Flow over a traveling wavy foil with a passively flapping flat plate

Area of Science:

• Fluid dynamics
• Biomimetics
• Animal locomotion

Background:

• Understanding fish swimming mechanics is crucial for biomimetic design.
• The caudal fin's role in generating thrust is significant but complex.
• Modeling fluid-structure interaction in aquatic locomotion is challenging.

Purpose of the Study:

• To investigate the influence of fish caudal fin flexibility on swimming performance.
• To analyze the propulsive force generated by a wavy foil with a passively flapping plate.
• To model the effect of fin flexibility on the overall locomotion of swimming animals.

Main Methods:

• Utilized a multiblock lattice Boltzmann equation for fluid flow simulation.
• Employed the immersed boundary method to model fluid-structure interaction.
• Represented caudal fin flexibility using a torsion spring model.

Main Results:

• The passively flapping plate contributed approximately 50% of the total propulsive force.
• Caudal fin flexibility (nondimensional natural frequency F) significantly impacts movement and thrust.
• Excessive flexibility leads to drag; increased rigidity enhances thrust, especially with localized undulation.

Conclusions:

• Caudal fin flexibility is a critical factor in efficient aquatic locomotion.
• The simplified model accurately reflects key aspects of natural swimming behaviors.
• Optimal fin rigidity is necessary for maximizing propulsive force and achieving steady movement.