准确计算户内变电站大型、复杂的噪声场分布,进而评价可采用降噪措施的减噪效果,是解决户内变电站噪声污染的关键问题。为此,综合声学有限元法(finite element method,FEM)求解复杂声场收敛性好及精度高的优点,及声学边界元法(boundary ...准确计算户内变电站大型、复杂的噪声场分布,进而评价可采用降噪措施的减噪效果,是解决户内变电站噪声污染的关键问题。为此,综合声学有限元法(finite element method,FEM)求解复杂声场收敛性好及精度高的优点,及声学边界元法(boundary element method,BEM)降维求解大型声场的优势,提出了一种基于声学FEM-BEM的户内变电站噪声场求解算法。首先,建立变电站内部声源声固耦合模型,采用声学FEM求解混响噪声作用下的声固耦合响应;然后,基于声学FEM-BEM耦合理论,求解内、外耦合边界处结构单元受声固耦合激励产生的位移及应力载荷;最后,根据声压及应力载荷激发的外场声波扩散模型,基于常规Gauss数值积分法,建立外部空间声域2维BEM声学积分方程,求解外部声场。该算法在湖南某110 kV户内变电站噪声场的求解分析中得到了成功应用,与实测值的相对误差为3.61%~4.87%。展开更多
Sloshing of liquid can increase the dynamic pressure on the storage sidewalls and bottom in tanker ships and LNG careers. Different geometric shapes were suggested for storage tank to minimize the sloshing pressure on...Sloshing of liquid can increase the dynamic pressure on the storage sidewalls and bottom in tanker ships and LNG careers. Different geometric shapes were suggested for storage tank to minimize the sloshing pressure on tank perimeter. In this research, a numerical code was developed to model liquid sloshing in a rectangular partially filled tank. Assuming the fluid to be inviscid, Laplace equation and nonlinear free surface boundary conditions are solved using coupled FEM-BEM. The code performance for sloshing modeling is validated against available data. To minimize the sloshing pressure on tank perimeter, rectangular tanks with specific volumes and different aspect ratios were investigated and the best aspect ratios were suggested. The results showed that the rectangular tank with suggested aspect ratios, not only has a maximum surrounded tank volume to the constant available volume, but also reduces the sloshing pressure efficiently.展开更多
In this study, the magnetohydrodynamic (MHD) flow through a circular pipe under the influence of a transverse mag- netic field when the outside medium is also electrically conducting is solved numerically by using FEM...In this study, the magnetohydrodynamic (MHD) flow through a circular pipe under the influence of a transverse mag- netic field when the outside medium is also electrically conducting is solved numerically by using FEM-BEM coupling approach. The coupled partial differential equations defined for the interior medium are transformed into homogenous modified Helmholtz equations. For the exterior medium on an infinite region, the Laplace equation is considered for the exterior magnetic field. Unknowns in the equations are also related with the corresponding Dirichlet and Neumann type coupled boundary conditions. Unknown values of the magnetic field on the boundary and for the exterior region are obtained by using BEM, and the unknown velocity and magnetic field inside the pipe are obtained by using SUPG type stabilized FEM. Computations are carried for very high values of magnetic Reynolds numbers Rm1, Reynolds number Re and magnetic pressure Rh of the fluid. The results show that using stabilized method enables us to get stable and accurate numerical approximations consistent with the physical configuration of the problem over rough mesh which also results a cheap computational cost.展开更多
