Research On Kinematic Mechanism And Hydrodynamic Performance Of Robot Fish

The fish has excellent hydrodynamic performance with high cruising speed, high efficiency and low noise, which is very useful for the research of bionic underwater vehicle. The propulsion and manoeuvre mechanism is used to replace the traditional propulsion system of the underwater vehicle, and it has a great significance to solve such defects as high energy consumption, large noise and low efficiency of current underwater vehicle which has attracted widespread concern in recent years.In this paper, using the advanced fluid analysis technology and powerful post-processing system of Fluent software to study the kinematic mechanism and three-dimensional model of the flow field of robot fish numerically.Firstly, the hydrodynamic performances of tail fin with steady state under the influences of grid system and solution parameters are calculated. And corresponding flow fields are also displayed. By selecting the appropriate calculation model and the method of solving parameters can determine the airfoil.Secondly, the basic theory of fast-start kinematics is studied, fast-start is a transient unsteady swimming, according to the bending shape in the fast-start process of the fish body divided into S-start and C-start and motion equations of S-start and C-start are established. Subsequently, the law of motion of body centerline are simulated and expatiated, and dynamic model are acquired. Based on this, through the simulation and calculation of the robot fish initiative, passive S-start and C-start movement mode, swimming displacement, speed of change and the pressure distribution of flow field, the two fast-start mode movement characteristics and its difference are separately studied.Finally, taking tuna as the bionic object and according to the shape characteristics of tuna, a three-dimensional model of robot fish is established. The mechanics of the fish stressed by the flow field is conducted by using Fluent software. Based on the analysis of the calculation results, the pressure distribution as well as the resistance of the fish body in the specific flow field is presented.The kinematic mechanism and hydrodynamic characteristics of robot fish is studied and analysed based on the theory analysis and simulation calculation integratedly, and the results of simulations are in accordance with the motion law of the fish in nature. The results of this research have also provided the theoretical foundation for the optimal design methods of robot fish.