Accession Number : ADA326366

Title :   Fluctuating Dilatation Rate as an Acoustic Source.

Descriptive Note : Contractor rept.,

Corporate Author : INSTITUTE FOR COMPUTER APPLICATIONS IN SCIENCE AND ENGINEERING HAMPTON VA

Personal Author(s) : Ristorcelli, J. R.

PDF Url : ADA326366

Report Date : 1997

Pagination or Media Count : 11

Abstract : Ribner's (1962) dilatational acoustic theory is revisited. A rigorous connection between the fluctuating dilatation rate and the acoustic source field is established; this vindicates Ribner's heuristic contention while indicating additional acoustic source terms in his dilatational acoustic theory. It is also shown that Ribner's acoustic source term is quadrupole. Interesting consequences of the dilatational point of view are indicated. It is found that in the region of vortical fluid motion the dilatation scales as the square of the turbulent Mach number, and has little to do with the acoustic field; its time rate of change, however, is a portion of the sound generation mechanism. Away from the vortical region the fluid dilatation is an acoustic variable and scales. The mathematical link established is useful to interpreting direct numerical simulation of aeroacoustical flows in which the dilatation is computed.

Descriptors :   *NUMERICAL ANALYSIS, *ACOUSTICS, *FLUID MECHANICS, COMPUTERIZED SIMULATION, TURBULENCE, QUADRUPOLE MOMENT, VORTICES, HEURISTIC METHODS, MACH NUMBER, ACOUSTIC FIELDS, SOUND GENERATORS.

Subject Categories : Numerical Mathematics
      Acoustics
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE