The fast solution of linear equations has always been one of the hot spots in scientific computing.A kind of the diagonal matrix splitting iteration methods are provided,which is different from the classical matrix sp...The fast solution of linear equations has always been one of the hot spots in scientific computing.A kind of the diagonal matrix splitting iteration methods are provided,which is different from the classical matrix splitting methods.Taking the decomposition of the diagonal elements for coefficient matrix as the key point,some new preconditioners are constructed.Taking the tri-diagonal coefficient matrix as an example,the convergence domains and optimal relaxation factor of the new method are analyzed theoretically.The presented new iteration methods are applied to solve linear algebraic equations,even 2D and 3D diffusion problems with the fully implicit discretization.The results of numerical experiments are matched with the theoretical analysis,and show that the iteration numbers are reduced greatly.The superiorities of presented iteration methods exceed some classical iteration methods dramatically.展开更多
In this paper,a two-step iteration method is established which can be viewed as a generalization of the existing modulus-based methods for vertical linear complementarity problems given by He and Vong(Appl.Math.Lett.1...In this paper,a two-step iteration method is established which can be viewed as a generalization of the existing modulus-based methods for vertical linear complementarity problems given by He and Vong(Appl.Math.Lett.134:108344,2022).The convergence analysis of the proposed method is established,which can improve the existing results.Numerical examples show that the proposed method is efficient with the two-step technique.展开更多
In this paper,by means of constructing the linear complementarity problems into the corresponding absolute value equation,we raise an iteration method,called as the nonlinear lopsided HSS-like modulus-based matrix spl...In this paper,by means of constructing the linear complementarity problems into the corresponding absolute value equation,we raise an iteration method,called as the nonlinear lopsided HSS-like modulus-based matrix splitting iteration method,for solving the linear complementarity problems whose coefficient matrix in R^(n×n)is large sparse and positive definite.From the convergence analysis,it is appreciable to see that the proposed method will converge to its accurate solution under appropriate conditions.Numerical examples demonstrate that the presented method precede to other methods in practical implementation.展开更多
The mathematical formulation of the mixed-cell-height circuit legalization(MCHCL)problem can be expressed by a linear complementarity problem(LCP)with the system matrix being a block two-by-two saddle point matrix.Bas...The mathematical formulation of the mixed-cell-height circuit legalization(MCHCL)problem can be expressed by a linear complementarity problem(LCP)with the system matrix being a block two-by-two saddle point matrix.Based on the robust modulus-based matrix splitting(RMMS)iteration method and its two-step improvement(RTMMS)studied recently,the well-known Hermitian and skew-Hermitian splitting iteration method and the generalized successive overrelaxation iteration method for solving saddle point linear systems,two variants of robust two-step modulus-based matrix splitting(VRTMMS)iteration methods are proposed for solving the MCHCL problem.Convergence analyses of the proposed two iteration methods are studied in detail.Finally,five test problems are presented.Numerical results show that the proposed two VRTMMS iteration methods not only take full use of the sparse property of the circuit system but also speed up the computational efficiency of the existing RMMS and RTMMS iteration methods for solving the MCHCL problem.展开更多
In this paper,the modulus-based matrix splitting(MMS)iteration method is extended to solve the horizontal quasi-complementarity problem(HQCP),which is characterized by the presence of two system matrices and two nonli...In this paper,the modulus-based matrix splitting(MMS)iteration method is extended to solve the horizontal quasi-complementarity problem(HQCP),which is characterized by the presence of two system matrices and two nonlinear functions.Based on the specific matrix splitting of the system matrices,a series of MMS relaxation iteration methods are presented.Convergence analyses of the MMS iteration method are carefully studied when the system matrices are positive definite matrices and H_(+)-matrices,respectively.Finally,two numerical examples are given to illustrate the efficiency of the proposed MMS iteration methods.展开更多
