A finite difference thermal model of a cylindrical microwave heating applicator using locally conformal overlapping grids: part II--numerical results and experimental evaluation.

In this paper, we present numerical results obtained from a robust, locally conformal 3-D Orthogonal Grid Finite Difference (OGFD) thermal algorithm introduced in Part I of our current investigation [Al-Rizzo et al., 2006] integrated with an Orthogonal Grid Finite-Difference Time Domain (OGFDTD) scheme [Al-Rizzo et al., 2000], which accurately models the volumetric electromagnetic (EM) power deposition pattern.

A finite difference thermal model of a cylindrical microwave heating applicator using locally conformal overlapping grids: part I--theoretical formulation.

In this paper, we present a versatile mathematical formulation of a newly developed 3-D locally conformal Finite Difference (FD) thermal algorithm developed specificallyfor coupled electromagnetic (EM) and heat diffusion simulations utilizing Overlapping Grids (OGFD) in the Cartesian and cylindrical coordinate systems. The motivation for this research arises from an attempt to characterize the dominant thermal transport phenomena typically encountered during the process cycle of a high-power, microwave-assisted material processing system employing a geometrically composite cylindrical multimode heating furnace. The cylindrical FD scheme is only applied to the outer shell of the housing cavity whereas the Cartesian FD scheme is used to advance the temperature elsewhere including top and bottom walls, and most of the inner region of the cavity volume.

FDTD analysis of dielectric-loaded longitudinally slotted rectangular waveguides.

A versatile electromagnetic (EM) computational algorithm, based on the Finite-Difference Time-Domain (FDTD) technique, is developed to analyze longitudinally oriented, square-ended, single slot fixtures and slot-pair configurations cut in the broad wall of a WR-975 guide operating at a frequency of 915 MHz. The finite conductivity of the waveguide walls is accounted for by employing a time-domain Surface-Impedance Boundary Conditions (SIBC) formulation. The proposed FDTD algorithm has been validated against measurements performed on a probe-excited slot cut along the center line of the broad wall of a WR-284 guide and available experimental data for energy coupled from a longitudinal slot pair in the broad wall of a WR-340 guide.

Incorporation of the waveguide feed and cavity wall losses into a cartesian/cylindrical hybrid finite-difference time domain analysis of a geometrically-composite microwave applicator.

A Surface-Impedance Boundary Condition (SIBC) formulation is combined for the first time with a Cartesian/cylindrical hybrid Finite-Difference Time Domain (FD-TD) algorithm to investigate the effects on the electromagnetic characterization of a geometrically-composite microwave heating applicator introduced by the finite conductivity of the waveguide feed and cavity walls. The computational accuracy of the proposed scheme is validated in terms of the energy balance principle. Computer simulations revealed that the inclusion of wall losses has negligible effects on the interior field distribution and the reflection coefficient, S11.

Electromagnetic wave scattering by highly elongated and geometrically composite objects of large size parameters: the generalized multipole technique.

The potency and versatility of a numerical procedure based on the generalized multipole technique (GMT) are demonstrated in the context of full-vector electromagnetic interactions for general incidence on arbitrarily shaped, geometrically composite, highly elongated, axisymmetric perfectly conducting or dielectric objects of large size parameters and arbitrary constitutive parameters. Representative computations that verify the accuracy of the technique are given for a large category of problems that have not been considered previously by the use of the GMT, to our knowledge. These problems involve spheroids of axial ratios as high as 20 and with the largest dimension of the dielectric object along the symmetry axis equal to 75 wavelengths; sphere-cone-sphere geometries; peanut-shaped scatterers; and finite-length cylinders with hemispherical, spherical, and flat end caps.