Abstract: Numerical simulation of the self-propelled fishlike robot is carried out by using computational fluid dynamics. The two robots, which share the same physical model, are undergone with carangiform and thunniform kinematics respectively. Both the energetics and flow structures are extracted for the two modes. Impact factors for improving the swimming performance are summarized by comparison of convergence speed, propulsive force and lateral force, power consumption and propulsive efficiency, flow structures of both modes. The results show that both “undulating tail” and “oscillating tail” play significant roles in fishlike swimming. Comparing with thunniform mode, carangiform mode exhibits a good comprehensive performance. Only within a reasonable parameter range can thunniform mode obtain more excellent performance than carangiform one. As for fishlike robot, an appropriate maximum angle of attack should be selected first and then the phase difference can be adjusted according to the objective of high speed or high efficiency. The findings are of great significance to the understanding of mechanisms of carangiform and thunniform as well as the development of novel fishlike robots.

Key words: Carangiform mode, Energetics, Fishlike robot, Kinematics, Thunniform mode