DEVELOPMENT OF A MULTIGRID FDTD CODE FOR 3-DIMENSIONAL APPLICATIONS

Numerical modeling of realistic engineering problems using the finite- difference time-domain (FDTD) technique often requires more details th an possible when using a uniform-grid FDTD code, In this paper we desc ribe the development of a three-dimensional (3-D) multigrid FDTD code that focuses a large number of cells of small dimensions in the region of Interest. The detailed solution procedure is described and some te st geometries are solved using both a uniform-grid and the developed m ultigrid FDTD code to validate the results and check the accuracy of t he solution, Results from these comparisons as web as comparisons betw een the new FDTD code and another available multigrid code are present ed. In addition, results from the simulation of realistic microwave-si ntering experiments in large multimode microwave cavities are given to illustrate the application of the developed method in modeling electr ically large geometries, The obtained results show improved resolution In critical sites inside the 3-D multimode sintering cavity while kee ping the required computational resources manageable, It is shown that it is possible to simulate the sintering of ceramic samples of 0.318- cm wall thickness in a cylindrical multimode microwave cavity with a d iameter of 74 cm and a length of 112 cm using 2.23 x 10(6) total FDTD cells, For comparison, a total of 10(2) x 10(6) cells would have been required if a uniform-grid code with the same resolution had been used .