Adiabatic shear behavior and the corresponding mechanism of TiB2/Al composites were researched by split Hopkinson pressure bar （SHPB）.Results show that the flow stresses of the TiB2/Al composites exhibit softening t...Adiabatic shear behavior and the corresponding mechanism of TiB2/Al composites were researched by split Hopkinson pressure bar （SHPB）.Results show that the flow stresses of the TiB2/Al composites exhibit softening tendency with the increasing of strain rates. All the composites fail in splitting and cutting with a 45 degree, and the phase transformed bands of molten aluminum are found on the adiabatic shear layers. The deformation behavior and shear localization of the TiB2/Al composites specimens were simulated by finite element code MSC.Marc. The Johnson-Cook model was used to describe the thermo-viscoplastic response of the specimen material. There was unanimous between the numerical result and the experimental result on the location of the adiabatic shear band. From the numerical simulation and experiment, it was concluded that the instantaneous failure of the composite was ascribed due to the local low strength area where the formation of adiabatic shear band was, and the stress condition had significant effect on the initiation and propagation of adiabatic shear band （ASB）.展开更多
A quadratic spline collocation method combined with the Crank-Nicolson time discretization of the space fractional diffusion equations gives discrete linear systems,whose coefficient matrix is the sum of a tridiagonal...A quadratic spline collocation method combined with the Crank-Nicolson time discretization of the space fractional diffusion equations gives discrete linear systems,whose coefficient matrix is the sum of a tridiagonal matrix and two diagonalmultiply-Toeplitz-like matrices.By exploiting the Toeplitz-like structure,we split the Toeplitz-like matrix as the sum of a Toeplitz matrix and a rank-2 matrix and Strang’s circulant preconditioner is constructed to accelerate the convergence of Krylov subspace method like generalized minimal residual method for solving the discrete linear systems.In theory,both the invertibility of the proposed preconditioner and the clustering spectrum of the corresponding preconditioned matrix are discussed in detail.Finally,numerical results are given to demonstrate that the performance of the proposed preconditioner is better than that of the generalized T.Chan’s circulant preconditioner proposed recently by Liu et al.(J.Comput.Appl.Math.,360(2019),pp.138–156)for solving the discrete linear systems of one-dimensional and two-dimensional space fractional diffusion equations.展开更多
Kellogg gave a version of the Peaceman-Radford method. In this paper, we introduce a SSOR iteration method which uses Kellogg’s method. The new algorithm has some advantages over the traditional SSOR algorithm. A Cyc...Kellogg gave a version of the Peaceman-Radford method. In this paper, we introduce a SSOR iteration method which uses Kellogg’s method. The new algorithm has some advantages over the traditional SSOR algorithm. A Cyclic Reduction algorithm is introduced via a decoupling in Kellogg’s method.展开更多
A shift splitting concept is introduced and, correspondingly, a shift-splitting iteration scheme and a shift-splitting preconditioner are presented, for solving the large sparse system of linear equations of which the...A shift splitting concept is introduced and, correspondingly, a shift-splitting iteration scheme and a shift-splitting preconditioner are presented, for solving the large sparse system of linear equations of which the coefficient matrix is an ill-conditioned non-Hermitian positive definite matrix. The convergence property of the shift-splitting iteration method and the eigenvalue distribution of the shift-splitting preconditioned matrix are discussed in depth, and the best possible choice of the shift is investigated in detail. Numerical computations show that the shift-splitting preconditioner can induce accurate, robust and effective preconditioned Krylov subspace iteration methods for solving the large sparse non-Hermitian positive definite systems of linear equations.展开更多
A matrix splitting method is presented for minimizing a quadratic programming (QP) problem, and a general algorithm is designed to solve the QP problem and generates a sequence of iterative points. We prove that the s...A matrix splitting method is presented for minimizing a quadratic programming (QP) problem, and a general algorithm is designed to solve the QP problem and generates a sequence of iterative points. We prove that the sequence generated by the algorithm converges to the optimal solution and has an R-linear rate of convergence if the QP problem is strictly convex and nondegenerate, and that every accumulation point of the sequence generated by the general algorithm is a KKT point of the original problem under the hypothesis that the value of the objective function is bounded below on the constrained region, and that the sequence converges to a KKT point if the problem is nondegenerate and the constrained region is bounded.展开更多
