| With the rapid development of China‘s economy,the number of super-large structures,including ultra-long water conveyance tunnels and super high-rise buildings,has been increasing year by year.Their structural safety has been paid more and more attention.The finite element method is a very effective tool to analyze the safety of engineering structures.Due to the huge scale of the finite element model of the super-large structure,it is difficult to be processed and solved by using the serial and traditional parallel computing methods.This provides an important practical requirement for the research and development of new parallel computing methods.On the other hand,the rapid development of multicore and multinode supercomputers makes it possible to conduct the mechanics analysis of super-large structures on supercomputers.However,only by the virtue of superior hardware computing power,the high-efficient mechanics analysis of super-large engineering structures cannot be achieved.It is necessary to study parallel computing algorithms which match the topology of modern supercomputers.In this paper,a multisclae parallel numerical simulation method is proposed for the finite element analysis of super-large structures with millions of degrees of freedom;an end-to-end parallel computing method is proposed for the finite element analysis of super-large structures with over ten million degrees of freedom,.Using the "Dawning 5000A" supercomputer at Shanghai Supercomputer Center and "Tianhe 2" supercomputer located in Guangzhou Supercomputer Center,the proposed methods have been applied to the finite element analysis of super-large structures.The main research contents are as follows:The multiscale parallel numerical simulation method for the fininte element analysis of super-large structures is studied.A complete multiscale parallel numerical simulation scheme,including mesh discretization,domain decomposition,and parallel computation,is proposed.The drag-extrusion method and sweep method are used to generate meshes of different scales,and the coupling of meshes with different scales is realized by the fixed-contact and the constraint equations obtained based on the principle of equivalent work.For the two kinds of highly nonlinear mechanics phenomena,namely,structure-structure contact and structure-fluid coupling,the dynamic contact method based on the penalty function,and the fluid-solid coupling method based on the ALE kinematics description and the penalty function method are presented.Furthermore,a coupling load balanced domain decomposition approach are proposed,which can realize the uniform distribution of the coupling elements with high computational load in each partition,so that the real computing load of each partition can be equalized,thereby improving the parallel efficiency and shortening the computing time.An explicit time-doman multiscale solving method is proposed,which can eliminate the effect of elements with different sizes on the steady-solution time step.Combined with the proposed coupling load balanced domain decomposition method,the overall parallel calculation process is presented.The application of multiscale parallel numerical simulation method in practical engineering is carried out.Taking the Qingcaosha ultra-long water conveyance tunnel in Shanghai as the study object,the multiscale finie element simulation model including soil and water body is established by using the multiscale grid discrete and coupling method.Dynamic contact and dynamic fluid-solid coupling are used to simulate the tunnel-soil and tunnel-water interaction,respectively.The dynamic response of the ultra-long water conveyance tunnel under seismic excitation and water hammer impact is analyzed.By comparison with the traditional methods and experimental examples,the reliability of the established multiscale numerical model and the validity of the proposed numerical simulation method are verified.The dynamic responses,such as the stress and deformation,of the tunnel structure under different conditions are analyzed.The influence of different factors on the dynamic response of tunnel structure is discussed,and the parallel efficiency of the multiscale numerical simulation method is analyzed.The end-to-end parallel computing method matching with the modern mainstream multicore and multimode supercomputer for the finite element analysis of super-large structures is studied.A complete set of end-to-end parallel computation algorithms including parallel mesh generation,parallel domain decomposition and parallel system solving is proposed.A hierarchical parallel mesh generation algorithm is proposed.The communication-avoiding mesh multiplication approach based on the global index and update mechanism is adopted to realize the rapid generation of large-scale distributed meshes.The communication among different processes during the mesh multiplication is completely eliminated,and thus,the scalability of near-ideal speedup and parallel efficiency is achieved.A communication-avoiding surface recovery approach based on the overlapping domain decomposition is used to improves the fidelity of the surface mesh to the original geometry model.A hierarchical parallel domain decomposition algorithm is proposed.The data needed for parallel computing is formed by the three-level partitioning of the super-large-scale mesh data based on the multi-layer graph algorithm.The hierarchical domain decomposition takes full account of the hierarchical communication characteristics of modern supercomputers,and thus,adjacent partitions are located within the CPU and the node which both have lower communication costs,greatly reducing the amount of communication needed by the subsequent parallel computation.A hierarchical parallel solving algorithm is proposed.The distributed interface equation is formed by the three-level condensation of sub-regions,and then solved by the parallel preconditioned conjugate gradient method without assembling.The displacement,stress,and strain of each sub-region are obtained through the three-level backward substitution,and the calculation results are output in parallel.The correctness and good scalability of the proposed parallel mesh generation,parallel domain decomposition,and parallel solving algorithms are verified respectively through numerical examples,and the feasibility and reliability of the end-to-end parallel computing method are also verified.The software development and the large-scale engineering application of the end-to-end parallel finite element analysis system are carried out.A high-efficient parallel software development scheme is proposed,in which the core module is completely self-developed,the auxiliary module is realized by open source software,and the overall system architecture is designed.The parallel mesh generation subsystem,the parallel domain decomposition subsystem,and the parallel solving subsystem are developed.And the integration scheme of the whole system is presented.Taking multiple practical engineering models as the application objects,the parallel mesh generation subsystem and the parallel domain decomposition subsystem are used to implement the large-scale grid generation and domain decomposition,and the validity,reliability,and scalability of the subsystems are evaluated.Taking the super high-rise building Shanghai Center Tower as the engineering application object,its end-to-end parallel finite element analysis is performed by using the developed end-to-end parallel finite element analysis software.The parallel performance and correctness of each subsystem are analyzed,and the parallel performance of the whole system is evaluated. |
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