This paper develops and analyzes interior penalty discontinuous Galerkin(IPDG)method by patch reconstruction technique for Helmholtz problems.The technique achieves high order approximation by locally solving a discre...This paper develops and analyzes interior penalty discontinuous Galerkin(IPDG)method by patch reconstruction technique for Helmholtz problems.The technique achieves high order approximation by locally solving a discrete least-squares over a neighboring element patch.We prove a prior error estimates in the L 2 norm and energy norm.For each fixed wave number k,the accuracy and efficiency of the method up to order five with high-order polynomials.Numerical examples are carried out to validate the theoretical results.展开更多
In this paper,we investigate the method of fundamental solutions(MFS)for solving exterior Helmholtz problems with high wave-number in axisymmetric domains.Since the coefficientmatrix in the linear system resulting fro...In this paper,we investigate the method of fundamental solutions(MFS)for solving exterior Helmholtz problems with high wave-number in axisymmetric domains.Since the coefficientmatrix in the linear system resulting fromtheMFS approximation has a block circulant structure,it can be solved by the matrix decomposition algorithm and fast Fourier transform for the fast computation of large-scale problems and meanwhile saving computer memory space.Several numerical examples are provided to demonstrate its applicability and efficacy in two and three dimensional domains.展开更多
In this paper,the boundary knot method is applied to simulate inverse problems of determining physical boundary occurring in an inaccessible interior part.This is fulfilled from measurements of the partially accessibl...In this paper,the boundary knot method is applied to simulate inverse problems of determining physical boundary occurring in an inaccessible interior part.This is fulfilled from measurements of the partially accessible outer boundary.The truncated singular value decomposition under parameter choice of the cross validation method is employed for noisy boundary data cases.Numerical results for two benchmark problems show that the boundary knot method is simple,accurate,stable and computationally efficient for inverse problems under domains with doubly connected domains.展开更多
From the point of view of energy analysis, the cause that the uniqueness of the boundary integral equation induced from the exterior Helmholtz problem does not hold is investigated in this paper. It is proved that the...From the point of view of energy analysis, the cause that the uniqueness of the boundary integral equation induced from the exterior Helmholtz problem does not hold is investigated in this paper. It is proved that the Sommerfeld's condition at the infinity is changed so that it is suitable not only for the radiative wave but also for the absorptive wave when we use the boundary integral equation to describe the exterior Helmholtz problem. There fore, the total energy of the system is conservative. The mathematical dealings to guarantee the uniqueness are discussed based upon this explanation.展开更多
This paper is concerned with the Cauchy problem for the modified Helmholtz equation in an infinite strip domain 0<x≤1,y∈R.The Cauchy data at x = 0 is given and the solution is then sought for the interval 0<x...This paper is concerned with the Cauchy problem for the modified Helmholtz equation in an infinite strip domain 0<x≤1,y∈R.The Cauchy data at x = 0 is given and the solution is then sought for the interval 0<x≤1.This problem is highly ill-posed and the solution(if it exists) does not depend continuously on the given data. In this paper,we propose a fourth-order modified method to solve the Cauchy problem. Convergence estimates are presented under the suitable choices of regularization parameters and the a priori assumption on the bounds of the exact solution.Numerical implementation is considered and the numerical examples show that our proposed method is effective and stable.展开更多
This paper presents a novel wideband fast multipole boundary element approach to 3D half-space/planesymmetric acoustic wave problems.The half-space fundamental solution is employed in the boundary integral equations s...This paper presents a novel wideband fast multipole boundary element approach to 3D half-space/planesymmetric acoustic wave problems.The half-space fundamental solution is employed in the boundary integral equations so that the tree structure required in the fast multipole algorithm is constructed for the boundary elements in the real domain only.Moreover,a set of symmetric relations between the multipole expansion coefficients of the real and image domains are derived,and the half-space fundamental solution is modified for the purpose of applying such relations to avoid calculating,translating and saving the multipole/local expansion coefficients of the image domain.The wideband adaptive multilevel fast multipole algorithm associated with the iterative solver GMRES is employed so that the present method is accurate and efficient for both lowand high-frequency acoustic wave problems.As for exterior acoustic problems,the Burton-Miller method is adopted to tackle the fictitious eigenfrequency problem involved in the conventional boundary integral equation method.Details on the implementation of the present method are described,and numerical examples are given to demonstrate its accuracy and efficiency.展开更多
