The Research Of Key Technology In Numerical Simulation Of Biomimetic Fish Based On CFD Software

With billions of years evolution,fishes have developed to remarkable swimming ability.Compared to artificial machines,fish swimming has the characteristics of high efficiency,low energy consumption and high mobility,which has a great enlightenment on the development of underwater robots.Due to the improvement of computer performance and the development of computational methods,numerical simulation plays an increasingly important role in the study of fish swimming.Unlike the experimental method,numerical simulation can specify the shape and swimming mode of fish.What's more,it can be repeated.Based on the CFD software,we can conveniently simulate fish with different shapes or types.Anguilliform swimmers use body/caudal fin(BCF)undulations for propulsion.Rays use undulations of median or pectoral fins(MPF)as their routine propulsive mode.In this paper,the anguilliform swimmers and rays are investigated by different CFD softwares.The major content and innovations of this paper are as follows.This paper analysed the effect of the frequency of the pectoral fins on the swimming performance based on Fluent.We analysed the demand for numerical simulation of biomimetic fish firstly.Then combined with the physical model?numerical method of Fluent,we summarized the simulation process.Three-dimensional mesh with good quality was generated.Analyzing the motion characteristic of rays,the flexible deformation of the fins was designed and implemented based on the dynamic mesh method of Fluent.We analyzed the rays pectoral fin rays swimming performance of the frequency of the wave impact.The influence of the frequency of the pectoral fins on the swimming performance of the rays was analyzed.This paper verified the perception of fish lateral line based on the open-source CFD toolbox OpenFOAM.We analysed the specific needs of anguilliform swimming and pressure perception experiment.The architecture for the numerical simulation of anguilliform swimmers is built.We implemented three key techniques under the framework: mesh generation?pressure sensing and flow velocity estimation.Then the near-body pressure effects of inlet velocity and wave parameters were discussed.We successfully estimated time-varying flow inlets using the near-body pressure.In this paper,an improved changing-topology moving mesh method is developed in OpenFOAM to solve the moving boundary problem.We tested the changing-topology moving mesh algorithm in OpenFOAM,and found two certain problems during the simulation.To address the problems,we propose an improved changing-topology moving mesh method.In order to increase the mesh motion efficiency,a local refinement algorithm is realized to control mesh resolution.An improved checking algorithm is implemented to ensure the regenerated mesh quality is higher than the original mesh.The effectiveness of our method is demonstrated by simulations of the NACA0012 airfoil with translation,rotation and fish-like undulating locomotion.