Fluid-structure interaction modeling on a 3D ray-strengthened caudal fin

Area of Science:

• Fluid dynamics
• Biomechanics
• Computational modeling

Background:

• Fish fin locomotion is crucial for aquatic movement.
• Understanding the role of skeletal structures in fin dynamics is key.
• Existing models often simplify the complex fluid-structure interactions.

Purpose of the Study:

• To develop and validate a numerical model for skeleton-reinforced fish fin dynamics.
• To investigate the impact of varying ray stiffness distributions on fin deformation and propulsion.
• To identify optimal stiffness patterns for enhanced swimming performance.

Main Methods:

• Solving Navier-Stokes equations using a finite-volume method on an overset, multi-block structured grid.
• Modeling fin bony rays as nonlinear Euler-Bernoulli beams.
• Simulating fluid-structure interaction in a 3D caudal fin model with different stiffness distributions.

Main Results:

• The model successfully reproduces fish-like fin deformations, such as cupping, through passive structural responses.
• Cupping stiffness distribution minimizes power expenditure.
• Uniform stiffness distribution maximizes thrust generation and propulsive efficiency.
• Uniform stiffness also induces cupping deformations with reduced inter-ray phase differences.

Conclusions:

• Numerical modeling of fluid-structure interaction is effective for studying fish fin biomechanics.
• Ray stiffness distribution significantly influences fin deformation, power consumption, thrust, and efficiency.
• The uniform stiffness distribution offers a promising strategy for optimizing fin propulsion.