Dwarf Kingfisher-Inspired Bionic Flapping Wing and Its Aerodynamic Performance at Lowest Flight Speed

Area of Science:

• Aerodynamics
• Bio-inspired engineering
• Fluid mechanics

Background:

• Understanding low-speed flight challenges, particularly lift generation, is crucial for bio-inspired aerial vehicles.
• The dwarf Kingfisher's wing serves as a bionic reference for studying flapping flight dynamics.

Purpose of the Study:

• To numerically investigate and experimentally validate the aerodynamic performance of a Kingfisher-inspired flapping-wing model.
• To examine aerodynamic characteristics at low flight speeds (4.4 m/s) across various wingbeat frequencies and rotation angles.

Main Methods:

• Numerical simulations of the flapping-wing model.
• Experimental validation of simulation results.
• Analysis of aerodynamic coefficients (lift, drag) and flow patterns at different rotation angles (0°-20°) and frequencies (11-21 Hz).

Main Results:

• Increasing wing rotation angle amplifies cycle-averaged lift and drag coefficients.
• Downstroke generates significantly more lift than the upstroke, influenced by rotation angle and wing-wake interaction.
• A stable leading-edge vortex forms during the downstroke and sheds during the upstroke.

Conclusions:

• Passive wing rotation and flexibility are vital for optimizing aerodynamic performance in flapping flight.
• An optimal lift and thrust flapping flight was achieved with a lift coefficient of 3.45 at a 12° rotation angle.