Yazar "Coskun, Safa Bozkurt" seçeneğine göre listele

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    An exact truncation boundary condition for incompressible fluid domains in dam-reservoir interaction analysis
    (ELSEVIER SCI LTD, 2007) Coskun, Safa Bozkurt
    In this paper, an exact truncation boundary condition is derived and implemented in a finite element code for the analysis of dam-reservoir interaction for incompressible, inviscid and unbounded fluid domains. The reservoir domain is divided into two regions in the derivation of the truncation boundary condition. These are the near field having a complex geometry and the far field with a uniform cross-section. The proposed boundary condition is obtained using the analytical solution for the far field and used as a truncation boundary condition at the truncation surface for the near field including the dam-reservoir system. This method has the advantage of geometrical flexibility in the near field and of being a semi-analytical approach giving close results to the exact solutions for the cases analyzed. In addition, accurate results are also obtained when the reservoir domain is truncated very close to the dam-reservoir interface. (c) 2006 Elsevier Ltd. All rights reserved.
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    Analysis of convective straight and radial fins with temperature-dependent thermal conductivity using variational iteration method with comparison with respect to finite element analysis
    (HINDAWI LTD, 2007) Coskun, Safa Bozkurt; Atay, Mehmet Tarik
    In order to enhance heat transfer between primary surface and the environment, radiating extended surfaces are commonly utilized. Especially in the case of large temperature differences, variable thermal conductivity has a strong effect on performance of such a surface. In this paper, variational iteration method is used to analyze convective straight and radial fins with temperature-dependent thermal conductivity. In order to show the efficiency of variational iteration method (VIM), the results obtained from VIM analysis are compared with previously obtained results using Adomian decomposition method (ADM) and the results from finite element analysis. VIM produces analytical expressions for the solution of nonlinear differential equations. However, these expressions obtained from VIM must be tested with respect to the results obtained from a reliable numerical method or analytical solution. This work assures that VIM is a promising method for the analysis of convective straight and radial fin problems. Copyright (C) 2007.
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    Comparative Analysis of Power-Law Fin-Type Problems Using Variational Iteration Method and Finite Element Method
    (HINDAWI PUBLISHING CORPORATION, 2008) Atay, Mehmet Tarik; Coskun, Safa Bozkurt
    Variational iteration method is applied to examine the temperature distribution within a single fin with a one-dimensional steady-state nonlinear heat conduction equation. Variation of temperature due to different levels of nonlinearities is analyzed. The results obtained by means of variational iteration method are compared with the results obtained from finite element method. A fourth iteration variational iteration solution is used in all cases considered. An error analysis is also conducted to evaluate the performance of proposed solution technique. The results have shown that variational iteration method is a powerful solution technique in the analysis of power-law fin-type problems. Copyright (C) 2008 M. T. Atay and S. B. Coskun.
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    Determination of Buckling Loads and Mode Shapes of a Heavy Vertical Column under its Own Weight Using the Variational Iteration Method
    (WALTER DE GRUYTER GMBH, 2010) Okay, Fuad; Atay, Mehmet Tarik; Coskun, Safa Bozkurt
    This paper applies the variational iteration method for finding buckling loads and mode shapes of a heavy column. The study shows efficiency of the method and accuracy of the obtained analytic approximate solution.
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    Determination of critical buckling load for elastic columns of constant and variable cross-sections using variational iteration method
    (PERGAMON-ELSEVIER SCIENCE LTD, 2009) Coskun, Safa Bozkurt; Atay, Mehmet Tarik
    In this paper, variational iteration method (VIM) is applied to the problem of determination of critical buckling loads for Euler columns with constant and variable cross-sections. VIM is a powerful method for the solution of nonlinear ordinary and partial differential equations and integral equations. Hence it is a suitable approach for the analysis of engineering problems where an exact solution is difficult to obtain. This study presents the application of VIM to various buckling cases and results are produced for columns with different support conditions and with different variation of cross-sections. The results obtained are accurate which show that variational iteration method is a very efficient technique in the analysis of elastic stability problems. (C) 2009 Elsevier Ltd. All rights reserved.
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    Determination of Critical Buckling Loads for Euler Columns of Variable Flexural Stiffness with a Continuous Elastic Restraint Using Homotopy Perturbation Method
    (WALTER DE GRUYTER GMBH, 2009) Coskun, Safa Bozkurt
    In this paper, stability analysis of continuously restrained Euler columns of variable flexural stiffness is conducted by using homotopy perturbation method (HPM). The restraint considered in this study is an elastic foundation model in engineering practice and it is of great interest to foundation engineers. Critical buckling loads are investigated considering different end conditions. Obtaining analytical solutions for these types of problems was very difficult, now the condition is changed. The study proves that HPM is a very efficient and promising approach to the elastic stability analysis of specified problems.
