Evaluation And Optimization Of Mesh Partitioning Based On OpenFOAM

With the development of numerical methods and computer technologies,computational fluid dynamics(CFD)methods have been widely applied in fields of science and engineering.OpenFOAM is a widely used open-source CFD software.In the simulation of large scale fluid dynamics problems with OpenFOAM on parallel computer systems,one of the key steps is to partition the generated mesh into multiple subdomains and then distribute them to each processor for parallel computing,so as to make full use of parallel system resources and improve execution efficiency.Mesh partitioning is a NP-complete problem,and the partitioning quality can be affected by many factors,therefore it is usually difficult to obtain a theoretically optimal mesh partitioning.In addition,objective functions of existing mesh partitioning methods sometimes can not guarantee an optimal partitioning quality for some practical CFD applications.Based on the above problems,the research content of this thesis is carried out from the following aspects:Firstly,in the part of research background,this thesis introduces the commonly used methods that solve mesh partitioning problems in OpenFOAM,and analyzes the impact of mesh partitioning on parallel CFD simulation performance.In the part of related research status,the thesis summarizes the research status of mesh partitioning,as well as some existing problems in mesh partitioning research,then introduces the mesh partitioning optimization research based on subdomain shape,finally studies the evaluation research on the impact of mesh partitioning on performance.Based on the characteristics of OpenFOAM,the research focuses of this thesis are determined.Secondly,through a large number of experimental analyses,the impact of changing mesh partitioning factors on mesh partitioning quality and CFD simulation performance is evaluated based on OpenFOAM.The mesh partitioning factors here include processor face number,subdomain AR(Aspect Ratio),load,partitioning direction,mapping and so on.A series of rules are designed to make various and numerous mesh partitioning changes based on commonly used mesh partitioning methods in OpenFOAM.Through the experimental analyses of two representative cases in OpenFOAM,some specific guidelines for mesh partitioning are showed.Then,an AR based mesh partitioning optimization method ARMetis is designed in view of the limitation of objective functions of Metis method in OpenFOAM.The thesis first studies the optimization objectives and corresponding implementation methods of Metis method,and then solves four basic issues that need to be considered in the design of ARMetis,including the definition of AR,the calculation of AR,the storage of additional information for AR and the data structure of ARMetis.On these bases,the basic idea and overall framework of ARMetis are proposed,and the design of two key modules of this method is introduced.Finally,this thesis implements and verifies the ARMetis method.Based on OpenFOAM and multi-level k-way partitioning algorithm,this thesis implements each module of the method according to the overall framework of ARMetis.The implementation algorithms are showed here.At last this thesis chooses some practical cases to verify the ARMetis method.