Bird gust rejection

Birds make flight in gusty wind conditions look easy, but when we build aircraft at the same scale as birds we find that keeping control in sudden wind gusts is a major challenge. The ability to control your flight and maintain your flight trajectory is especially important when flying at low altitudes close to obstacles.  When we see birds flying on windy days we see the maneouvres they achieve, but we never know the details of the wind flows they are having to cope with.

This project aims to quantify the mechanics of how birds deal with gusts. We have filmed trained falconry birds flying through controlled gusts generated using a bank of fans to measure how their wings move in a gust.  These images were then used to reconstruct the 3D wing shape in high resolution.  This allowed us to use an innovation combination of 3D surface reconstruction, computed tomography (CT) scans, and computational fluid dynamics (CFD) to understand how birds negotiate gusts through wing morphing.

Bird wings act as a suspension system that rejects gusts

In collaborative work with Prof Richard Bomphrey at the Royal Veterinary College, published in Proceedings of the Royal Society B, we have discovered that gliding birds fly smoothly because their wings act as a suspension system. Birds withstand sudden gusts by allowing their wings to pivot about the shoulder absorbing energy and leaving the head and body largely unaffected. The very fastest part of the suspension effect is built into the mechanics of the wings, so birds don’t actively need to do anything. The process is automatic and allows enough time for aerodynamic processes to start to work.

Our next step is to use this new understanding to build better small-scale unmanned aircraft with improved performance in gusts and turbulence.

Lab members

• Jonathan Stevenson

Collaborators

• Prof Richard Bomphrey, Royal Veterinary College

Funding

This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 679355).