Local mesh refinement is one of the key steps in the implementations of adaptive finite element methods. This paper presents a parallel algorithm for distributed memory parallel computers for adaptive local refinement...Local mesh refinement is one of the key steps in the implementations of adaptive finite element methods. This paper presents a parallel algorithm for distributed memory parallel computers for adaptive local refinement of tetrahedral meshes using bisection. This algorithm is used in PHG, Parallel Hierarchical Grid Chttp：//lsec. cc. ac. cn/phg/）, a toolbox under active development for parallel adaptive finite element solutions of partial differential equations. The algorithm proposed is characterized by allowing simukaneous refinement of submeshes to arbitrary levels before synchronization between submeshes and without the need of a central coordinator process for managing new vertices. Using the concept of canonical refinement, a simple proof of the independence of the resulting mesh on the mesh partitioning is given, which is useful in better understanding the behaviour of the biseetioning refinement procedure.展开更多
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 com...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.展开更多
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 dynami...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.展开更多
基金supported by the 973 Program of China 2005CB321702China NSF 10531080.
文摘Local mesh refinement is one of the key steps in the implementations of adaptive finite element methods. This paper presents a parallel algorithm for distributed memory parallel computers for adaptive local refinement of tetrahedral meshes using bisection. This algorithm is used in PHG, Parallel Hierarchical Grid Chttp：//lsec. cc. ac. cn/phg/）, a toolbox under active development for parallel adaptive finite element solutions of partial differential equations. The algorithm proposed is characterized by allowing simukaneous refinement of submeshes to arbitrary levels before synchronization between submeshes and without the need of a central coordinator process for managing new vertices. Using the concept of canonical refinement, a simple proof of the independence of the resulting mesh on the mesh partitioning is given, which is useful in better understanding the behaviour of the biseetioning refinement procedure.
基金supported by the National Natural Science Foundation of China (Grant No. 10672183)
文摘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.
基金the support of National Natural Science Foundation of China (Grant No.10672183)
文摘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.