We propose the modulus-based cascadic multigrid(MCMG)method and the modulus-based economical cascadic multigrid method for solving the quasi-variational inequalities problem.The modulus-based matrix splitting iterativ...We propose the modulus-based cascadic multigrid(MCMG)method and the modulus-based economical cascadic multigrid method for solving the quasi-variational inequalities problem.The modulus-based matrix splitting iterative method is adopted as a smoother,which can accelerate the convergence of the new methods.We also give the convergence analysis of these methods.Finally,some numerical experiments confirm the theoretical analysis and show that the new methods can achieve high efficiency and lower costs simultaneously.展开更多
In this paper,the backward Euler method and the shifted Grünwald-Letnikov formulas are utilized to discretize the space-fractional diffusion equations.The discretized result is a system of linear equations with a...In this paper,the backward Euler method and the shifted Grünwald-Letnikov formulas are utilized to discretize the space-fractional diffusion equations.The discretized result is a system of linear equations with a coefficient matrix being the sum of a diagonal matrix and a non-Hermitian Toeplitz matrix.By utilizing the Hermitian and skew-Hermitian splitting of the Toeplitz matrix,we develop a two-parameter DThsS iteration method to solve the linear systems.The convergence is also discussed.A DTHsS-t(α,γ)preconditioner is proposed and the preconditioned GMRES method combined with the proposed preconditioner is applied to solve the linear systems.The spectral analysis of the DThsS-τ(α,γ)preconditioned matrix is provided.Experimental results demonstrate the effectiveness of the proposed methods in solving the space-fractional diffusion equations.展开更多
Recently,the projected Jacobi(PJ)and projected Gauss-Seidel(PGS)iteration methods have been studied for solving the horizontal linear complementarity problems(HLCPs).To further improve the convergence rates of the PJ ...Recently,the projected Jacobi(PJ)and projected Gauss-Seidel(PGS)iteration methods have been studied for solving the horizontal linear complementarity problems(HLCPs).To further improve the convergence rates of the PJ and PGS iteration methods,by using the successive overrelaxation(SOR)matrix splitting technique,a projected SOR iteration method is introduced in this paper to solve the HLCP.Convergence analyses are carefully studied when the system matrices are strictly diagonally dominant and irreducibly diagonally dominant.The newly obtained convergence results greatly extend the current convergence theory.Finally,two numerical examples are given to show the effectiveness of the proposed PSOR iteration method and its advantages over the recently proposed PJ and PGS iteration methods.展开更多
A subspace search method for solving quadratic programming with box constraints is presented in this paper. The original problem is divided into many independent subproblem at an initial point, and a search direction ...A subspace search method for solving quadratic programming with box constraints is presented in this paper. The original problem is divided into many independent subproblem at an initial point, and a search direction is obtained by solving each of the subproblem, as well as a new iterative point is determined such that the value of objective function is decreasing. The convergence of the algorithm is proved under certain assumptions, and the numerical results are also given.展开更多
A unified convergence theory is derived for a class of stationary iterative methods for solving linear equality constrained quadratic programs or saddle point problems.This class is constructed from essentially all po...A unified convergence theory is derived for a class of stationary iterative methods for solving linear equality constrained quadratic programs or saddle point problems.This class is constructed from essentially all possible splittings of the submatrix residing in the(1,1)-block of the augmented saddle point matrix that would produce non-expansive iterations.The classic augmented Lagrangian method and alternating direction method of multipliers are two special members of this class.展开更多
