Design and hydrodynamic analysis of a dual-drive bionic robotic fish

Bionic vehicles designed to mimic the structure and swimming behavior of fish offer greater flexibility and higher propulsion efficiency than traditional propeller-driven vehicles. As a result, they have become a research hotspot in the field of ocean exploration. This report presents a design scheme for a bionic robotic fish that integrates caudal and pectoral fin structures. First, the primary structure of the robotic fish was designed, and then three configurations each for the caudal and pectoral fins were developed. A method for calculating the propulsive efficiency of the robotic fish was derived by integrating miles-per-gallon propulsion efficiency metrics into the fluctuating motion equations. Computational fluid dynamics methods with overlapping dynamic mesh techniques were used for numerical simulations to compare the hydrodynamic and swimming performances of different fin structures. This analysis helped tune the configuration to optimize the swimming performance of the robotic fish in two motion states: cruising and climbing. The results indicate that lower motion amplitude and frequency increase propulsive efficiency during cruising. In this state, the tail vortex shedding frequency is twice the motion frequency. During climbing, a 15° deflection angle of the pectoral fins provides the highest lift-to-drag ratio. This study reveals how caudal fin morphology, motion amplitude, and frequency affect swimming efficiency during cruising and how pectoral fin morphology influences performance during climbing. These findings provide valuable insights for future research on the design and motion patterns of bionic robotic fish. •A new bionic robot fish is designed concerning the Carangiform fish.•The design is based on the characteristics of the caudal and pectoral fins.•The swimming efficiency of the fish is related to the structure of the caudal fin and the way of swimming.•The swimming efficiency of the fish is negatively correlated with the propulsive power.•The structure and deflection angle of the pectoral fins greatly affect the climbing process of the fish.