Numerical analysis of an undulating cuttlefish fin for bioinspired propulsion

Bioinspiration offers a powerful approach for designing robotic systems capable of interacting with complex environments by emulating biological strategies. This is particularly relevant in the context of ocean exploration for the conservation of marine ecosystems. A significant portion of marine biodiversity resides near the seabed, an area difficult to explore without disturbing its delicate balance. This work presents a computational fluid dynamics analysis of the lateral fin of cuttlefish, known for its ability to swim with remarkable stability and maneuverability near the seabed. Using an overset mesh approach, a prescribed rigid-body undulatory deformation is imposed on an isolated fin model, without the body mass, resulting in self-propelled forward motion. The resulting wake exhibits complex ring-like vortex structures, shaped by the three-dimensional redistribution of flow around the fin. The impact of wave parameters on swimming performance is assessed, providing an understanding of the mechanisms underlying efficient and environmentally respectful locomotion. Parametric analysis shows that frequency influences swimming speed, while amplitude and wavelength impact on efficiency. Low cost of transport for the isolated fin is achieved at low amplitude and intermediate wavelength. Longer wavelengths increase environmental disturbance, whereas shorter ones help confine the flow, making this propulsion strategy promising for seabed exploration.