Research On Vortex Street Transition And Hydrodynamic Characteristics Of Flapping Wing

In recent years,the drone industry and the underwater vehicle industry have developed rapidly,and they have been widely used in both the civilian and military fields.However,the unmanned aerial vehicle using propeller propulsion has greater aerodynamic noise,the underwater vehicle adopts the common propeller and rudder combination propulsion method with poor maneuverability.As we all know,birds can achieve high maneuverability and low noise flight by flapping wings,fish can swim freely in a small space by swinging their tail fins.Many scholars have conducted research on bird flapping wing movement and fish swimming,and have proposed a reasonable simplified model,namely flapping wing movement model.In this paper,based on finite volume method and overset mesh technique,numerical simulation of flapping wing motion in uniform steady flow is carried out,and the main research content and results are as follows:Mathematical models of flapping wings were established for two types of motion,and the formulas for calculating the input power of flapping wings applicable to the two types of motion were derived.Based on the existing literature data,the flapping wing coupled with pitch and heave motions is numerically simulated,and the numerical calculation results are compared with the test results to verify the effectiveness of the numerical simulation.Numerical simulation of vortex transition and hydrodynamic characteristics of flapping wing in pure pitch motion was carried out,and the structure of flow field around flapping wing under different pitch motion parameters was given,the influence of the maximum pitch angle and the uniform steady flow Reynolds number on the characteristics of the flow field around the flapping wing of pure pitch motion is analyzed;the time history curve of thrust coefficient of flapping wing in pure pitch motion is given,and the corresponding flapping wing propulsion efficiency is obtained based on the input power calculation formula,Combined with the flow field structure around the flapping wing,the hydrodynamic performance of the flapping wing in pure pitch motion was analyzed.Numerical simulation of the vortex transition and hydrodynamic characteristics of flapping wing in pure heave motion was carried out,and the flow field structure around the flapping wing under different heave motion parameters was given,the influence of heave amplitude and uniform steady flow Reynolds number on the flow field characteristics around flapping wing is analyzed;the thrust coefficient time history curve of flapping wing in pure heave motion is given,and the correspondingflapping wing propulsion efficiency is obtained based on the input power calculation formula,Combined with the flow field structure around the flapping wing,the hydrodynamic performance of the flapping wing in pure heave motion was analyzed.The distribution curves in(CT,CL)parameter space and propulsion efficiency of two types of flapping wing under different motion parameters were compared,and the best motion parameter recognition methods for flapping wing of pure pitch motion and pure heave motion were obtained respectively.