Document Type
Thesis
Date of Award
5-31-1986
Degree Name
Master of Science in Electrical Engineering - (M.S.)
Department
Electrical Engineering
First Advisor
Edip Niver
Second Advisor
Gerald Martin Whitman
Third Advisor
Peter Engler
Abstract
Asymptotic ray theory (ART) is a widely used method dealing with problems of wave propagation in an inhomogeneous medium. The main deficiency of ART is in transition regions where rays near caustics, glancing and critical incidence fail to represent the actual wave field. Ray bundles in such transition regions have been successfully replaced with modal bundles and remainders El] in well defined profiles. However , in practical problems it is difficult to implement modal representations and almost impossible to express remainders. Recently emerging Gaussian beam method (GBM) has shown promising results in representing the total field produced by a source in terms of Gaussian beams [2].
A computer code SEIS.83 developed by Psencik and Cerveny to treat a horizontally and vertically varying inhomogeneous medium for point and line sources has been modified to accomodate Gaussian beams. The validity of the program has been tested on homogeneous and inhomogeneous profiles. Then, the developed Gaussian beam program is used to study the glancing ray transition region where CART) fails to represent a ray which is almost tangent to the bottom boundary, and a nearby bottom reflecting ray. This pair of transitional rays was replaced by bundles of gaussian beams.
Three major parameters that affected the ray and the beam equivalence are the beam width of an individual beam,the number of beams, and the width of the bundle. These parameters have been optimized to obtain accurate results to represent the transitional ray field. Reference solution for this problem is obtained from the numerical integration of the generalized rays. Results have also shown that replacement of glancing rays with Gaussian beams become more inaccurate as these rays start to experience many surface reflections.
Recommended Citation
Vogas, Michael Sotiriou, "Ray and beam representation of the glancing phenomena" (1986). Theses. 3393.
https://digitalcommons.njit.edu/theses/3393