A fast compound direct iterative algorithm for solving transient line contact elastohydrodynamic lubrication （EHL） problems is presented. First, by introducing a special matrix splitting iteration method into the tr...A fast compound direct iterative algorithm for solving transient line contact elastohydrodynamic lubrication （EHL） problems is presented. First, by introducing a special matrix splitting iteration method into the traditional compound direct iterative method, the full matrices for the linear systems of equations are transformed into sparse banded ones with any half-bandwidth; then, an extended Thomas method which can solve banded linear systems with any half-bandwidth is derived to accelerate the computing speed. Through the above two steps, the computational complexity of each iteration is reduced approximately from O（N^3/3） to O（β^2N）, where N is the total number of nodes, and β is the half-bandwidth. Two kinds of numerical results of transient EHL line contact problems under sinusoidal excitation or pure normal approach process are obtained. The results demonstrate that the new algorithm increases computing speed several times more than the traditional compound direct iterative method with the same numerical precision. Also the results show that the new algorithm can get the best computing speed and robustness when the ratio, half-bandwidth to total number of nodes, is about 7.5% 10.0% in moderate load cases.展开更多
An efficient and accurate solution algorithm was proposed for 1-D unsteady flow problems widely existing in hydraulic engineering. Based on the split-characteristic finite element method, the numerical model with the ...An efficient and accurate solution algorithm was proposed for 1-D unsteady flow problems widely existing in hydraulic engineering. Based on the split-characteristic finite element method, the numerical model with the Saint-Venant equations of 1-D unsteady flows was established. The assembled f＇mite element equations were solved with the tri-diagonal matrix algorithm. In the semi-implicit and explicit scheme, the critical time step of the method was dependent on the space step and flow velocity, not on the wave celerity. The method was used to eliminate the restriction due to the wave celerity for the computational analysis of unsteady open-channel flows. The model was verified by the experimental data and theoretical solution and also applied to the simulation of the flow in practical river networks. It shows that the numerical method has high efficiency and accuracy and can be used to simulate 1-D steady flows, and unsteady flows with shock waves or flood waves. Compared with other numerical methods, the algorithm of this method is simpler with higher accuracy, less dissipation, higher computation efficiency and less computer storage.展开更多
基金The National Natural Science Foundations of China (12202219)the Natural Science Foundations of Ningxia (2024AAC02009, 2023AAC05001)the Ningxia Youth Top Talents Training Project。
文摘The fast solution of linear equations has always been one of the hot spots in scientific computing.A kind of the diagonal matrix splitting iteration methods are provided,which is different from the classical matrix splitting methods.Taking the decomposition of the diagonal elements for coefficient matrix as the key point,some new preconditioners are constructed.Taking the tri-diagonal coefficient matrix as an example,the convergence domains and optimal relaxation factor of the new method are analyzed theoretically.The presented new iteration methods are applied to solve linear algebraic equations,even 2D and 3D diffusion problems with the fully implicit discretization.The results of numerical experiments are matched with the theoretical analysis,and show that the iteration numbers are reduced greatly.The superiorities of presented iteration methods exceed some classical iteration methods dramatically.
基金supported by the Scientific Computing Research Innovation Team of Guangdong Province(no.2021KCXTD052)the Science and Technology Development Fund,Macao SAR(no.0096/2022/A,0151/2022/A)+3 种基金University of Macao(no.MYRG2020-00035-FST,MYRG2022-00076-FST)the Guangdong Key Construction Discipline Research Capacity Enhancement Project(no.2022ZDJS049)Technology Planning Project of Shaoguan(no.210716094530390)the ScienceFoundation of Shaoguan University(no.SZ2020KJ01).
文摘In this paper,a two-step iteration method is established which can be viewed as a generalization of the existing modulus-based methods for vertical linear complementarity problems given by He and Vong(Appl.Math.Lett.134:108344,2022).The convergence analysis of the proposed method is established,which can improve the existing results.Numerical examples show that the proposed method is efficient with the two-step technique.
基金This work is supported by the National Natural Science Foundation of China with No.11461046the Natural Science Foundation of Jiangxi Province of China with Nos.20181ACB20001 and 20161ACB21005.
