SOUND RADIATED FROM A CYLINDRICAL DUCT WITH KELLER'S GEOMETRICAL THEORY

✍ Scribed by S.T. HOCTER

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 252 KB
• Volume: 231
• Category: Article
• ISSN: 0022-460X
• DOI: 10.1006/jsvi.1999.2739

✦ Synopsis

An exact solution to the problem of radiation from a cylindrical duct has been available using the Wiener}Hopf technique for many years, and a number of approximate methods can also be considered. When parameter spaces involving high frequency are required, it is possible to use ray-theory-based techniques to solve the problem. Keller proposed such a method, introducing a geometrical theory of di!raction (GTD) which extended the concept of geometrical optics to account for di!racted rays. When a ray propagates inside the duct, it will re#ect o! the duct rim creating a Keller cone of singly di!racted rays, allowing formulae to be obtained for the singly di!racted "eld using Keller's GTD. Expressions for the singly di!racted "eld are presented, and then compared with the exact solution for a range of parameters. The choice of parameters is governed by a set of mode angles which are used in describing geometrically how a ray propagates through the duct and out into free space.