Numerical simulations and vorticity dynamics of self-propelled swimming of 3D bionic fish

Numerical simulations and the control of self-propelled swimming of three-dimensional bionic fish in a viscous flow and the mechanism of fish swimming are carried out in this study,with a 3D computational fluid dynamics package,which includes the immersed boundary method and the volume of fluid method,the adaptive multi-grid finite volume method,and the control strategy of fish swimming.Firstly,the mechanism of 3D fish swimming was studied and the vorticity dynamics root was traced to the moving body surface by using the boundary vorticity-flux theory.With the change of swimming speed,the contributions of the fish body and caudal fin to thrust are analyzed quantitatively.The relationship between vortex structures of fish swimming and the forces exerted on the fish body are also given in this paper.Finally,the 3D wake structure of self-propelled swimming of 3D bionic fish is presented.The in-depth analysis of the 3D vortex structure in the role of 3D biomimetic fish swimming is also performed.

Numerical simulations of self-propelled swimming of 3D bionic fish school

Numerical simulations of self-propelled swimming of a three dimensional bionic fish and fish school in a viscous fluid are carried out. This is done with the assistance of a parallel software package produced for 3D moving boundary problems. This computational fluid dynamics package combines the adaptive multi-grid finite volume method, the immersed boundary method and VOF (volume of fluid) method. By using the package results of the self-propelled swimming of a 3D bionic fish and fish school in a vis- cous fluid are obtained. With comparison to the existing experimental measurements of living fishes, the predicted structure of vortical wakes is in good agreement with the measurements.

一种双关节舵机驱动的水质监测仿生机器鱼三维避障方法

为了使仿生机器鱼能在水下安全、高效地完成水质监测任务,采用了一种基于模糊控制实现舵机驱动的机器鱼避障算法,并通过多个红外测距传感器采集的距离得到速度、转角以及上浮下潜3个模糊规则库。最后,利用MATLAB软件搭建了一个由三维空间和多个障碍物构成的模拟场景,并对检测过程进行了模拟,结果表明机器鱼可以成功避障并抵达目的地,从而证明了所提出的三维避障方法的可行性和有效性。

Shape optimization of the caudal fin of the three-dimensional self-propelled swimming fish

Shape optimization of the caudal fin of the three-dimensional self-propelled swimming fish,to increase the swimming efficiency and the swimming speed and control the motion direction more easily,is investigated by combining optimization algorithms,unsteady computational fluid dynamics and dynamic control in this study.The 3D computational fluid dynamics package contains the immersed boundary method,volume of fluid method,the adaptive multi-grid finite volume method and the control strategy of fish swimming.Through shape optimizations of various swimming speeds,the results show that the optimal caudal fins of different swimming modes are not exactly the same shape.However,the optimal fish of high swimming speed,whose caudal fin shape is similar to the crescent,also have higher efficiency and better maneuverability than the other optimal bionic fish at low and moderate swimming speeds.Finally,the mechanisms of vorticity creation of different optimal bionic fish are studied by using boundary vorticity-flux theory,and three-dimensional wake structures of self-propelled swimming of these fish are comparatively analyzed.The study of vortex dynamics reveals the nature of efficient swimming of the 3D bionic fish with the lunate caudal fin.

Topology Optimization of the Caudal Fin of the Three-Dimensional Self-Propelled Swimming Fish

Based on the boundary vorticity-flux theory,topology optimization of the caudal fin of the three-dimensional self-propelled swimming fish is investigated by combining unsteady computational fluid dynamics with moving boundary and topology optimization algorithms in this study.The objective functional of topology optimization is the function of swimming efficiency,swimming speed and motion direction control.The optimal caudal fin,whose topology is different from that of the natural fish caudal fin,make the 3D bionic fish achieve higher swimming efficiency,faster swimming speed and better maneuverability.The boundary vorticity-flux on the body surface of the 3D fish before and after optimization reveals the mechanism of high performance swimming of the topology optimization bionic fish.The comparative analysis between the swimming performance of the 3D topology optimization bionic fish and the 3D lunate tail bionic fish is also carried out,and the wake structures of two types of bionic fish show the physical nature that the swimming performance of the 3D topology optimization bionic fish is significantly better than the 3D lunate tail bionic fish.