文摘In this paper,by means of constructing the linear complementarity problems into the corresponding absolute value equation,we raise an iteration method,called as the nonlinear lopsided HSS-like modulus-based matrix splitting iteration method,for solving the linear complementarity problems whose coefficient matrix in R^(n×n)is large sparse and positive definite.From the convergence analysis,it is appreciable to see that the proposed method will converge to its accurate solution under appropriate conditions.Numerical examples demonstrate that the presented method precede to other methods in practical implementation.
基金National Natural Science Foundation of China(No.11771225)the Qinglan Project of Jiangsu Province and the Science and Technology Project of Nantong City of China(No.JC2021198).
文摘The mathematical formulation of the mixed-cell-height circuit legalization(MCHCL)problem can be expressed by a linear complementarity problem(LCP)with the system matrix being a block two-by-two saddle point matrix.Based on the robust modulus-based matrix splitting(RMMS)iteration method and its two-step improvement(RTMMS)studied recently,the well-known Hermitian and skew-Hermitian splitting iteration method and the generalized successive overrelaxation iteration method for solving saddle point linear systems,two variants of robust two-step modulus-based matrix splitting(VRTMMS)iteration methods are proposed for solving the MCHCL problem.Convergence analyses of the proposed two iteration methods are studied in detail.Finally,five test problems are presented.Numerical results show that the proposed two VRTMMS iteration methods not only take full use of the sparse property of the circuit system but also speed up the computational efficiency of the existing RMMS and RTMMS iteration methods for solving the MCHCL problem.
基金supported by the National Natural Science Foundation of China(No.11771225)the Qinglan Project of Jiangsu Province of Chinathe Science and Technology Project of Nantong City of China(No.JC2021198).
文摘In this paper,the modulus-based matrix splitting(MMS)iteration method is extended to solve the horizontal quasi-complementarity problem(HQCP),which is characterized by the presence of two system matrices and two nonlinear functions.Based on the specific matrix splitting of the system matrices,a series of MMS relaxation iteration methods are presented.Convergence analyses of the MMS iteration method are carefully studied when the system matrices are positive definite matrices and H_(+)-matrices,respectively.Finally,two numerical examples are given to illustrate the efficiency of the proposed MMS iteration methods.
基金the National Engineering Research Center Open Fund(No.2011007B)Natural Science Foundation of GuangDong Province(No.10451064101004631)
文摘Adiabatic shear behavior and the corresponding mechanism of TiB2/Al composites were researched by split Hopkinson pressure bar （SHPB）.Results show that the flow stresses of the TiB2/Al composites exhibit softening tendency with the increasing of strain rates. All the composites fail in splitting and cutting with a 45 degree, and the phase transformed bands of molten aluminum are found on the adiabatic shear layers. The deformation behavior and shear localization of the TiB2/Al composites specimens were simulated by finite element code MSC.Marc. The Johnson-Cook model was used to describe the thermo-viscoplastic response of the specimen material. There was unanimous between the numerical result and the experimental result on the location of the adiabatic shear band. From the numerical simulation and experiment, it was concluded that the instantaneous failure of the composite was ascribed due to the local low strength area where the formation of adiabatic shear band was, and the stress condition had significant effect on the initiation and propagation of adiabatic shear band （ASB）.
基金supported by the research grants MYRG2020-00208-FST from University of Macao2020A1515110454 from Guangdong Basic and Applied Basic Research Foundation+2 种基金2021KCXTD052 from the Scientific Computing Research Innovation Team of Guangdong Provincesupported by the research grant 0118/2018/A3 from Macao Science and Technology Development Fund(FDCT)supported by the research grants MYRG2020-00208-FST and MYRG2022-00262-FST from University of Macao.
