Dirichlet-Type Problems for the Two-Dimensional Helmholtz Operator in Complex Quaternionic Analysis

2016 ◽  
Vol 13 (6) ◽  
pp. 4901-4916 ◽  
Author(s):  
Juan Bory-Reyes ◽  
Ricardo Abreu-Blaya ◽  
Luis M. Hernández-Simon ◽  
Baruch Schneider
Keyword(s):  
Quaternionic Analysis ◽  
Two Dimensional ◽  
Helmholtz Operator ◽  
Dirichlet Type

scholarly journals A Numerical Method for SolvingTwo-Dimensional Nonlinear Parabolic ProblemsBased on a Preconditioning Operator

2020 ◽  
Vol 25 (4) ◽  
pp. 531-545
Author(s):  
Amir Hossein Salehi Shayegan ◽  
Ali Zakeri ◽  
Seyed Mohammad Hosseini
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Parabolic Problem ◽  
Time Variable ◽  
Two Dimensional ◽  
Helmholtz Operator ◽  
Mesh Free ◽  
Nonlinear Parabolic ◽  
Spline Finite Element ◽  
Mesh Free Method

This article considers a nonlinear system of elliptic problems, which is obtained by discretizing the time variable of a two-dimensional nonlinear parabolic problem. Since the system consists of ill-conditioned problems, therefore a stabilized, mesh-free method is proposed. The method is based on coupling the preconditioned Sobolev space gradient method and WEB-spline finite element method with Helmholtz operator as a preconditioner. The convergence and error analysis of the method are given. Finally, a numerical example is solved by this preconditioner to show the efficiency and accuracy of the proposed methods.

scholarly journals A computing method for bending problem of thin plate on Pasternak foundation

2020 ◽  
Vol 12 (7) ◽  
pp. 168781402093933
Author(s):  
Jiarong Gan ◽  
Hong Yuan ◽  
Shanqing Li ◽  
Qifeng Peng ◽  
Huanliang Zhang
Keyword(s):  
Boundary Conditions ◽  
Helmholtz Equation ◽  
Integral Equations ◽  
Thin Plate ◽  
Laplace Equation ◽  
Two Dimensional ◽  
Pasternak Foundation ◽  
Helmholtz Operator ◽  
Numerical Computing ◽  
Matlab Programming

The governing equation of the bending problem of simply supported thin plate on Pasternak foundation is degraded into two coupled lower order differential equations using the intermediate variable, which are a Helmholtz equation and a Laplace equation. A new solution of two-dimensional Helmholtz operator is proposed as shown in Appendix 1. The R-function and basic solutions of two-dimensional Helmholtz operator and Laplace operator are used to construct the corresponding quasi-Green function. The quasi-Green’s functions satisfy the homogeneous boundary conditions of the problem. The Helmholtz equation and Laplace equation are transformed into integral equations applying corresponding Green’s formula, the fundamental solution of the operator, and the boundary condition. A new boundary normalization equation is constructed to ensure the continuity of the integral kernels. The integral equations are discretized into the nonhomogeneous linear algebraic equations to proceed with numerical computing. Some numerical examples are given to verify the validity of the proposed method in calculating the problem with simple boundary conditions and polygonal boundary conditions. The required results are obtained through MATLAB programming. The convergence of the method is discussed. The comparison with the analytic solution shows a good agreement, and it demonstrates the feasibility and efficiency of the method in this article.

Use of Shifted Laplacian Operators for Solving Indefinite Helmholtz Equations

2015 ◽  
Vol 8 (1) ◽  
pp. 136-148 ◽  
Author(s):  
Ira Livshits
Keyword(s):  
Hybrid Approach ◽  
Numerical Results ◽  
Laplacian Operator ◽  
Two Dimensional ◽  
Basic Tool ◽  
Helmholtz Equations ◽  
Helmholtz Operator ◽  
Relaxation Properties ◽  
Laplacian Operators ◽  
Complex Damping

AbstractA shifted Laplacian operator is obtained from the Helmholtz operator by adding a complex damping. It serves as a basic tool in the most successful multigrid approach for solving highly indefinite Helmholtz equations — a Shifted Laplacian preconditioner for Krylov-type methods. Such preconditioning significantly accelerates Krylov iterations, much more so than the multigrid based on original Helmholtz equations. In this paper, we compare approximation and relaxation properties of the Helmholtz operator with and without the complex shift, and, based on our observations, propose a new hybrid approach that combines the two. Our analytical conclusions are supported by two-dimensional numerical results.

Vibration of Elastic Structures With Cracks

1993 ◽  
Vol 60 (2) ◽  
pp. 414-421 ◽  
Author(s):  
I. Y. Shen
Keyword(s):  
Integral Equation ◽  
Fredholm Integral Equation ◽  
The Other ◽  
Internal Crack ◽  
Two Dimensional ◽  
Antiplane Strain ◽  
Elastic Solids ◽  
Helmholtz Operator ◽  
Crack Configuration ◽  
Analytical Algorithm

An analytical algorithm is proposed to represent eigensolutions [λm2, ψm(r)]m=1∞ of an imperfect structure C containing cracks in terms of crack configuration σc and eigensolutions [ωn2, φn(r)]n=1∞ of a perfect structured without P the cracks. To illustrate this algorithm on mechanical systems governed by the two-dimensional Helmholtz operator, the Green’s identity and Green’sfunction of P are used to represent ψm(r) in terms of an infinite series of φn(r). Substitution of the ψn(r) representation into the Kamke quotient of C and stationarity of the quotient result in a matrix Fredholm integral equation. The eigensolutions of the Fredholm integral equation then predict λm2 and ψm(r) of C. Finally, eigensolutions of two rectangular elastic solids under antiplane strain vibration, one with a boundary crack and the other with an oblique internal crack, are calculated numerically.

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