The primary objective of this investigation is to determine experimentally the sources jet mixing noise. In present study, four different approaches are used. It reasonable assume that characteristics noise imprinted on their radiation fields. Under assumption, it becomes possible analyse far-field sound and then infer back sources. first approach make use spectral directional information measured by a single microphone in far field. A detailed analysis large collection data has been carried...

It is well known that when a high subsonic (Mach number > 0.7) Reynolds (Re 2 × 105) jet directed normal to wall intense discrete frequency sound waves called impingement tones are emitted. This phenomenon has been studied by of investigators in the past. generally accepted generated feedback loop. Despite this general agreement critical difference opinion as how achieved remains unresolved. Early (e.g. Wagner 1971; Neuwerth 1973, 1974) proposed loop closed acoustic disturbances which...

The main objective of this paper is to provide guidelines for designing and calibrating a high quality, static, jet-noise research facility making high-quality jet noise measurements. Particular emphasis placed on methodology determining if internal dominant in the spectrum. A section document devoted clarifying terminology associated with microphone frequency response corrections providing step-wise description other that must be applied measured raw spectra before data can considered...

The flow structure of a 50.8 mm (2 in) diameter jet operated at full expanded Mach number 1.37, with Reynolds numbers in the range 1.7 to 2.35 million, was examined for first 20 diameters. To facilitate study large scale structure, and determine any coherence, discrete tone acoustic excitation method used. Phase locked visualization as well laser velocimeter quantitative measurements were made. main conclusions derived from this are: (1) coherent like turbulence structures do exist...

Acoustic and flow visualization data from nozzles mounted on the same facility were acquired, a total of 10 different concepts jet noise suppression evaluated relative to one another also round nozzle. All had exit area. The suppressors included noncircular shapes; fitted with notches, tabs, ejectors; coaxial rectangular nozzles. Narrow-band acquired by microphone located in plane exit. In general, it is found that, for constant area, nozzle noisiest. Just about any modification this around...

*† ‡ § The primary object of this investigation is to determine experimentally the sources jet noise. In present study, four different approaches are used. It reasonable assume that characteristics noise imprinted on their radiation fields. Under assumption, it becomes possible analyze far field sound and then infer back sources. first approach make use spectral directional information measured by a single microphone in field. A detailed analysis large collection data has been carried out....

Recent progress in the field of active noise control is reviewed. The advent digital computer and subsequent speed capacity improvements have made more practical encouraged rapid advancement research. Several surveys research been done past, so emphasis placed on newest most innovative In particular, during decade eighties

It is well known that screech tones from supersonic jets are generated by a feedback loop. The loop consists of three main components. They the downstream propagating instability wave, shock cell structure in jet plume, and acoustic waves immediately outside jet. Evidence will be presented to show frequency largely controlled characteristics waves. driven wave Thus tone intensity its occurrence dictated wave. In this paper dependence spectrum on azimuthal mode number (axisymmetric or...

Detailed and well-controlled acoustic as well turbulence measurements are made of a tone-excited jet to obtain an understanding the mechanism broadband noise augmentation. Results presented for range excitation frequencies levels both with without flight simulation. large-scale instability waves within excited also described. Changes in radiated flow structure their interrelationship then discussed.