Numerical Simulation And Experimental Research On Undulatory Propulsion Of Raja Eglanteria

In nature, creatures have experienced the baptism of the nature for thousands of years, eventually evolved to adapt to the environment, has achieved remarkable environmental adaptability in the process. Therefore, the research on biological creature can help to improve the science and technology of human beings. In recent years, the bionic machine in our country’s Marine development and underwater detection have been in big demand, the bionic mechanics gradually become a new research focus in the mechanical discipline. The prototype of bionic robotic fishes imitating different swimming style follow one another in succession at home and abroad, which will bring in revolution of new underwater propulsion technology. The development of bionic robotic fish needs the research on mechanism of fish swimming. To further explore the bionic propulsion mechanism of the prototype, researchers at home and abroad adopt the methods of theoretical analysis and experimental tests, but don’t get comparable result to those of biological fish. Therefore, in order to reveal propulsion mechanism of Raja eglanteria, this paper focus on the research of linear forward swimming and turning problems of bionic rajiform model.This paper proposes a numerical method to investigate the propulsion mechanism of the bionic prototype. Firstly, control equations for the computational domain fluid are established. Secondly, kinematics equations are imposed on the bionic model, which establish the control equations of fish domain. Thirdly, control equations for computational fluid domain and kinematics equations of domain of fish are combined and solved. Since the bionic model deforms initiative in flow field, the movements of model are transferred to the surrounding fluid, which results in a reaction force on the model from surrounding fluid, and then the force drives the model swims forward in the flow field. Finally three-dimensional deformation airfoil is used to test the validity of the numerical method, after argument, the numerical method is applied to do the research of linear forward swimming and turning performance of the bionic model.The proposed numerical method is used to solve the motion process when the bionic rajiform model starts from still and then gradually speeds up convergent to steady state during linear forward swimming.The effects of frequency, wave number and amplitude on the bionic model are respectively analyzed, and the linear forward propulsion performance is discussed under different kinematic parameters. Response Surface Method are applied to further analyze the effect of ki nematic parameters on propulsion performance, and then functions among kinematic parameters, swimming velocity and propulsion efficiency are derived.In some cases, Raja eglanteria need to be able to cope with a variety of contingencies such as sharp turning, food chasing, capture avoiding, etc. Thus, rajiform fish are required to have higher mobility. Thus, the proposed numerical method is also applied to analyze the turning motion of the bionic rajiform model. The effects of undulatory frequency, wave number and amplitude on turning performance are respectively discussed. Response Surface Method are also used to further analyze the effect of kinematic parameters on turning performance under two different turning strategies. Equations among frequency, wave number, amplitude and turning angular velocity are derived when the propagation directions of traveling wave on the bionic model are different. In addition, equations among center frequency, center amplitude, turning radius and turning angular velocity are derived when the propagation directions of traveling wave are the same.A bionic rajiform robotic fish is fabricated in this paper. The mold molding method is used to design the pectoral fins of the robotic fish, and the sequential motions of pectoral fins are utilized to realize the transferring of traveling wave on the robotic fish. Experimental research on linear forward swimming and turning are conducted, excellent linearity is obtained when the robotic fish undulates its pectoral fins symmetrically, good effect of pivot turn are obtained when the robotic fish undulates its pectoral fins asymmetrically. The experimental results are coherent with numerical simulation results, which verify the validity of pectoral fin propulsion mode.