DIFFRACTION BY THE EDGE OF A 3-DIMENSIONAL OBJECT

The matched asymptotic expansions method is applied to investigate the problem of diffraction by the edge of a three-dimensional body at hig h frequencies. The present approach is an extension of a theory which was originally elaborated for plane screens [J. Acoust. Sec. Am. 97, 7 96-806 (1995)]. The theoretical analysis provides an asymptotic soluti on which is a refinement of physical optics: by the addition of two ed ge components as in the physical theory of diffraction. Explicit and s imple approximate solutions are derived to calculate the edge line int egrals leading to a practical integrative procedure that is well suite d to complex curved edges and that can overcome some disadvantages of ray theories. Last, the problem of diffraction by a finite cylinder is analyzed and a comparison with other asymptotic methods is shown. (C) 1996 Acoustical Society of America.