Vortex wakes generated by robins Erithacus rubecula during free flight in a wind tunnel

Area of Science:

• Aerodynamics
• Bio-inspired engineering
• Fluid dynamics

Background:

• Understanding bird flight aerodynamics is crucial for bio-inspired engineering.
• Previous studies have characterized bird wakes, but individual variations require further investigation.

Purpose of the Study:

• To measure and analyze the aerodynamic wakes of two individual robins.
• To compare wake characteristics with previous studies and assess individual variation.
• To validate models for predicting aerodynamic forces, such as drag, from wake measurements.

Main Methods:

• Digital Particle Image Velocimetry (DPIV) experiments were conducted in a wind tunnel.
• Wake measurements were systematically recorded and analyzed.
• Comparisons were made between individual robins and with historical data.

Main Results:

• No significant individual variation was observed in measured wake quantities.
• Wake structure and its variation with flight speed qualitatively matched previous findings for other bird species.
• A method was developed to account for complex wake structures and estimate vertical momentum flux for weight support.

Conclusions:

• Individual robins exhibit consistent wake characteristics, simplifying aerodynamic analysis.
• The developed procedure effectively accounts for momentum flux and allows drag estimation.
• Simple models can accurately predict major wake structures and other measurable quantities for future bird flight studies.