The effect of the four-tentacled collaboration on the self-propelled performance of squid robot

This study conducts a numerical investigation of the self-propelled performance of a bio-inspired squid robot equipped with four rigid tentacles, exploring three sets of collaborative modes. Leveraging the open-source platform OpenFOAM, we develop a self-propulsion module incorporating the dynamic overset grid technique to manipulate the complex motion of rigid tentacles. The driving system of a single tentacle is simplified into a two-link mechanism, where the phase difference between the links effectively emulates the oscillatory pattern of fish-like locomotion. The interaction of four tentacles gives rise to three distinct driving modes: reverse, homologous, and interlace modes. The results indicate that the homologous mode follows the hydrodynamic characteristics of fish-like waves, the interlace mode can cause the robot to deviate from the initial path, and the reverse mode outperforms the other two modes, exhibiting a higher ultimate cruising speed. Regardless of the propulsion process, the cruising performance of the robot is significantly influenced by the maximum amplitude angle θmax. An increase in θmax also contributes to an elevation in the instantaneous longitudinal force coefficient CFx, with the most pronounced impact observed in the homologous mode. The disparity among the three modes is also evident in the periodic pressure variation and flow field evolution patterns. The vortex distribution during steady-state moments systematically reveals the collaborative effects among the tentacles in different modes on the self-propulsion performance.