Research On Flow Field Characteristics And Hydrodynamic Of Tandem Double Flapping Wings

In recent years,the exploration and utilization of marine resources has been paid more and more attention all over the world.As an important tool to explore the ocean,underwater navigator is widely used in military and civil fields.However,the turning radius of underwater navigator which use traditional propeller is too large,and the high-speed rotating propeller will reduce the efficiency due to cavitation and cavitation erosion on the surface.Fish swimming in nature has the advantages of rapidity,high efficiency and maneuverability.And the fish by swinging their tails can also reduce the resistance for the individuals in the formation movement.Therefore,the exploration of fish swimming mechanism has always been the research hotspot of fluid mechanics.As a reasonable and simplified model of fish formation swimming,the research of flapping wing in series can provide reference for the development of new efficient propulsion device.According to the motion characteristics of flapping wings,two kinematic models of tandem double flapping wings with pure heave motion and pure pitch motion are established respectively,and the propulsion efficiency evaluation formula under corresponding forms is derived.Based on the overset mesh technology,the numerical simulation of tandem double flapping wings in uniform inflow is carried out.The effectiveness of the numerical calculation model is verified by comparing with references.Then,the numerical simulation of tandem double flapping wings in two motion modes is implemented.The differences of flow field structure and hydrodynamic characteristics between tandem double flapping wings and single flapping wings are studied.The effects of longitudinal spacing,transverse spacing and phase difference on vortex system interference between upstream and downstream flapping wings are analyzed.The differences of flow field structure caused by the changes of these parameters are given.The thrust coefficient time history curve of tandem double flapping wing is studied.Combined with the analysis of flow field structure,the corresponding reasons of hydrodynamic characteristics change are given,and the influence of different layout parameters on propulsion efficiency is obtained.