There are N domains Dj(j=0,1,...,N-1) of different physical parameters in the whole space and their interfaces S,are non-horizontally smooth curved surfaces. The following boundary problem is called Hclinholiz boundar...There are N domains Dj(j=0,1,...,N-1) of different physical parameters in the whole space and their interfaces S,are non-horizontally smooth curved surfaces. The following boundary problem is called Hclinholiz boundary problem:The analytical solution of the above problem is given in this paper.展开更多
We investigate the ultra weak variational formulation(UWVF)of the 2-D Helmholtz equation using a new choice of basis functions.Traditionally the UWVF basis functions are chosen to be plane waves.Here,we instead use fi...We investigate the ultra weak variational formulation(UWVF)of the 2-D Helmholtz equation using a new choice of basis functions.Traditionally the UWVF basis functions are chosen to be plane waves.Here,we instead use first kind Bessel functions.We compare the performance of the two bases.Moreover,we show that it is possible to use coupled plane wave and Bessel bases in the same mesh.As test cases we shall consider propagating plane and evanescent waves in a rectangular domain and a singular 2-D Helmholtz problem in an L-shaped domain.展开更多
We develop a non-overlapping domain decomposition method(DDM)for scalar wave scattering by periodic layered media.Our approach relies on robust boun-dary-integral equation formulations of Robin-to-Robin(RtR)maps throu...We develop a non-overlapping domain decomposition method(DDM)for scalar wave scattering by periodic layered media.Our approach relies on robust boun-dary-integral equation formulations of Robin-to-Robin(RtR)maps throughout the frequency spectrum,including cutoff(or Wood)frequencies.We overcome the obsta-cle of non-convergent quasi-periodic Green functions at these frequencies by incor-porating newly introduced shifted Green functions.Using the latter in the defini-tion of quasi-periodic boundary-integral operators leads to rigorously stable computations of RtR operators.We develop Nystr̈om discretizations of the RtR maps that rely on trigonometric interpolation,singularity resolution,and fast convergent windowed quasi-periodic Green functions.We solve the tridiagonal DDM system via recursive Schur complements and establish rigorously that this procedure is always completed successfully.We present a variety of numerical results concerning Wood frequencies in two and three dimensions as well as large numbers of layers.展开更多
基金the National Key Research and Development Program of China(No.2020YFA0714200)the Science and Technology Major Project of Hubei Province under Grant No.2021AAA010+1 种基金the National Science Foundation of China(Nos.12125103 and 12071362)the Natural Science Foundation of Hubei Province(No.2019CFA007).
文摘This paper develops and analyzes interior penalty discontinuous Galerkin(IPDG)method by patch reconstruction technique for Helmholtz problems.The technique achieves high order approximation by locally solving a discrete least-squares over a neighboring element patch.We prove a prior error estimates in the L 2 norm and energy norm.For each fixed wave number k,the accuracy and efficiency of the method up to order five with high-order polynomials.Numerical examples are carried out to validate the theoretical results.
基金The work described in this paper was supported by National Basic Research Program of China(973 Project No.2010CB832702)the R&D Special Fund for Public Welfare Industry(Hydrodynamics,Project No.201101014 and the 111 project under grant B12032)National Science Funds for Distinguished Young Scholars(Grant No.11125208).The third author acknowledges the support of Distinguished Overseas Visiting Scholar Fellowship provided by the Ministry of Education of China.
文摘In this paper,we investigate the method of fundamental solutions(MFS)for solving exterior Helmholtz problems with high wave-number in axisymmetric domains.Since the coefficientmatrix in the linear system resulting fromtheMFS approximation has a block circulant structure,it can be solved by the matrix decomposition algorithm and fast Fourier transform for the fast computation of large-scale problems and meanwhile saving computer memory space.Several numerical examples are provided to demonstrate its applicability and efficacy in two and three dimensional domains.