In this paper we are concerned with a kind of nonlinear transmission problem with Signorini contact conditions. This problem can be described by a coupled FEM-BEM variational inequality. We first develop a preconditio...In this paper we are concerned with a kind of nonlinear transmission problem with Signorini contact conditions. This problem can be described by a coupled FEM-BEM variational inequality. We first develop a preconditioning gradient projection method for solving the variational inequality. Then we construct an effective domain decomposition preconditioner for the discrete system. The preconditioner makes the coupled inequality problem be decomposed into an equation problem and a "small" inequality problem, which can be solved in parallel. We give a complete analysis to the convergence speed of this iterative method.展开更多
In this paper,we consider a kind of coupled nonlinear problem with Signorini contact conditions.To solve this problem,we discuss a new coupling of finite element and boundary element by adding an auxiliary circle.We f...In this paper,we consider a kind of coupled nonlinear problem with Signorini contact conditions.To solve this problem,we discuss a new coupling of finite element and boundary element by adding an auxiliary circle.We first derive an asymptotic error estimate of the approximation to the coupled FEM-BEM variational inequality.Then we design an iterative method for solving the coupled system,in which only three standard subproblems without involving any boundary integral equation are solved.It will be shown that the convergence speed of this iteration method is independent of the mesh size.展开更多
In this paper we present a coupled Finite Element Method–Boundary Element Method(FEM-BEM)approach for the solution of the free-boundary axi-symmetric plasma equilibrium problem.The proposed method,obtained from an im...In this paper we present a coupled Finite Element Method–Boundary Element Method(FEM-BEM)approach for the solution of the free-boundary axi-symmetric plasma equilibrium problem.The proposed method,obtained from an improvement of the Hagenow-Lackner coupling method,allows to efficiently model the equilibrium problem in unbounded domains by discretizing only the plasma region;the external conductors can be modelled either as 2D or 3D models,according to the problem of interest.The paper explores different iterative methods for the solution of the nonlinear Grad-Shafranov equation,such as Picard,Newton-Raphson and Newton-Krylov,in order to provide a robust and reliable tool,able to handle large-scale problems(e.g.high resolution equilibria).This method has been implemented in the FRIDA code(FReeboundary Integro-Differential Axisimmetric–https://github.om/matteobonotto/FRIDA),together with a suitable Adaptive Integration Technique(AIT)for the computation of the source term.FRIDA has been successfully tested and validated against experimental data from RFX-mod device,and numerical equilibria of an ITER-like device.展开更多
隧道开挖后形成的复杂地质结构导致边坡内部应力场分布极不规则,尤其是近开挖面区域存在强烈的应力集中和近奇异现象,这使得传统的数值模拟方法难以准确捕捉和模拟这些区域的应力状态,进而无法精确预测边坡的变形行为。因此,提出扁平状...隧道开挖后形成的复杂地质结构导致边坡内部应力场分布极不规则,尤其是近开挖面区域存在强烈的应力集中和近奇异现象,这使得传统的数值模拟方法难以准确捕捉和模拟这些区域的应力状态,进而无法精确预测边坡的变形行为。因此,提出扁平状断面高速公路隧道边坡稳定性数值模拟方法。利用边界元法(Boundary Element Method,BEM)求解扁平状断面高速公路隧道边坡内部应力场,克服近奇异问题,确保边界条件的可靠性及初始应力状态的真实性。随后,将BEM数据融入有限元模型(Finite Element Model,FEM),通过精细网格与强大计算力,全面模拟边坡变形过程及其稳定性状态。最后,将FEM的模拟结果作为输入,运用遗传算法(Genetic Algorithm,GA)进行全局搜索,以识别出最危险的滑动面,从而实现对边坡稳定性的精准监测。实验结果表明,上述方法能够有效提升模拟精度,为工程设计加固提供坚实依据。展开更多
