Flight in Ground Effect Dramatically Reduces Aerodynamic Costs in Bats.

Area of Science:

• Aerodynamics
• Bio-inspired engineering
• Animal flight

Background:

• Flying animals frequently fly near surfaces like ground or water.
• This proximity creates an aerodynamic effect, reducing energy expenditure.
• Previous studies predicted significant power savings, but lacked quantitative data.

Purpose of the Study:

• To quantitatively measure the aerodynamic power savings of bats flying in ground effect.
• To compare empirical findings with theoretical predictions.
• To investigate the influence of ground proximity on flight efficiency.

Main Methods:

• Utilized wake-based power measurements to assess aerodynamic power.
• Recorded flight data of Daubenton's bats.
• Analyzed flight kinematics in relation to ground proximity.

Main Results:

• Daubenton's bats exhibited a 29% reduction in aerodynamic power when flying in ground effect.
• Observed savings were double the amount predicted by existing models.
• No variation in savings was found with changing distance above ground within the ground effect zone.

Conclusions:

• Ground effect provides substantial, empirically verified aerodynamic power savings for flying animals.
• Observed savings exceed theoretical predictions, suggesting kinematic adaptations play a key role.
• Ground effect is a widespread phenomenon that likely influenced the evolution of animal flight.