文摘A quadratic spline collocation method combined with the Crank-Nicolson time discretization of the space fractional diffusion equations gives discrete linear systems,whose coefficient matrix is the sum of a tridiagonal matrix and two diagonalmultiply-Toeplitz-like matrices.By exploiting the Toeplitz-like structure,we split the Toeplitz-like matrix as the sum of a Toeplitz matrix and a rank-2 matrix and Strang’s circulant preconditioner is constructed to accelerate the convergence of Krylov subspace method like generalized minimal residual method for solving the discrete linear systems.In theory,both the invertibility of the proposed preconditioner and the clustering spectrum of the corresponding preconditioned matrix are discussed in detail.Finally,numerical results are given to demonstrate that the performance of the proposed preconditioner is better than that of the generalized T.Chan’s circulant preconditioner proposed recently by Liu et al.(J.Comput.Appl.Math.,360(2019),pp.138–156)for solving the discrete linear systems of one-dimensional and two-dimensional space fractional diffusion equations.
文摘Kellogg gave a version of the Peaceman-Radford method. In this paper, we introduce a SSOR iteration method which uses Kellogg’s method. The new algorithm has some advantages over the traditional SSOR algorithm. A Cyclic Reduction algorithm is introduced via a decoupling in Kellogg’s method.
基金Research supported by The China NNSF 0utstanding Young Scientist Foundation （No.10525102）, The National Natural Science Foundation （No.10471146）, and The National Basic Research Program （No.2005CB321702）, P.R. China.
文摘A shift splitting concept is introduced and, correspondingly, a shift-splitting iteration scheme and a shift-splitting preconditioner are presented, for solving the large sparse system of linear equations of which the coefficient matrix is an ill-conditioned non-Hermitian positive definite matrix. The convergence property of the shift-splitting iteration method and the eigenvalue distribution of the shift-splitting preconditioned matrix are discussed in depth, and the best possible choice of the shift is investigated in detail. Numerical computations show that the shift-splitting preconditioner can induce accurate, robust and effective preconditioned Krylov subspace iteration methods for solving the large sparse non-Hermitian positive definite systems of linear equations.
基金the National Natural Science Foundation of China (No.19771079)and State Key Laboratory of Scientific and Engineering Computing
文摘A matrix splitting method is presented for minimizing a quadratic programming (QP) problem, and a general algorithm is designed to solve the QP problem and generates a sequence of iterative points. We prove that the sequence generated by the algorithm converges to the optimal solution and has an R-linear rate of convergence if the QP problem is strictly convex and nondegenerate, and that every accumulation point of the sequence generated by the general algorithm is a KKT point of the original problem under the hypothesis that the value of the objective function is bounded below on the constrained region, and that the sequence converges to a KKT point if the problem is nondegenerate and the constrained region is bounded.
基金National Natural Science Foundation of China(12161027)Guangxi Natural Science Foundation,China(2020GXNSFAA159143)Science and Technology Project of Guangxi,China(AD23023002).
文摘We propose the modulus-based cascadic multigrid(MCMG)method and the modulus-based economical cascadic multigrid method for solving the quasi-variational inequalities problem.The modulus-based matrix splitting iterative method is adopted as a smoother,which can accelerate the convergence of the new methods.We also give the convergence analysis of these methods.Finally,some numerical experiments confirm the theoretical analysis and show that the new methods can achieve high efficiency and lower costs simultaneously.
基金the National Natural Science Foundation of China(No.11971215)Science and Technology Project of Gansu Province of China(No.22JR5RA391)+1 种基金Center for Data Science of Lanzhou University,Chinathe Key Laboratory of Applied Mathematics and Complex Systems of Lanzhou University,China.
文摘In this paper,the backward Euler method and the shifted Grünwald-Letnikov formulas are utilized to discretize the space-fractional diffusion equations.The discretized result is a system of linear equations with a coefficient matrix being the sum of a diagonal matrix and a non-Hermitian Toeplitz matrix.By utilizing the Hermitian and skew-Hermitian splitting of the Toeplitz matrix,we develop a two-parameter DThsS iteration method to solve the linear systems.The convergence is also discussed.A DTHsS-t(α,γ)preconditioner is proposed and the preconditioned GMRES method combined with the proposed preconditioner is applied to solve the linear systems.The spectral analysis of the DThsS-τ(α,γ)preconditioned matrix is provided.Experimental results demonstrate the effectiveness of the proposed methods in solving the space-fractional diffusion equations.
