Computational Electromagnetics and Its Applications

Transcription

1 Computational Electromagnetics and Its Applications

2 ICASE/LaRC Interdisciplinary Series in Science and Engineering Managing Editor: MANUEL D. SALAS /CASE, NASA Langley Research Center, Hampton, Virginia, U.S.A. VolumeS

3 Computational Electromagnetics and Its Applications edited by Thomas G. Campbell NASA Langley Research Center, Hampton, Virginia, U.S.A. R. A. Nicolaides Carnegie Mellon University, Pittsburgh, Pennsylvania, U.S.A. and Manuel D. Salas Institute for Computer Applications in Science and Engineering (/CASE), NASA Langley Research Center, Hampton, Virginia, U.S.A. SPRINGER SCIENCE+BUSINESS MEDIA, B.V.

4 A C.I.P. Catalogue record for this book is available from the Library of Congress. ISBN ISBN (ebook) DOI / Cover Dlustration The cover illustration shows the electric surface currents on a 3. 7 wavelength sized commercial transport configuration at a single phase angle of the time harmonic solution. The surface current solution was computed at nose-on incidence with a horizontally polarized electric field (not shown). The various contours (typically shown in color) represent the magnitude of the electric currents on the body due to the electric field. Typically, the low currents are shown in the blue color range, high currents are shown by the red to white color range. This illustration was provided by Mr. Kam Hom of the NASA Langley Research Center; computed with MOM3D (NASA CR ), a patch method of moments, and displayed with EM-ANIMATE (NASA TM-4539), a surface current and electric field display and animation code. EM-ANIMATE can display and animate the time harmonic solution of both electric fields and surface currents in real time. Printed on acid-free paper All Rights Reserved 1997 Springer Science+Business Media Dordrecht Originally published by Kluwer Academic Publishers in 1997 Softcover reprint of the hardcover 1st edition 1997 No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system, without written permission from the copyright owner.

5 TABLE OF CONTENTS Preface... vii Keynote Presentation L. N. Medgyesi-Mitschang Overview of EM Research in the Electromagnetic Research Branch at the Langley Research Center F. B. Beck, C. R. Cockrell, C. J. Reddy, and M. D. Deshpande Antenna Optimization Using the Genetic Algorithm Zwi Altman and Raj Mittra Electromagnetic Analysis for Microwave Applications J. C. Rautio CEM for Radar Cross Section Application M. I. Sancer, G. Antilla, Y. C. Ma, and R. McClary Reduced-Order Electromagnetic Modeling for Design-Driven Simulations of Complex Integrated Electronic Systems A. C. Cangellaris and M. Celek The True Origin of Spurious Solutions and Their A voidance by the Least-Squares Finite Element Method Bo-nan Jiang A Note on the Use of Divergence Boundary Conditions in CEM U. Kangro and R. Nicolaides Characteristic-Based Methods in Computational Electromagnetics J. S. Shang v

6 vi Parallel Hierarchical Solvers and Preconditioners for Boundary Element Methods A. Grama, V. Kumar, and A. Sameh Finite-Difference Time-Domain (FDTD) Computational Electrodynamics Simulations of Microlaser Cavities in One and Two Spatial Dimensions S. C. Hagness, S. T. Ho, and A. Taftove Large Hybrid Finite Element Methods for Electromagnetics J. L. Volakis, J. Gong, and T. Ozdemir Panel Discussion Summary and Recommendations List of Attendees

7 PREFACE This volume contains the proceedings of the first ICASE/LaRC Workshop on Computational Electromagnetics and Its Applications conducted by the Institute for Computer Applications in Science and Engineering and NASA Langley Research Center. We had several goals in mind when we decided, jointly with the Electromagnetics Research Branch, to organize this workshop on Computational Electromagnetics ( CEM). Among our goals were a desire to obtain an overview of the current state of CEM, covering both algorithms and applications and their effect on NASA's activities in this area. In addition, we wanted to provide an attractive setting for computational scientists with expertise in other fields, especially computational fluid dynamics (CFD), to observe the algorithms and tools of CEM at work. Our expectation was that scientists from both fields would discover mutually beneficial interconnections and relationships. Another goal was to learn of progress in solution algorithms for electromagnetic optimization and design problems; such problems make extensive use of field solvers and computational efficiency is at a premium. To achieve these goals we assembled the renowned group of speakers from academia and industry whose talks are contained in this volume. The papers are printed in the same order in which the talks were presented at the meeting. The first paper is an overview of work currently being performed in the Electromagnetic Research Branch at the Langley Research Center. This paper is written by Beck, Cockrell, Reddy, and Deshpande. Following this is a paper by Altman and Mittra on the application of genetic algorithms to ultra broadband antenna optimization. These algorithms, while not necessarily inexpensive to use, are very robust, parallelizable and easy to implement. The next paper, by Rautio is on microwave applications. He gives a careful discussion of the sources and types of errors encountered in Method of Moment calculations for microwave circuits. This is followed by a paper by Sancer and co-workers on RCS computations. Their paper discusses the SWITCH code and its applications. This is a finite volume code using curvilinear hexahedral elements. The next paper by Cangellaris and Celik is concerned with reduced order modeling. This entails the use of a variety of different techniques for reducing the number vii

8 viii of degrees of freedom required to model complex systems. Typically, these techniques can be used to interpolate or extrapolate fields for additional parameter (e.g. frequency) ranges without engaging in new full field solutions. Jiang discusses the use of divergence boundary conditions. These provide a way to avoid the famous (or infamous) spurious mode problems encountered by simple minded finite element discretizations of Maxwell's equations. A postscript to this paper by Kangro and Nicolaides points out that there are situations where divergence boundary condition formulations are not equivalent to Maxwell's equations. The next paper, by Shang, is on the use of characteristic based solution algorithms. Of the algorithms used in CEM these are, perhaps, the ones closest to traditional CFD algorithms for hyperbolic equations. They work surprisingly well, given that they are inherently dissipative in contrast to the conservative Maxwell system. The paper by Grama, Kumar and Sameh discusses some.recent work on parallelizing multilevel vector-matrix multiply techniques and preconditioners. They show speedups of around four orders of magnitude for problems with hundreds of thousands of variables on a 256 processor Cray T3D. The well known finite difference time domain (FDTD) algorithm is represented in the paper of Hagness, Ho and Taflove. These authors apply the algorithm to computation of fields associated with nanoscale devices such as microlasers. The final paper by Volakis and co-authors provides a wide ranging guide to and valuable information about the application of finite elements to general electromagnetics computations. This paper intersects several of the earlier ones in that it covers reduced order techniques and parallel processing as well as far boundary conditions and other topics not covered in the earlier papers. The final article contains a transcript of a panel discussion which was held after the talks were completed. We have minimally edited this transcript to make it clearer. Finally, there is a list of registered participants at the end of the volume. We would like to thank the speakers for their contributions to a highly successful meeting and to the other participants for their lively participation in the meeting. The editors are also grateful to M. Yousuf Hussaini who was involved in the early planning of this workshop. As always, Emily Todd, the!case Conference Manager, performed her duties in a stellar manner. We would also like to thank Shannon Keeter of!case for organizing a disparate collection of papers into the uniform volume you are holding in your hands. In addition, we thank Deborah Ford of NASA Langley Research Center for transcribing the results of the panel session discussions and Brian Bailie of NASA Langley Research Center for graphics support. Tom Campbell Roy Nicolaides Manny Salas