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High Order On-Surface Radiation Boundary Conditions in Electromagnetics

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2017, Doctor of Philosophy, University of Akron, Electrical Engineering.
This dissertation presents procedures for implementing high order boundary conditions in time and frequency domains for solving exterior problems governed by the Helmholtz equation and the wave equation exterior to a perfectly conducting scatterer. Solving problems governed by two and three-dimensional wave equations in exterior domains is a complex task. There are techniques to reduce the computational complexities; one technique is On-Surface Radiation Boundary Conditions (OSRBC). There has been a recent interest in revisiting this technique for two and three-dimensional problems [1]. In this research, we explore the implementation of a new high order OSRBC based on the high order local boundary conditions introduced in [2] for two and three dimensions to solve the wave equation in exterior domains. As will be seen later, the OSRBC implementations require normal derivatives of the scattered field on the surface of the scatterer. For the two-dimensional case, we develop a Fourier spectral method based on discrete Fourier transform to find the normal derivative of the electromagnetic field on the surface of the scatterer. The method involves transforming the high order time dependent local boundary conditions to frequency-domain and implementing it on the surface of the scatterer. The normal derivative of the scattered field is needed for applications such as the calculation of the radar cross-section and the surface current. We consider the two-dimensional problem for a perfectly conducting scatterer with arbitrary cross section. The numerical implementations and their performances for a wide range of frequencies are demonstrated and compared to the frequency-domain integral equation for the scattered field. The advantage of the new method is that the On- Surface Radiation Boundary Conditions (OSRBCs) is applicable to a wide range of frequencies. A series of numerical tests demonstrate the accuracy and efficiency of these conditions to a wide range of frequencies. Both the exact solutions, as well as the high order local boundary conditions solutions, are compared. For the two and three-dimensional time dependent wave equations cases, we simulate exact solutions in a large exterior domain because explicit solutions are not available. The implementation involves a new novel approach based on bilinear transformation, which simplified the implementation process and lead to higher accuracy compared to the different types of finite difference schemes used to approximate the first and second order partial derivative in the new high order OSRBC and the auxiliary functions that define the high order boundary conditions. A series of numerical tests demonstrate the accuracy and efficiency of the new high order OSRBC for two and three-dimensional problems. Both the long domain solutions, as well as the OSRBC solutions, are compared.
Subramaniya I. Hariharan (Advisor)
Arjuna Madanayake (Committee Member)
Nghi Tran (Committee Member)
Scott Sawyer (Committee Member)
J. Pat Wilber (Committee Member)
125 p.

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Citations

  • Al Weshah, Weshah, A. W. (2017). High Order On-Surface Radiation Boundary Conditions in Electromagnetics [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron150212307243821

    APA Style (7th edition)

  • Al Weshah, Weshah, Adel. High Order On-Surface Radiation Boundary Conditions in Electromagnetics. 2017. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron150212307243821.

    MLA Style (8th edition)

  • Al Weshah, Weshah, Adel. "High Order On-Surface Radiation Boundary Conditions in Electromagnetics." Doctoral dissertation, University of Akron, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron150212307243821

    Chicago Manual of Style (17th edition)