Accession Number : AD0436676

Title :   THOUGHTS ON THE PROBLEM OF AERODYNAMIC NOISE SOURCES NEAR SOLID BOUNDARIES,

Corporate Author : ADVISORY GROUP FOR AERONAUTICAL RESEARCH AND DEVELOPMENT PARIS (FRANCE)

Personal Author(s) : Williams, J. E. Ffowcs

Report Date : APR 1963

Pagination or Media Count : 29

Abstract : The Report deals with a development of Curle's equations governing sound radiated by surface dipoles, which establishes, directly from those equations, the reflection phenomenon first noted by Powell. The development is for a particular situation, not easily treated by Powell's result, that of a turbulent boundary layer on a rigid flat plate radiating sound to a point so distant that the surface appears small. The development takes such a form that an estimate of the plate size, above which the dipole contribution vanishes and the plate assumes its role of an acoustic reflector, is made possible. The estimate, which is essentially an approximate one, suggests that surfaces have to be very large indeed before they become good reflectors. (Author)

Descriptors :   (*NOISE, AERODYNAMIC CHARACTERISTICS), REFLECTION, FLAT PLATE MODELS, ACOUSTIC PROPERTIES, TURBULENCE, TURBULENT BOUNDARY LAYER, SOUND TRANSMISSION, AIRCRAFT NOISE, PRESSURE.

Distribution Statement : APPROVED FOR PUBLIC RELEASE