Owl wing design holds lessons for stealth technology

25 November 2013
By Edd Gent
Mobile version
Share |
Barred Owl hunting in winter (Credit: David Hemmings)

Barred Owl hunting in winter (Credit: David Hemmings)

Understanding owls’ naturally stealthy wing design could help engineers design quieter aircraft, wind turbines and submarines.

Many owl species have developed specialised plumage to effectively eliminate the aerodynamic noise from their wings allowing them to swoop down on prey silently – a feature that could have broad applications for engineers working in fluid dynamics.

A group of researchers from the Lehigh University, USA, lead by Justin Jaworski, assistant professor at the university's Department of Mechanical Engineering and Mechanics are exploring whether owl stealth is based upon a single attribute or the interaction of a combination of attributes.

"Owls possess no fewer than three distinct physical attributes that are thought to contribute to their silent flight capability: a comb of stiff feathers along the leading edge of the wing; a flexible fringe a the trailing edge of the wing; and a soft, downy material distributed on the top of the wing," said Jaworski.

For conventional wings, the sound from the hard trailing edge typically dominates the acoustic signature, but prior theoretical work carried out by Jaworski and Nigel Peake at the University of Cambridge revealed that the porous, compliant character of the owl wing's trailing edge results in significant aerodynamic noise reductions.

"We also predicted that the dominant edge-noise source could be effectively eliminated with properly tuned porous or elastic edge properties, which implies that that the noise signature from the wing can then be dictated by otherwise minor noise mechanisms such as the 'roughness' of the wing surface," said Jaworski.

The velvety down atop an owl's wing creates a compliant but rough surface, much like a soft carpet. This down material may be the least studied of the unique owl noise attributes, but Jaworski believes it may eliminate sound at the source through a novel mechanism that is very different from those of ordinary sound absorbers.

"Our current work predicts the sound resulting from air passing over the downy material, which is idealised as a collection of individual flexible fibres, and how the aerodynamic noise level varies with fiber composition," Jaworski said.

The researchers' results are providing details about how a fuzzy – compliant but rough – surface can be designed to tailor its acoustic signature.

A photographic study of actual owl feathers, carried out with Ian Clark of Virginia Tech, has revealed a surprising 'forest-like' geometry of the down material, so this will be incorporated into the researchers' future theoretical and experimental work to more faithfully replicate the down structure.

Preliminary experiments performed at Virginia Tech show that a simple mesh covering, which replicates the top layer of the 'forest' structure, is effective in eliminating some sound generated by rough surfaces.

"If the noise-reduction mechanism of the owl down can be established, there may be far-reaching implications to the design of novel sound-absorbing liners, the use of flexible roughness to affect trailing-edge noise and vibrations for aircraft and wind turbines, and the mitigation of underwater noise from naval vessels," said Jaworski.

The team is presenting its research at a meeting of the American Physical Society that began yesterday.

Latest Issue

E&T cover image 1606

"Where would Frankenstein and his creative mind fit into today's workplace? Should we fear technological developments or embrace them?"

E&T jobs

  • Graduate Electrical Engineers

    AECOM
    • United Kingdom and Ireland
    • Competitive

    Due to the diverse nature of our business there are many different teams each with very different responsibilities.

    • Recruiter: AECOM

    Apply for this job

  • Network Innovation Engineer / Analyst - UK Power Sector

    Premium job

    Nortech Management Ltd
    • Birmingham, West Midlands or Pershore (Worcestershire)
    • £30,000 - £35,000 (depending on experience) + benefits

    Network Innovation Engineer / Analyst to join a team of talented technology enthusiasts who design and support the low carbon networks of the future.

    • Recruiter: Nortech Management Ltd

    Apply for this job

  • Electrical Engineer with Strong telecoms background

    Premium job

    Sure South Atlantic Ltd
    • Falkland Islands

    Sure South Atlantic Ltd currently has a unique engineering opportunity in their Falkland Islands office. Surrounded by the Atlantic Ocean, teeming ...

    • Recruiter: Sure South Atlantic Ltd

    Apply for this job

  • Cyber, Communication, Information and Data Scientist roles

    Premium job

    Dstl
    • Porton Down, Salisbury
    • Competitive salaries

    Information is everything. Use it to serve your country and help keep us safe.

    • Recruiter: Dstl

    Apply for this job

  • Production Engineer

    Premium job

    Compact Engineering
    • Thirsk / Leeds / Banbury / Colchester / Cambridge
    • Salary will be competitive and commensurate with experience, knowledge, aptitude and capability

    A Production Engineer with some knowledge and understanding of radiant energy transfer.

    • Recruiter: Compact Engineering

    Apply for this job

  • Electronics Engineer

    Premium job

    Nikon Metrology Europe
    • Tring, Hertfordshire

    Nikon Metrology is looking for an Electronics Engineer to join our Electronics Team based in Tring (UK).

    • Recruiter: Nikon Metrology Europe

    Apply for this job

  • Engineering Manager

    BAE Systems
    • Hampshire, England, Portsmouth
    • Competitive package

    Would you like to play a vital role in managing and implementing the correct governance in order to enable BAE Systems to provide assurance and integrity of supply chain data? We currently have a vacancy for an Engineering Manager - Product Integrity

    • Recruiter: BAE Systems

    Apply for this job

  • Engineering Project Manager - Electrical & Automation

    Nestle
    • York, North Yorkshire
    • c£45,000 + Car Allowance + Bonus + Excellent Benefits

    Nestlé Product Technology Centre in York currently has an excellent opportunity for an Engineering Project Manager

    • Recruiter: Nestle

    Apply for this job

  • Consultant Engineer - Test

    BAE Systems
    • Farnborough, Hampshire, England
    • Negotiable

    Consultant Engineer - Test Would you like to be a lead within an exciting team working on one of the UK's largest defence projects? We currently have a vacancy for a Consultant Engineer - Test at our site in Ash Vale. As a Consultant Engineer - Test, you

    • Recruiter: BAE Systems

    Apply for this job

  • ELECTRICAL PROJECT ENGINEER

    SSE
    • Reading, Berkshire
    • SALARY: £37,588 TO £55,669 + CAR (SSE8/9), DEPENDING ON SKILLS AND EXPERIENCE

    SSE are looking to recruit an Electrical Project Engineer into office in Reading

    • Recruiter: SSE

    Apply for this job

More jobs ▶

Subscribe

Choose the way you would like to access the latest news and developments in your field.

Subscribe to E&T