This paper introduces a novel hybrid FEM-BEM method for calculating 3D eddy cur-rent field. In the eddy current region, the eddy current density J is solved by the finite element method (FEM) which is discretized by b...This paper introduces a novel hybrid FEM-BEM method for calculating 3D eddy cur-rent field. In the eddy current region, the eddy current density J is solved by the finite element method (FEM) which is discretized by brick finite element mesh, while in the eddy current free re-gion, the magnetic field intensity H is solved by the boundary element method (BEM) which is dis-cretized by rectangular boundary element mesh. Under the boundary conditions, an algebraic equation group is obtained that only includes J by eliminating H. This method has many advan-tages over traditional ones, such as fewer variables, more convenient coupling between the FEM and the BEM and wider application to multiply-connected regions. The calculated values of two models are in good agreement with experimental results. This shows the validity of our method.展开更多
振动污染在国际上已被列入“七大环境公害”之一,填充沟是振动污染治理的一种常用隔振屏障。传统的填充沟受工程造价和施工工艺等限制工程中应用较困难;为克服上述问题,提出一种新型隔振屏障-内插预制芯墙的劲芯水泥土墙。对于饱和地基...振动污染在国际上已被列入“七大环境公害”之一,填充沟是振动污染治理的一种常用隔振屏障。传统的填充沟受工程造价和施工工艺等限制工程中应用较困难;为克服上述问题,提出一种新型隔振屏障-内插预制芯墙的劲芯水泥土墙。对于饱和地基中劲芯水泥土墙的隔振问题,饱和地基采用饱和土半解析边界元法(boundary element method,BEM)建模,劲芯水泥土墙采用有限元法(finite element method,FEM)建模,根据饱和地基-水泥土墙交界面的平衡和连续性条件,分别建立了劲芯水泥土墙对入射Rayleigh波(瑞利波)的远场被动隔振和对动力机器基础振动近场主动隔振的半解析BEM-FEM耦合分析方法,并对劲芯水泥土墙的隔振效果进行了计算分析。研究结果表明:饱和地基中设置劲芯水泥土墙能够起到较好的隔振作用,其隔振效果与混凝土墙基本相当且远优于纯水泥土墙;预制芯墙在劲芯水泥土墙隔振系统中起关键作用,为避免弹性波从芯墙底绕射而降低隔振效果,预制芯墙深度应与水泥土墙深度保持一致;增大芯墙厚度对隔振效果提升不大。在等深芯墙条件下,增大墙深能显著提高远场隔振效果,但对近场隔振效果提升较小;增大墙厚也可提高隔振效果,但提高幅度不大。实际工程中,建议结合工程造价和施工工艺,选择合适的水泥土墙和预制芯墙墙厚。此外,屏障距振源距离对主动隔振效果影响较小,建议根据被保护建筑与振源之间的实际情况,选择合适位置构建隔振屏障。展开更多
变电站噪声存在传播距离远、传播过程中干涉现象明显等特点,导致商业噪声软件的预测值与实测结果常出现不符的情况,使得工程投运后会出现厂界噪声超标现象。为解决此问题,基于有限元-边界元(Finite Element Method-Boundary Element Met...变电站噪声存在传播距离远、传播过程中干涉现象明显等特点,导致商业噪声软件的预测值与实测结果常出现不符的情况,使得工程投运后会出现厂界噪声超标现象。为解决此问题,基于有限元-边界元(Finite Element Method-Boundary Element Method,FEM-BEM)耦合理论,使用有限元仿真软件COMSOL对变压器声源特性及声源等效模型建立方法展开研究。提出一种通过设置双层多线声源的方法建立变压器声源等效模型。通过对声源模型及其传播模型对比实测数据进行研究分析,可发现在距离变压器立面距离5 m之外,仿真噪声衰减数据与实测噪声衰减平均数据的误差基本控制在3 dB以内。本模型可精准预测变电站噪声衰减,为特高压输变电工程的进一步精细化设计提供了理论依据和方法指导。展开更多
文摘准确计算户内变电站大型、复杂的噪声场分布,进而评价可采用降噪措施的减噪效果,是解决户内变电站噪声污染的关键问题。为此,综合声学有限元法(finite element method,FEM)求解复杂声场收敛性好及精度高的优点,及声学边界元法(boundary element method,BEM)降维求解大型声场的优势,提出了一种基于声学FEM-BEM的户内变电站噪声场求解算法。首先,建立变电站内部声源声固耦合模型,采用声学FEM求解混响噪声作用下的声固耦合响应;然后,基于声学FEM-BEM耦合理论,求解内、外耦合边界处结构单元受声固耦合激励产生的位移及应力载荷;最后,根据声压及应力载荷激发的外场声波扩散模型,基于常规Gauss数值积分法,建立外部空间声域2维BEM声学积分方程,求解外部声场。该算法在湖南某110 kV户内变电站噪声场的求解分析中得到了成功应用,与实测值的相对误差为3.61%~4.87%。
文摘Sloshing of liquid can increase the dynamic pressure on the storage sidewalls and bottom in tanker ships and LNG careers. Different geometric shapes were suggested for storage tank to minimize the sloshing pressure on tank perimeter. In this research, a numerical code was developed to model liquid sloshing in a rectangular partially filled tank. Assuming the fluid to be inviscid, Laplace equation and nonlinear free surface boundary conditions are solved using coupled FEM-BEM. The code performance for sloshing modeling is validated against available data. To minimize the sloshing pressure on tank perimeter, rectangular tanks with specific volumes and different aspect ratios were investigated and the best aspect ratios were suggested. The results showed that the rectangular tank with suggested aspect ratios, not only has a maximum surrounded tank volume to the constant available volume, but also reduces the sloshing pressure efficiently.
