Reza Attarnejad

Bio: Reza Attarnejad is an academic researcher from University of Tehran. The author has contributed to research in topics: Finite element method & Beam (structure). The author has an hindex of 17, co-authored 67 publications receiving 1040 citations. Previous affiliations of Reza Attarnejad include University College of Engineering & University of Kashan.

Numerical simulation of acoustic cavitation in the reservoir and effects on dynamic response of concrete dams

Abstract: This paper describes a numerical model and its finite element implementation that used to compute the cavitation effects on seismic behavior of concrete dam and reservoir systems. The system is composed of two sub-systems, namely, the reservoir and the dam. The water is considered as bilinear compressible and inviscid and the equation of motion of fluid domain is expressed in terms of the pressure variable alone. A bilinear state equation is used to model the pressure–density relationship of a cavitated fluid. A standard displacement finite element formulation is used for the structure. The Structural damping of the dam material and the radiation damping of the water and damping from foundation soil and banks have been incorporated in the analysis. The solution of the coupled system is accomplished by solving the two sub-systems separately with the interaction effects at the damreservoir interface enforced by a developed iterative scheme. The developed method is validated by testing it against problem for which, there is existing solution and the effects of cavitation on dynamic response of Konya gravity dam and Morrow Point arch dam subjected to the first 6 s of the May 1940 El-Centro, California earthquake, is considered. Obtained results show that impact forces caused by cavitation have a small effect on the dynamic response of dam-reservoir system.

Numerical Uncoupling of Domains in Dam-Reservoir Problem

Abstract: Flexibility of dam structure affects the hydrodynamic pressure acting on the dam. Several approaches have been proposed to consider this effect. Most of these approaches are involved with an iterative scheme. Of course solving the total numerical model including the dam and the reservoir is the most accurate method, but it has certain deficiencies. Using the frontal solution method of total model, dam structure, and fluid domain and keeping the interface degrees of freedom in the front is proposed in the current study. Having the solution of the interface degrees of freedom, the structure and fluid may be analyzed separately. The main advantage of the method lies in the fact that the accuracy of the results is the same as analysis of the total model, no iteration is necessary, combination of Lagrangian and Eulerian formulations for solid and fluid may be used, and the unknown variables are of the same order. Performing the analysis in time domain extends the method to nonlinear analysis if required.

A novel approach to solve linear systems arising from BEM using fast wavelet transforms

Abstract: This paper uses Daubechies orthogonal wavelets to change dense and fully populated matrices of boundary element method (BEM) systems into sparse and semi-banded matrices. Then a novel algorithm based on hierarchical nature of multiresolution analysis is introduced to solving resultant sparse linear systems. This algorithm decomposes NS-form of transformed parent matrix into descendant systems with reduced sizes and solves them iteratively using GMRES algorithm. Both parts, changing dense matrices to sparse systems and the novel solver, can be added as a black box to the existing BEM codes. Transforming matrices into wavelet space needs less time than saved by solving sparse large systems. Numerical results with a precise study on sensitivity of solution for physical variables to the thresholding parameter, and savings in computer time and memory are presented. Also, the suitable value for thresholding parameter is recommended for elasticity problems. The results indicate that the proposed method is efficient for large problems. Copyright © 2009 John Wiley & Sons, Ltd.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Introduction to the Finite Element Method

Abstract: This chapter introduces the finite element method (FEM) as a tool for solution of classical electromagnetic problems. Although we discuss the main points in the application of the finite element method to electromagnetic design, including formulation and implementation, those who seek deeper understanding of the finite element method should consult some of the works listed in the bibliography section.

Seismic Design Of Reinforced Concrete And Masonry Buildings

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