Sound generation by heated subsonic jets

✍ Scribed by F. Obermeier

• Publisher: Elsevier Science
• Year: 1975
• Tongue: English
• Weight: 594 KB
• Volume: 41
• Category: Article
• ISSN: 0022-460X
• DOI: 10.1016/s0022-460x(75)80109-x

✦ Synopsis

The noise generation by the turbulent mixing of a heated, subsonic jet and its cold surroundings is discussed, with the help of the method of matched asymptotic expansions, separately for an inner region where hydrodynamical characteristics dominate and for an outer region where sound fields prevail. The actual calculations then can be confined to the inner region since the first approximation of the outer solution depends only on the multipole-character of the inner solution. For a first inner approximation compress-. ibility effects are negligible, and the flow field can be described by the incompressible approximation of the flow equations.

With account taken of matching conditions, a Uo%power law can be realized if monopole sources with a strength ~U~ exist. Such monopole-like sources are possible only if there is a mass flow between the heated and the cold gas flow due to the diffusion caused by temperature gradients. This effect can be included by abandoning the usually applied assumption dS/dt = 0 (S being the entropy).

A qualitative assessment of the order of magnitude of these effects is given.