Thrust characteristic of a caudal fin with spanwise variable phase

•This paper proposes an analysis method to calculate the thrust of fish fin.•To simplify the analysis on the fin, the energy method was proposed.•A flat fin and a waving fin were analyzed and compared using the method.•Real experiments have been conducted to validate the developed method.•From the experiments, we could validate the experimental results.

In this paper, the thrust characteristics of a robotic fish with spanwise variable phase are discussed. To analyze the thrust performance of a robotic fish with spanwise variable phase, an analytical method that uses a simplified method and energy equations is proposed. Experiments were also performed to validate the developed method. The analytical results demonstrate that the thrust characteristic of a caudal fin with spanwise variable phase differs from that of a conventional plate-type caudal fin.