Engineers have deciphered how the microstructured fins on owl feathers allow them to fly quietly and may show the way to reduce aircraft noise in the future.
A study by Professor Christoph Bruecker of the City University of London describes in the journal Bioinspiration and Biomimetics his translation of detailed three-dimensional geometrical data from typical examples of owl feathers provided by Professor Hermann Wagner at RWTH Aachen University (Germany) into a biomimetic aerodynamic profile to study the aerodynamic effect on the special filaments in the leading edge of the feathers, published by EuropaPress.
The results show that these structures work as sets of fins that consistently rotate the direction of flow near the aerodynamic wall and maintain the flow for longer and with greater stability, avoiding turbulence.
The research team was inspired by the complex three-dimensional geometry of the extensions along the front of the owl’s feathers, reconstructed by Professor Wagner and his team in previous studies using high-resolution micro-CT scanners.
After being transferred to a model in digital form, flow simulations around these structures (using computational fluid dynamics) clearly indicated the aerodynamic function of these extensions as flaps, which rotate the direction of flow in a coherent manner.
This effect is known to stabilize the flow over a sweeping wing aerodynamic profile, typical of owls while flapping and gliding.
Using flow studies in a water tunnel, Professor Bruecker also demonstrated the hypothesis of flow change in experiments with an extended fin model, reports the City University in a statement.
His team was surprised that instead of producing vortices, the fins acted as thin guide fins because of their special 3-D curvature. Therefore, the regular arrangement of such fins over the wingspan changes the direction of flow near the wall in a smooth and consistent manner.
The team plans to use a technical realization of an arrowhead wing profile pattern in an anechoic wind tunnel for further acoustic testing. The result of this research will prove important for future laminar wing design and has the potential to reduce aircraft noise.