基金Supported by the Natural Science Foundation of Anhui Province(1908085QA09)the Natural Science Research Project of Anhui Province(KJ2019A0591&KJ2017B015)Higher Education Department of the Ministry of Education(201802358008)。
文摘In this paper,the boundary knot method is applied to simulate inverse problems of determining physical boundary occurring in an inaccessible interior part.This is fulfilled from measurements of the partially accessible outer boundary.The truncated singular value decomposition under parameter choice of the cross validation method is employed for noisy boundary data cases.Numerical results for two benchmark problems show that the boundary knot method is simple,accurate,stable and computationally efficient for inverse problems under domains with doubly connected domains.
文摘From the point of view of energy analysis, the cause that the uniqueness of the boundary integral equation induced from the exterior Helmholtz problem does not hold is investigated in this paper. It is proved that the Sommerfeld's condition at the infinity is changed so that it is suitable not only for the radiative wave but also for the absorptive wave when we use the boundary integral equation to describe the exterior Helmholtz problem. There fore, the total energy of the system is conservative. The mathematical dealings to guarantee the uniqueness are discussed based upon this explanation.
基金supported by the NSF of China(10571079,10671085)and the program of NCET
文摘This paper is concerned with the Cauchy problem for the modified Helmholtz equation in an infinite strip domain 0<x≤1,y∈R.The Cauchy data at x = 0 is given and the solution is then sought for the interval 0<x≤1.This problem is highly ill-posed and the solution(if it exists) does not depend continuously on the given data. In this paper,we propose a fourth-order modified method to solve the Cauchy problem. Convergence estimates are presented under the suitable choices of regularization parameters and the a priori assumption on the bounds of the exact solution.Numerical implementation is considered and the numerical examples show that our proposed method is effective and stable.
基金supported by the National Natural Science Foundation of China (11172291)the National Science Foundation for Post-doctoral Scientists of China (2012M510162)the Fundamental Research Funds for the Central Universities (KB2090050024)
文摘This paper presents a novel wideband fast multipole boundary element approach to 3D half-space/planesymmetric acoustic wave problems.The half-space fundamental solution is employed in the boundary integral equations so that the tree structure required in the fast multipole algorithm is constructed for the boundary elements in the real domain only.Moreover,a set of symmetric relations between the multipole expansion coefficients of the real and image domains are derived,and the half-space fundamental solution is modified for the purpose of applying such relations to avoid calculating,translating and saving the multipole/local expansion coefficients of the image domain.The wideband adaptive multilevel fast multipole algorithm associated with the iterative solver GMRES is employed so that the present method is accurate and efficient for both lowand high-frequency acoustic wave problems.As for exterior acoustic problems,the Burton-Miller method is adopted to tackle the fictitious eigenfrequency problem involved in the conventional boundary integral equation method.Details on the implementation of the present method are described,and numerical examples are given to demonstrate its accuracy and efficiency.
文摘There are N domains Dj(j=0,1,...,N-1) of different physical parameters in the whole space and their interfaces S,are non-horizontally smooth curved surfaces. The following boundary problem is called Hclinholiz boundary problem:The analytical solution of the above problem is given in this paper.
文摘We investigate the ultra weak variational formulation(UWVF)of the 2-D Helmholtz equation using a new choice of basis functions.Traditionally the UWVF basis functions are chosen to be plane waves.Here,we instead use first kind Bessel functions.We compare the performance of the two bases.Moreover,we show that it is possible to use coupled plane wave and Bessel bases in the same mesh.As test cases we shall consider propagating plane and evanescent waves in a rectangular domain and a singular 2-D Helmholtz problem in an L-shaped domain.
文摘We develop a non-overlapping domain decomposition method(DDM)for scalar wave scattering by periodic layered media.Our approach relies on robust boun-dary-integral equation formulations of Robin-to-Robin(RtR)maps throughout the frequency spectrum,including cutoff(or Wood)frequencies.We overcome the obsta-cle of non-convergent quasi-periodic Green functions at these frequencies by incor-porating newly introduced shifted Green functions.Using the latter in the defini-tion of quasi-periodic boundary-integral operators leads to rigorously stable computations of RtR operators.We develop Nystr̈om discretizations of the RtR maps that rely on trigonometric interpolation,singularity resolution,and fast convergent windowed quasi-periodic Green functions.We solve the tridiagonal DDM system via recursive Schur complements and establish rigorously that this procedure is always completed successfully.We present a variety of numerical results concerning Wood frequencies in two and three dimensions as well as large numbers of layers.
