Experimental and Numerical Investigation of Electromagnetic Properties of Materials

Date

2019-05

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Abstract

  1. An efficient dielectric property measurement system is introduced in this paper. In the proposed measurement system, a parallel-disk sample holder with a new designed substrate is employed, which enables measuring the anisotropic input impedance of testing samples by rotating testing samples inside the holder. Moreover, a full-wave simulation method is utilized to numerically calculate anisotropic input impedances of samples under test using anisotropic permittivity and conductivity specified over a wide range. Anisotropic dielectric properties of a testing sample can then be estimated by comparing and correlating its experimental results and pre-computed simulation results. Additional look-up tables are numerically computed for different substrate materials. Based on the measured anisotropic input impedance and the known material property of the substrate, and then applying the fitting algorithm introduced in this paper, the dielectric properties of a certain material are computed from the corresponding look-up table. Uncertainty analysis for the measurement system is established to obtain rigorous results. Furthermore, a novel technique based on rotation matrices is performed to achieve fully anisotropic dielectric properties of the testing material.
  2. Accurate rock characterization is critical in using resistivity and dielectric methods for source rocks. However, conventional mixing theories cannot address scenarios where a high volume inclusion exists for rocks with anisotropic electrical parameters. In this paper, an electromagnetic numerical technique using the finite difference method was developed to investigate the electrical and anisotropic properties of source rocks based on 3D rock Micro-CT images. Numerical experiments were applied to study the effects of pyrites and fluids on the effective resistivity and electronic anisotropy in source rocks. It was found that less than 1% pyrite or brine significantly changed their electrical properties and enhanced their anisotropy.
  3. FDTD is a common approach to modeling 3D objects. The grid for a 3D object is complex in practical problems. It is a challenge to reduce computational time while maintaining a good accuracy. A preprocessing technique based on a numerical mixing law is introduced to improve the performance and efficiency of a 3D FDTD solver. The 3D FDTD solver used in this chapter is OpenEMS, which is a free and open source 3D FDTD solver written in C++.

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Keywords

Dielectric properties, Electromagnetics, Measurement system, Numerical investigation

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