Analysis On Hydrodynamic Performance Of Swinging Hydrofoil

With the shortcomings and problems of traditional propulsion methods,biomimetic propulsion,as a new propulsion method,is emerging by observing the characteristics of fish swimming.At present,many researchers at home and abroad have carried out relevant research.In order to improve the propulsion performance and reduce the energy consumption,the geometry and motion characteristics of the underwater biological propulsion device are extracted.Therefore,it is of great significance to study and analyze the propulsion performance of oscillating hydrofoil under different conditions and parameters.In the current research of underwater propulsion,many researchers mainly study the hydrofoil propulsion mode abstracted from fish propulsion.Because of its simple structure,this propulsion mode can be easily used in engineering practice.In the current research,the hydrofoil propulsion mode mainly includes single degree of freedom,two degree of freedom(DOF)and multi degree of freedom,from the angle of efficiency and implementation convenience The best scheme is two degrees of freedom coupling motion.In this paper,the two-DOF motion of rigid hydrofoil is used to investigate its propulsion performance.In order to achieve its optimal propulsion performance,it is necessary to study and analyze the working characteristics and flow field characteristics of the two-degree-of-freedom hydrofoil,which is practical design provides theoretical reference.This article first analyzes the force principle of the swinging hydrofoil,establishes a dynamic model and a kinematics model,sets the movement mode of the fish according to the swimming characteristics of the fish,and sets it to a two-degree-of-freedom coupling with heave and translation movement and rotational movement,and gives a measure of the swing.The definition of hydrofoil propulsion performance parameters,with the help of the overlapping grid technology of STAR CCM+ fluid mechanics software,numerically calculates the influence of the flat swinging hydrofoil airfoil on the propulsion performance under specific working conditions,and calculates the heave motion and rotation motion In the equation,the maximum swing amplitude,maximum swing angle,and motion frequency of the swinging hydrofoil’s propulsion performance are analyzed under specific conditions for the NACA0012 flat-plate hydrofoil’s incoming velocity and its propulsion performance.In addition,the pressure and vorticity distribution of the swinging hydrofoil in the flow field are studied in units of 1/4 cycle.The results of the study show that the increase in the relative thickness of the airfoil has played a role in propelling its propulsion performance;investigation of the impact of swing amplitude and frequency revealed that the maximum swing amplitude is 0.4m,and the average thrust,average thrust coefficient and propulsion of the hydrofoil when the movement frequency is 3Hz The maximum efficiency is obtained;the impact of the swing angle on the propulsion performance is investigated.It is found that the maximum average thrust and the maximum average thrust coefficient appear at the swing angle of 35°,and the maximum propulsion efficiency occurs at the swing angle of 15°;The average thrust and the maximum average thrust coefficient appear at the incoming flow velocity of 3m/s,and the maximum propulsion efficiency occurs at the incoming flow velocity of 5m/s.Secondly,by observing the swinging tail of the relevant fish,changing the span direction of the flat swinging hydrofoil to establish the geometric model of the fork swinging hydrofoil,and analyzing the swept angle,swing amplitude,rotation angle,movement frequency,incoming flow rate Analysis of the influence of hydrofoil propulsion performance.Examining the effect of sweep angle on propulsion performance,it was found that when the sweep angle increases from 50° to 60°,the thrust generated gradually increases,and the thrust generated by the hydrofoil decreases from 60° to 65°.After the angle increased from 65° to 70°,the thrust began to increase again,and the propulsion efficiency continued to decrease with the increase of the sweep angle.Examining the effect of swing amplitude and frequency on the propulsion performance,it was found that the propulsion performance curve was presented by the flat hydrofoil Approximate law;examining the effect of pendulum angle on propulsion performance found that the thrust magnitude and efficiency both decreased;examining the effect of flow velocity on propulsion performance found that the thrust change was very smal,and its propulsion efficiency increased by nearly twice.