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TDFEM Based on New Difference Schemes and Its Shielding Effectiveness Analysis of Enclosures

Author: ZhaoZuo
Tutor: HeXiaoXiang
School: Nanjing University of Aeronautics and Astronautics
Course: Electromagnetic Field and Microwave Technology
Keywords: TDFEM temporal discretization new difference schemes UWB electromagnetic pulse aperture coupling SE
CLC: TN011
Type: Master's thesis
Year: 2012
Downloads: 39
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Abstract


In order to ensure the computational accuracy and also to improve computational efficiency, toreduce memory consumption, the analysis procedure in the three-dimensional time-domain finiteelement method (TDFEM) is optimized in this study. TSFD technique is employed to divide thecomputational domain and then the of equivalent functional is derived; the first-order Mur absorbingboundary conditions is used to truncate the computational domain; it is modeled and meshed by theMSC.Patran software; the edge based tangential vector basis functions are utilized to simulate theelectric field; the volume excitation method is employed to introduce incident wave in the total fielddomain; sparse matrix storage technique is adopted due to the characteristics of TDFEM coefficientmatrix. Moreover, from our numerical experiments result, the time discretization scheme in TDFEMnot only affects the time step size choice, but also affects the time cost and computational accuracy.In this study, the different temporal discretization schemes in TDFEM are investigated. Thestability analysis for central difference, backward difference, forward difference and Newmarkmethods in TDFEM are carried out. Some temporal discretization optimization options are obtainedvia comparisons of computation efficiency, computation accuracy and memory cost in differentdifference methods with various time step sizes. Numerical results show that the Newmark method isa better choice which can reach higher accuracy with bigger time step size. And the Newmark methodcan choose2to4times bigger time step size than center difference method in the stable time step sizeregion and has the highest accuracy.On this basis, linear acceleration method and Houbolt method of computational structuraldynamics are applied to TDFEM as new difference schemes, to further improve the time temporaldiscretization options. The results show that linear acceleration method allows the maximum time stepto be3～(1/3)times bigger t than center difference method in the stable time step size region. When thetime step restriction is not significant, linear acceleration method can achieve higher accuracy.Although Houbolt metod is a little bit worse than the Newmark method in terms of accuracy, it is stillan alternative method as an unconditionally stable scheme. Furthermore, the numerical resultsdemonstrate that both the linear acceleration method and the Houblot method have a optimal time stepsize range which are2to3times of the critical time step size and the maximum central differencetime step size, respectively.Finally, shielding effectiveness of metallic enclosures with apertures excited by electromagnetic pulse is analyzed with TDFEM. The incident UWB electromagnetic pulse plane-wave within thetotal-region is achieved by interpolation from an auxiliary1-D FDTD grids, and linear accelerationmethod as well as Newmark method is applied to discretize time. As a result, the electromagneticresponse and the spectrum characteristic can be obtained. With different way of incidentelectromagnetic pulse and different configurations of apertures, coupling effect of enclosures excitedby electromagnetic pulse is investigated, and impact factors of shielding effectiveness is furtherdiscussed through frequency spectral analysis. In addition, the aperture filled with dielectric materialis also studied for shielding effectiveness. The simulation results will benefit the practical shieldingdesign for electronic equipment and electromagnetic protection in electromagnetic pulse environment.

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