SIMILARITY VARIABLES FOR SOUND RADIATION IN A UNIFORM FLOW

✍ Scribed by C.J. CHAPMAN

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 124 KB
• Volume: 233
• Category: Article
• ISSN: 0022-460X
• DOI: 10.1006/jsvi.1999.2800

✦ Synopsis

This paper derives a parametric family of similarity variables for describing sound radiation in a uniform #ow. The variables, based on a Lorentz-type transformation between the wave equation and the convected wave equation, contain Doppler factors and generalize the Prandtl}Glauert variables used in aerodynamics. The parameter specifying the family may be chosen to match the frequency dependence of the sound on the Mach number of the #ow in problem being solved. The variables are used to derive a &&fundamental rule'' for obtaining a solution of the convected wave equation from a solution of the unconvected wave equation; the rule does not correspond to a Galilean transformation. The method of the paper is applied to several examples from aeroacoustics, including a thickness-noise acoustic source modelled by the Ffowcs Williams}Hawkings equation; a point-force acoustic source; a spatially extended time-harmonic source; a duct mode; and the sound radiated during blade}vortex interaction.