that also reduces turbulence.

Biological Model

Owls are able to approach their prey silently at high speed through management of turbulence. Most of the noise as an object moves through air originates at the trailing edge as air flowing above and below the object meet. This can also increase drag. Many owls have a flexible fringe on the trailing edge of their wing feathers which serves to minimize noise-generating turbulence.

See Related Strategy

Biological Strategy

Wing Feathers Enable Near-Silent Flight

Owl

Specialized feathers of the owl enable near-silent flight by altering air turbulence and absorbing noise.

References

Journal article

Flow turning effect and laminar control by the 3D curvature of leading edge serrations from owl wing

Bioinspiration & Biomimietics

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