Hydrodynamic Characteristics Analysis Of Pectoral Caudal Synergy Propulsion Bionic Robot Fish Based On CFD

With the development of research and application of underwater robots,then the efficiency and performance of bionic robotic fish need to be improved so that they can be adapted to longer and more complex tasks.It is well known that the accurate simulation of the dynamic behavior of bionic robot fish and the design of high performance motion attitude controller depend on the accurate hydrodynamic model of carrier and propulsion system.Therefore,it is very important to study the fluid dynamics of robotic fish by establishing an accurate hydrodynamic model and simulating its swimming mode by modal simulation analysis software.In this paper,the Computational Fluid Dynamics(CFD)technology was used to study the hydrodynamics effects of the thoracic and caudal fin coordinated propulsion of the robotic fish under different motion conditions.The main work and innovative results are as follows:(1)The whole robot fish was put into the flow field,and the pectoral fins and caudal fins on both sides moved in a sinusoidal pattern.A sliding grid model of the bionic robot fish was established,and CFD fluid simulation software was used,and the whole fish on the straight trip pectoral fin propulsion mode,caudal fin propulsion mode and pectoral fin coordinated propulsion mode were compared,and the hydrodynamic characteristics of the robotic fish were obtained under different dynamic modes.From the pressure change cloud diagram,the pressure change caused by pectoral-caudal fin propulsion is the most complicated.From the velocity vorticity variation diagram,the co-propulsion of the pectoral and caudal fins produces the most complicated vorticity change.The vortexes generated by pectoral fin movement will gradually fall back and interact with the vortexes generated by the caudal fin to increase the thrust of the caudal fin,which proves that the pectoral and caudal fin coordinated propulsion mode is an efficient propulsion mechanism.(2)By using the sliding and moving mesh model of direct swimming of robotic fish and CFD fluid simulation software,the hydrodynamic characteristics of the robot fish under the coordination of the coupled motion of pectoral fin and front and rear flap and the single degree of freedom motion of caudal fin to propel the direct swimming attitude were studied.Concluded to make pectoral fins to produce better propulsive effect,the phase difference between pectoral fin and caudal fin should be set as the value of90°,the phase difference between pectoral fin rocker and pat wing should be set as the value of60°,pectoral fins at1Hz frequency,frequency of tail fin at 1.5Hz,pectoral fins taken wing amplitude is60°,pectoral fins wave wing amplitude and tail fin flapping amplitude is90°.(3)A sliding moving grid model of the bionic robot fish turning motion was established,and the hydrodynamic characteristics of the bionic robot fish under the coordinated propulsion of the pectoral and caudal fins were analyzed by using CFD fluid simulation software.From the simulation analysis,it is concluded that the parameters that enable the thoracic and caudal fins to promote together can produce a better turning propulsion effect are,the phase difference between the thoracic and caudal fins is30°,the phase difference between pectoral fin rocker and pat wing is60°,pectoral fin frequency is set at 2Hz,caudal fin frequency is set at 1Hz,pectoral fin amplitude is60°,pectoral fin flapping amplitude is90°,caudal fin flapping amplitude is70°.