Fluid dynamic properties of shark caudal fin morphology and its relationship to habitats

Locomotion is essential for the survival of fish because it influences the success rate of avoiding danger and predation. In particular, differences in the hydrodynamic properties of the caudal fin have a significant impact on swimming, since the caudal fin is the primary propulsion organ. The hydrodynamic characteristics of shark caudal fins have been studied. However, comparisons have been limited to a few species, and more caudal fin morphologies need to be investigated to determine the relationship between caudal fin morphology and hydrodynamic characteristics in sharks with diverse morphologies. Therefore, we performed computational fluid dynamics analysis on the caudal fin morphologies of 30 species in 9 orders of sharks to investigate the relationship between caudal fin morphology and hydrodynamic characteristics. We found that caudal fin morphologies with large ARL (ratio of vertical to the horizontal length of caudal fin) had higher thrust and swimming costs and caudal fin morphologies with small ARS (ratio of the product of the length and height of the caudal fin to the surface area) had higher propulsive efficiency. The results of this study will help in selecting caudal fin morphology for fish-like underwater robots and in studying the relationship between shark ecology and caudal fin morphology.

Automated summary

This study analyzed the caudal fin morphology of 30 species in 9 orders of sharks and found a relationship between caudal fin morphology and hydrodynamic characteristics. Caudal fin morphologies with large ARL had higher thrust and swimming costs, while those with small ARS had higher propulsive efficiency. These findings are important for selecting caudal fin morphology for fish-like underwater robots and studying the relationship between shark ecology and caudal fin morphology.