Ground Effect on Undulation and Pumping Near Surfaces.

Area of Science:

• Fluid dynamics
• Biomechanics
• Animal locomotion

Background:

• Locomotion and fluid pumping near surfaces are common in nature.
• Existing studies often focus on isolated systems, lacking a unified framework for boundary interactions.

Purpose of the Study:

• To categorize biological locomotion near surfaces using Undulation number (Un) and Reynolds number (Re).
• To investigate fluid-structure interactions and ground effects in low Re (snails) and high Re (bats, bees) systems.
• To provide a unified framework for understanding biological fluid dynamics near boundaries.

Main Methods:

• Derivation of lubrication models for low Re undulatory propulsion.
• Robotic experiments to validate snail locomotion models.
• Analysis of biological flight data (bats) and fanning behavior (honeybees).
• Examination of ground effect phenomena in different biological systems.

Main Results:

• For snails (low Re, Un > 1), pumping and swimming speeds scale with (a/h0)2, with surface deformation negatively impacting performance.
• For bats and bees (high Re, Un < 1), ground effect significantly enhances lift and facilitates efficient fluid transport (e.g., pheromones).
• Bats exhibit a 2.5-fold increase in lift coefficient near surfaces due to aerodynamic squeezing.

Conclusions:

• A unified framework is established for understanding fluid-structure interactions near boundaries across diverse biological systems.
• The study highlights the distinct mechanisms of locomotion and fluid manipulation employed by organisms at different scales (Re).
• Findings offer insights into the evolutionary adaptations driving efficient biological performance in proximity to surfaces.