Propulsive performance analysis of bionic turtle hydrofoil in coupling movement

Taking the bionic hydrofoil of a hydrofoil propulsion prototype as the research object, a coupling movement method is proposed considering problem of discontinuous thrust generated in stages. Changes of inflow velocity, the angle of attack and the tip trajectory in different coupling motion modes are analyzed. Relationships between motion parameters and average thrust force are compared, when the bio-hydrofoil takes the trigonometric function, triangular and square wave as the profile of stroke spinning angular velocity respectively, and couples with the trigonometric-function-wave-profile azimuth spinning angular velocity. Results of analysis show that in same motion parameters, the coupling movement modes of triangular-wave-profile stroke spinning angular velocity achieves the largest average thrust force. The mode of square-wave-profile stroke spinning angular velocity can obtain the shortest motion period, which improves the largest average thrust force generated by hydrofoil in an indirect way. The ave rage thrust force generate d in the coupling movement mode of trigonometric-function-wave-profile stroke spinning angular velocity is between the other two modes.