基金National Natural Science Foundation of China(No.11771225)Qinglan Project of Jiangsu Province of China.
文摘Recently,the projected Jacobi(PJ)and projected Gauss-Seidel(PGS)iteration methods have been studied for solving the horizontal linear complementarity problems(HLCPs).To further improve the convergence rates of the PJ and PGS iteration methods,by using the successive overrelaxation(SOR)matrix splitting technique,a projected SOR iteration method is introduced in this paper to solve the HLCP.Convergence analyses are carefully studied when the system matrices are strictly diagonally dominant and irreducibly diagonally dominant.The newly obtained convergence results greatly extend the current convergence theory.Finally,two numerical examples are given to show the effectiveness of the proposed PSOR iteration method and its advantages over the recently proposed PJ and PGS iteration methods.
文摘A subspace search method for solving quadratic programming with box constraints is presented in this paper. The original problem is divided into many independent subproblem at an initial point, and a search direction is obtained by solving each of the subproblem, as well as a new iterative point is determined such that the value of objective function is decreasing. The convergence of the algorithm is proved under certain assumptions, and the numerical results are also given.
基金This paper is a polished version of the Rice University technical report CAAMTR10-24which was a work supported in part by the National Natural Science Foundation(No.DMS-0811188)Office of Navy Research(No.N00014-08-1-1101).
文摘A unified convergence theory is derived for a class of stationary iterative methods for solving linear equality constrained quadratic programs or saddle point problems.This class is constructed from essentially all possible splittings of the submatrix residing in the(1,1)-block of the augmented saddle point matrix that would produce non-expansive iterations.The classic augmented Lagrangian method and alternating direction method of multipliers are two special members of this class.
文摘A fast compound direct iterative algorithm for solving transient line contact elastohydrodynamic lubrication （EHL） problems is presented. First, by introducing a special matrix splitting iteration method into the traditional compound direct iterative method, the full matrices for the linear systems of equations are transformed into sparse banded ones with any half-bandwidth; then, an extended Thomas method which can solve banded linear systems with any half-bandwidth is derived to accelerate the computing speed. Through the above two steps, the computational complexity of each iteration is reduced approximately from O（N^3/3） to O（β^2N）, where N is the total number of nodes, and β is the half-bandwidth. Two kinds of numerical results of transient EHL line contact problems under sinusoidal excitation or pure normal approach process are obtained. The results demonstrate that the new algorithm increases computing speed several times more than the traditional compound direct iterative method with the same numerical precision. Also the results show that the new algorithm can get the best computing speed and robustness when the ratio, half-bandwidth to total number of nodes, is about 7.5% 10.0% in moderate load cases.
基金Project supported by the National Nature Science Foundation of China (Grant No.50479068) the Program for New Century Excellent Talents in Universities (Grant No. NCET-04-0494).
文摘An efficient and accurate solution algorithm was proposed for 1-D unsteady flow problems widely existing in hydraulic engineering. Based on the split-characteristic finite element method, the numerical model with the Saint-Venant equations of 1-D unsteady flows was established. The assembled f＇mite element equations were solved with the tri-diagonal matrix algorithm. In the semi-implicit and explicit scheme, the critical time step of the method was dependent on the space step and flow velocity, not on the wave celerity. The method was used to eliminate the restriction due to the wave celerity for the computational analysis of unsteady open-channel flows. The model was verified by the experimental data and theoretical solution and also applied to the simulation of the flow in practical river networks. It shows that the numerical method has high efficiency and accuracy and can be used to simulate 1-D steady flows, and unsteady flows with shock waves or flood waves. Compared with other numerical methods, the algorithm of this method is simpler with higher accuracy, less dissipation, higher computation efficiency and less computer storage.
