非均匀色散介质透射散射方法研究

发布时间：2018-04-24 04:16

本文选题：FDTD + 雷达散射截面积　；参考：《电子科技大学》2015年硕士论文

【摘要】：FDTD(Finite Difference Time Domain)方法是电磁计算领域的一种非常重要的方法,它基于蛙跳方法求解麦克斯韦方程组的微分项。作为一种时域方法,FDTD被广泛应用于研究非均匀色散媒质对电磁波的透射、散射作用。随着人们对电磁问题研究的不断深入,计算模型的空间尺寸不断增大,复杂程度不断升高。由于courant稳定性条件和数值色散的限制了时间步长和空间步长的选取,这些复杂电磁的计算时间和内存占用也随着网格数目而增加。进而,本文在非均匀色散媒质的计算中引入了非均匀网格技术以及并行计算技术来缩短计算时间、减少内存使用。本文首先阐述了FDTD领域的重要原理,对于信号源、吸收边界做了介绍。并通过金属、介质、金属-介质复合目标的散射验证了远场外推的准确性。针对非磁化等离子体、磁化等离子体,给出了PLRC方法的详细推导,并计算了分层、非均匀的非磁化等离子体、磁化等离子体的透射、散射问题。接着,针对非均匀网格方法,本文介绍了亚网格技术和缓变网格技术。将缓变网格技术引入到非均匀色散介质的计算当中,并给出了详细的推导。接着,通过求解双层、四层非均匀等离子体球的散射特性,验证了缓变网格方法的数值准确性。之后给出了缓变网格方法和均匀网格方法在计算时间、消耗内存上的对比,很好的体现出该方法的有效性。最后,本文介绍了并行技术中的MPI方法和Open MP方法。再简单对比两种方法后,详细的讨论了Open MP方法以及在非均匀色散介质介质上的应用。通过求解三层、五层非均匀等离子体立方体的散射特性,验证了Open MP技术使用到色散媒质计算中的可行性。之后,通过并行深度、并行结构、并行调度的三个方面分别计算,详细讨论了并行性能的改善。
[Abstract]:The FDTD(Finite Difference Time domain method is a very important method in the field of electromagnetic computation. It is based on the leapfrog method to solve the differential subdivision of Maxwell's equations. As a time-domain method, FDTD is widely used to study the transmission and scattering of electromagnetic waves in inhomogeneous dispersive media. With the further study of electromagnetic problems, the space size and complexity of the computational model are increasing. Because the courant stability condition and numerical dispersion limit the choice of time step and space step, the computational time and memory footprint of these complex electromagnetic systems increase with the number of meshes. Furthermore, the non-uniform grid technology and the parallel computing technique are introduced to reduce the computing time and memory usage in the computation of non-uniform dispersive media. In this paper, the important principle of FDTD is introduced, and the signal source and absorbing boundary are introduced. The accuracy of far field extrapolation is verified by the scattering of metal, medium and metal-medium composite targets. For the unmagnetized plasma and magnetized plasma, the PLRC method is derived in detail, and the transmission and scattering problems of the layered, inhomogeneous and magnetized plasma are calculated. Then, this paper introduces subgrid technology and slow grid technology for non-uniform grid method. The slow grid technique is introduced into the calculation of inhomogeneous dispersive media, and a detailed derivation is given. Then, the numerical accuracy of the slow-varying grid method is verified by solving the scattering characteristics of two-layer and four-layer inhomogeneous plasma spheres. After that, the comparison of slow grid method and uniform grid method in computing time and memory consumption is given, which shows the effectiveness of this method. Finally, this paper introduces the MPI method and Open MP method in parallel technology. After comparing the two methods, the Open MP method and its application in inhomogeneous dispersive media are discussed in detail. By solving the scattering characteristics of three-layer and five-layer inhomogeneous plasma cubes, the feasibility of using Open MP technique in dispersive medium calculation is verified. Then, the improvement of parallel performance is discussed in detail by computing three aspects of parallel depth, parallel structure and parallel scheduling.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN011

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