文摘In this study, the magnetohydrodynamic (MHD) flow through a circular pipe under the influence of a transverse mag- netic field when the outside medium is also electrically conducting is solved numerically by using FEM-BEM coupling approach. The coupled partial differential equations defined for the interior medium are transformed into homogenous modified Helmholtz equations. For the exterior medium on an infinite region, the Laplace equation is considered for the exterior magnetic field. Unknowns in the equations are also related with the corresponding Dirichlet and Neumann type coupled boundary conditions. Unknown values of the magnetic field on the boundary and for the exterior region are obtained by using BEM, and the unknown velocity and magnetic field inside the pipe are obtained by using SUPG type stabilized FEM. Computations are carried for very high values of magnetic Reynolds numbers Rm1, Reynolds number Re and magnetic pressure Rh of the fluid. The results show that using stabilized method enables us to get stable and accurate numerical approximations consistent with the physical configuration of the problem over rough mesh which also results a cheap computational cost.
基金supported by National Natural Science Foundation of China (GrantNo. 10771178)The Key Project of National Natural Science Foundation of China (Grant No. 10531080)+2 种基金National Basic Research Program of China (Grant No. 2005CB321702)supported by The Key Project of National Natural Science Foundation of China (Grant No. 10531080)National Basic Research Program of China (Grant No. 2005CB321701)
文摘In this paper we are concerned with a kind of nonlinear transmission problem with Signorini contact conditions. This problem can be described by a coupled FEM-BEM variational inequality. We first develop a preconditioning gradient projection method for solving the variational inequality. Then we construct an effective domain decomposition preconditioner for the discrete system. The preconditioner makes the coupled inequality problem be decomposed into an equation problem and a "small" inequality problem, which can be solved in parallel. We give a complete analysis to the convergence speed of this iterative method.
基金This work was supported by the National Natural Science Foundation of China, the National PostdoctorFoundation of China, the CAS K. C. Wong Post-doctoral Research Award Fund, the Special Funds for State Major Basic Research (No. 19331023) the State M
文摘In this paper,we consider a kind of coupled nonlinear problem with Signorini contact conditions.To solve this problem,we discuss a new coupling of finite element and boundary element by adding an auxiliary circle.We first derive an asymptotic error estimate of the approximation to the coupled FEM-BEM variational inequality.Then we design an iterative method for solving the coupled system,in which only three standard subproblems without involving any boundary integral equation are solved.It will be shown that the convergence speed of this iteration method is independent of the mesh size.
文摘In this paper we present a coupled Finite Element Method–Boundary Element Method(FEM-BEM)approach for the solution of the free-boundary axi-symmetric plasma equilibrium problem.The proposed method,obtained from an improvement of the Hagenow-Lackner coupling method,allows to efficiently model the equilibrium problem in unbounded domains by discretizing only the plasma region;the external conductors can be modelled either as 2D or 3D models,according to the problem of interest.The paper explores different iterative methods for the solution of the nonlinear Grad-Shafranov equation,such as Picard,Newton-Raphson and Newton-Krylov,in order to provide a robust and reliable tool,able to handle large-scale problems(e.g.high resolution equilibria).This method has been implemented in the FRIDA code(FReeboundary Integro-Differential Axisimmetric–https://github.om/matteobonotto/FRIDA),together with a suitable Adaptive Integration Technique(AIT)for the computation of the source term.FRIDA has been successfully tested and validated against experimental data from RFX-mod device,and numerical equilibria of an ITER-like device.
