Computational fluid dynamics (CFD) is used extensively by engineers to model and analyze complex issues related to hydraulic design, planning studies for future generating stations, civil maintenance and supply effici...
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Computational fluid dynamics (CFD) is used extensively by engineers to model and analyze complex issues related to hydraulic design, planning studies for future generating stations, civil maintenance and supply efficiency. In order to find the optimal position of a baffle in a rectangular primary sedimentation tank, computational investigations are performed. Also laboratory experiments are conducted to verify the numerical results and the measured velocity fields which were by Acoustic Doppler Velocimeter (ADV) are used. The gmres algorithm as a pressure solver was used in the computational modeling. The results of computational investigations performed in the present study indicate that the favorable flow field (uniform in the settling zone) would be enhanced for the case that the baffle position provide small circulation regions volume and dissipate the kinetic energy in the tank. Also results show that the gmres algorithm can obtain the good agreement between the results of numerical models and experimental tests. (C) 2012 Elsevier Inc. All rights reserved.
Purpose - This paper compares the hybrid FEM-BEM and FEM-DBCI methods for the solution of open-boundary static and quasi-static electromagnetic field problems. Design/methodology/approach - After a brief review of the...
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Purpose - This paper compares the hybrid FEM-BEM and FEM-DBCI methods for the solution of open-boundary static and quasi-static electromagnetic field problems.
Design/methodology/approach - After a brief review of the two methods (both coupling a differential equation for the interior problem with an integral equation for the exterior one), they are compared in terms of accuracy, memory and computing time requirements by means of a set of simple examples.
Findings - The comparison suggests that FEM-BEM is more accurate than FEM-DBCI but requires more computing time.
Practical implications - Then FEM-DBCI appears more appropriate for applications which require a shorter computing time, for example in the stochastic optimization of electromagnetic devices. Conversely, FEM-BEM is more appropriate in cases in which a high level of precision is required in a single computation.
Originality/value - Note that the FEM-BEM considered in this paper is a non standard one in which the nodes of the normal derivative on the truncation boundary are placed in positions different from those of the potential.
This paper describes a new algorithm to solve the neutron transport stationary equation in 2-D geometry. This algorithm is based on a splitting of the collision operator and an infinite dimensional adaptation of the G...
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This paper describes a new algorithm to solve the neutron transport stationary equation in 2-D geometry. This algorithm is based on a splitting of the collision operator and an infinite dimensional adaptation of the gmres method accelerated by a symmetric Gauss-Seidel preconditioning. The theoretical proof of the convergence and the numerical results are given in this work.
The matrix-free Newton-Krylov method that uses the gmres algorithm (an iterative algorithm for solving systems of linear algebraic equations) is used for the parametric continuation of the solitary traveling pulse sol...
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The matrix-free Newton-Krylov method that uses the gmres algorithm (an iterative algorithm for solving systems of linear algebraic equations) is used for the parametric continuation of the solitary traveling pulse solution in a three-component reaction-diffusion system. Using the results of integration on a short time interval, we replace the original system of nonlinear algebraic equations by another system that has more convenient (from the viewpoint of the spectral properties of the gmres algorithm) Jacobi matrix. The proposed parametric continuation proved to be efficient for large-scale problems, and it made it possible to thoroughly examine the dependence of localized solutions on a parameter of the model.
We propose a method of Lanczos type for solving a linear system with a normal matrix whose spectrum is contained in a second-degree curve. This is a broader class of matrices than that of the (l, m)-normal matrices in...
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We propose a method of Lanczos type for solving a linear system with a normal matrix whose spectrum is contained in a second-degree curve. This is a broader class of matrices than that of the (l, m)-normal matrices introduced in a recent paper by Barth and Manteuffel. Our approach is similar to that of Huhtanen in the sense that both use the condensed form of normal matrices discovered by Elsner and Ikramov. However, there are a number of differences, among which are: (i) our method is modeled after the SYMMLQ algorithm of Paige and Saunders;(11) it uses only one matrix-vector product per step;(iii) we provide effective means for monitoring the size of the residual during the process. Numerical experiments are presented.
A mathematical program is proposed for the highly nonlinear problem involving frictional contact. A program-pattern using the fast multipole boundary element method (FM- BEM) is given for 3-D elastic contact with fric...
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A mathematical program is proposed for the highly nonlinear problem involving frictional contact. A program-pattern using the fast multipole boundary element method (FM- BEM) is given for 3-D elastic contact with friction to replace the Monte Carlo method. A new optimized generalized minimal residual (gmres) algorithm is presented. Numerical examples demonstrate the validity of the program-pattern optimization model for node-to-surface contact with friction. The gmres algorithm greatly improves the computational efciency.
In this paper, we state in a new form the algebraic problem arising from the one-field displacement finite element method (FEM). The displacement approach, in this discrete form, can be considered as the dual approach...
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In this paper, we state in a new form the algebraic problem arising from the one-field displacement finite element method (FEM). The displacement approach, in this discrete form, can be considered as the dual approach (force or equilibrium) with subsidiary constraints. This approach dissociates the nonlinear operator to the linear ones and their sizes are linear functions of integration rule which is of interest in the case of reduced integration. This new form of the problem leads to an inexpensive improvement of FEM computations, which acts at local, elementary and global levels. We demonstrate the numerical performances of this approach which is independent of the mesh structure. Using the gmres algorithm we build, for nonsymmetric problems, a new algorithm based upon the discretized field of strain. The new algorithms proposed are more closer to the mechanical problem than the classical ones because all fields appear during the resolution process. The sizes of the different operators arising in these new forms are linear functions of integration rule, which is of great interest in the case of reduced integration. (C) 2003 Elsevier B.V. All rights reserved.
A solver is developed for time-accurate computations of viscous flows based on the conception of Newton's method.A set of pseudo-time derivatives are added into governing equations and the discretized system is so...
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A solver is developed for time-accurate computations of viscous flows based on the conception of Newton's method.A set of pseudo-time derivatives are added into governing equations and the discretized system is solved using gmres *** to some special properties of gmres algorithm,the solution procedure for unsteady flows could be regarded as a kind of Newton *** physical-time derivatives of governing equations are discretized using two different approaches,i.e.,3-point Euler backward,and Crank-Nicolson formulas,both with 2nd-order accuracy in time but with different truncation *** turbulent eddy viscosity is calculated by using a version of Spalart-Allmaras one-equation model modified by authors for turbulent *** cases of unsteady viscous flow are investigated to validate and assess the solver,i.e.,low Reynolds number flow around a row of cylinders and transonic bi-circular-arc airfoil flow featuring the vortex shedding and shock buffeting problems,***,comparisons between the two schemes of timederivative discretizations are carefully *** is illustrated that the developed unsteady flow solver shows a considerable efficiency and the Crank-Nicolson scheme gives better results compared with Euler method.
The Robin iteration procedure is a technique for the FEM computation of electromagnetic scattering fields in unbounded domains. It is based on the iterative improvement of the known term of a non-homogeneous Robin con...
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The Robin iteration procedure is a technique for the FEM computation of electromagnetic scattering fields in unbounded domains. It is based on the iterative improvement of the known term of a non-homogeneous Robin condition on a fictitious boundary enclosing the scatterer. In this paper it is shown that the procedure is equivalent to the application of the Richardson method to a reduced system and that the use of gmres significantly reduces the computational effort.
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