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    Effects of nonlinearity on the variational iteration solutions of nonlinear two-point boundary value problems with comparison with respect to finite element analysis
    (HINDAWI LTD, 2008) Atay, Mehmet Tarik; Coskun, Safa Bozkurt
    Solution of a nonlinear two-point boundary value problem is studied using variational iteration method (VIM) considering its convergence behavior due to the changing nonlinearity effects in the equation. To achieve this, steady Burger equation is first solved by using finite element method (FEM) with a very fine mesh for the comparison of results obtained from VIM. Effect of the nonlinear term in the equation that is multiplied by a constant is taken into account for five different cases by changing the corresponding constant. Results have shown that VIM is a flexible, easy to apply, and promising method for the analysis of nonlinear two-point boundary value problems with the fact that the larger the effect of the nonlinear term of the equation, the slower the convergence rate when compared to FEM solutions. Copyright (C) 2008 M. T. Atay and S. B. Coskun.
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    Elastic stability of Euler columns with a continuous elastic restraint using variational iteration method
    (PERGAMON-ELSEVIER SCIENCE LTD, 2009) Atay, Mehmet Tarik; Coskun, Safa Bozkurt
    In this paper, analysis of elastic stability for continuously restrained Euler columns is conducted by means of variational iteration method (VIM). A uniform homogeneous column is assumed to be restrained along its length. The restraint considered in this study is an elastic foundation model in engineering practice and it is of great interest to foundation engineers. Hence, the variation of the critical buckling loads with the stiffness of elastic restraint is investigated using VIM for the restrained columns with different end conditions. Obtaining analytical solutions for these types of problems is not a simple procedure since the equations of stability criteria are highly nonlinear. This study presents the application of VIM for obtaining exact solutions for continuously restrained Euler columns. The study proves that VIM is a very efficient and promising approach in the elastic stability analysis of specified problems. (C) 2009 Elsevier Ltd. All rights reserved.
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    Fin efficiency analysis of convective straight fins with temperature dependent thermal conductivity using variational iteration method
    (PERGAMON-ELSEVIER SCIENCE LTD, 2008) Coskun, Safa Bozkurt; Atay, Mehmet Tarik
    For enhancing heat transfer between primary surface and the environment, utilization of radiating extended surfaces are common. Especially for large temperature differences; variable thermal conductivity has a strong effect on performance of such a surface. In this paper, variational iteration method is used to analyze the efficiency of convective straight fins with temperature dependent thermal conductivity. VIM produces analytical expressions for the solution of nonlinear differential equations. In order to show the effectiveness of Variational iteration method (VIM). the results obtained from VIM analysis is compared with available solutions obtained using Adomian decomposition method (ADM) and the results from finite element analysis. This work assures that VIM is it promising method for the efficiency analysis of convective straight fin problems. (C) 2008 Elsevier Ltd. All results reserved
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    Homotopy perturbation method for free vibration analysis of beams on elastic foundation
    (IOP PUBLISHING LTD, 2010) Ozturk, Baki; Coskun, Safa Bozkurt; Koc, Mehmet Zahid; Atay, Mehmet Tarik; Khalili, N; Valliappan, S; Li, Q; Russell, A
    In this study, the homotopy perturbation method (HPM) is applied for free vibration analysis of beam on elastic foundation. This numerical method is applied on a previously available case study. Analytical solutions and frequency factors are evaluated for different ratios of axial load N acting on the beam to Euler buckling load, N-r. The application of HPM for the particular problem in this study gives results which are in excellent agreement with both analytical solutions and the variational iteration method (VIM) solutions for the case considered in this study and the differential transform method (DTM) results available in the literature.
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    Numerical and Soft Computing Methods for Characteristic Value Problems of ODE and ODEs Systems
    (HINDAWI PUBLISHING CORPORATION, 2013) Atay, Mehmet Tarik; Simonetti, Biagio; Coskun, Safa Bozkurt; Venkatesan, D.; Basaran, Murat Alper; Squillante, Massimo
    [Abstract Not Available]
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    The Homotopy Perturbation Method for free vibration analysis of beam on elastic foundation
    (TECHNO-PRESS, 2011) Ozturk, Baki; Coskun, Safa Bozkurt
    In this study, the homotopy perturbation method (HPM) is applied to free vibration analysis of beam on elastic foundation. This numerical method is applied on three different axially loaded cases, namely: 1) one end fixed, the other end simply supported; 2) both ends fixed and 3) both ends simply supported cases. Analytical solutions and frequency factors are evaluated for different ratios of axial load N acting on the beam to Euler buckling load, N(r). The application of HPM for the particular problem in this study gives results which are in excellent agreement with both analytical solutions and the variational iteration method (VIM) solutions for all the cases considered in this study and the differential transform method (DTM) results available in the literature for the fixed-pinned case.