文摘隧道开挖后形成的复杂地质结构导致边坡内部应力场分布极不规则,尤其是近开挖面区域存在强烈的应力集中和近奇异现象,这使得传统的数值模拟方法难以准确捕捉和模拟这些区域的应力状态,进而无法精确预测边坡的变形行为。因此,提出扁平状断面高速公路隧道边坡稳定性数值模拟方法。利用边界元法(Boundary Element Method,BEM)求解扁平状断面高速公路隧道边坡内部应力场,克服近奇异问题,确保边界条件的可靠性及初始应力状态的真实性。随后,将BEM数据融入有限元模型(Finite Element Model,FEM),通过精细网格与强大计算力,全面模拟边坡变形过程及其稳定性状态。最后,将FEM的模拟结果作为输入,运用遗传算法(Genetic Algorithm,GA)进行全局搜索,以识别出最危险的滑动面,从而实现对边坡稳定性的精准监测。实验结果表明,上述方法能够有效提升模拟精度,为工程设计加固提供坚实依据。
文摘This paper introduces a novel hybrid FEM-BEM method for calculating 3D eddy cur-rent field. In the eddy current region, the eddy current density J is solved by the finite element method (FEM) which is discretized by brick finite element mesh, while in the eddy current free re-gion, the magnetic field intensity H is solved by the boundary element method (BEM) which is dis-cretized by rectangular boundary element mesh. Under the boundary conditions, an algebraic equation group is obtained that only includes J by eliminating H. This method has many advan-tages over traditional ones, such as fewer variables, more convenient coupling between the FEM and the BEM and wider application to multiply-connected regions. The calculated values of two models are in good agreement with experimental results. This shows the validity of our method.
文摘振动污染在国际上已被列入“七大环境公害”之一,填充沟是振动污染治理的一种常用隔振屏障。传统的填充沟受工程造价和施工工艺等限制工程中应用较困难;为克服上述问题,提出一种新型隔振屏障-内插预制芯墙的劲芯水泥土墙。对于饱和地基中劲芯水泥土墙的隔振问题,饱和地基采用饱和土半解析边界元法(boundary element method,BEM)建模,劲芯水泥土墙采用有限元法(finite element method,FEM)建模,根据饱和地基-水泥土墙交界面的平衡和连续性条件,分别建立了劲芯水泥土墙对入射Rayleigh波(瑞利波)的远场被动隔振和对动力机器基础振动近场主动隔振的半解析BEM-FEM耦合分析方法,并对劲芯水泥土墙的隔振效果进行了计算分析。研究结果表明:饱和地基中设置劲芯水泥土墙能够起到较好的隔振作用,其隔振效果与混凝土墙基本相当且远优于纯水泥土墙;预制芯墙在劲芯水泥土墙隔振系统中起关键作用,为避免弹性波从芯墙底绕射而降低隔振效果,预制芯墙深度应与水泥土墙深度保持一致;增大芯墙厚度对隔振效果提升不大。在等深芯墙条件下,增大墙深能显著提高远场隔振效果,但对近场隔振效果提升较小;增大墙厚也可提高隔振效果,但提高幅度不大。实际工程中,建议结合工程造价和施工工艺,选择合适的水泥土墙和预制芯墙墙厚。此外,屏障距振源距离对主动隔振效果影响较小,建议根据被保护建筑与振源之间的实际情况,选择合适位置构建隔振屏障。
文摘变电站噪声存在传播距离远、传播过程中干涉现象明显等特点,导致商业噪声软件的预测值与实测结果常出现不符的情况,使得工程投运后会出现厂界噪声超标现象。为解决此问题,基于有限元-边界元(Finite Element Method-Boundary Element Method,FEM-BEM)耦合理论,使用有限元仿真软件COMSOL对变压器声源特性及声源等效模型建立方法展开研究。提出一种通过设置双层多线声源的方法建立变压器声源等效模型。通过对声源模型及其传播模型对比实测数据进行研究分析,可发现在距离变压器立面距离5 m之外,仿真噪声衰减数据与实测噪声衰减平均数据的误差基本控制在3 dB以内。本模型可精准预测变电站噪声衰减,为特高压输变电工程的进一步精细化设计提供了理论依据和方法指导。
