Dynamic Analysis of Wave-powered Propulsion Mechanism Based on Global-domain and Local-domain Modes

Wave-powered vehicle play an important role in ocean observation field, among which the underwater propulsion mechanism directly driven by wave energy is the core component of them. Studying the interaction between fluid and rigid body in the flow field is of great significance for improving the propulsion performance of wave-powered vehicle. In this paper, fluid-rigid body coupling dynamic models are established in global-domain and local-domain modes respectively based on the interaction between rigid body dynamics equations and computational fluid dynamics software, and the calculation results of the two modes are compared and analyzed. Firstly, the coupled dynamics was analyzed in the global-domain mode, and fluid grids were established in the entire area by considering forward and heave motion of the underwater propulsion mechanism. Then the hydrodynamic force was substituted into the motion equation of rigid body to obtain its motion parameters, and motion parameters were substituted into the hydrodynamic model for repeated calculations. Considering the disadvantages of large fluid area and large amount of calculation required in the global-domain mode, in the local-domain mode, according to the principle of relative motion, the forward motion of the fin was converted to the same velocity of the reverse flow to act on the fin. A fluid-rigid body coupling model of the fins in a local-domain mode was established, and finite element analysis was realized in a relatively fixed area. In the local-domain mode, the establishment of a finite element mesh in a large area can be avoided, and the calculation efficiency is greatly improved. The calculation results in the two modes are consistent, which provides an effective method for the analysis and research of the propulsion performance of the wave powered propulsion mechanism.