Jet Noise

On the Scaling Laws and Similarity Spectra for Jet Noise in Subsonic and Supersonic Flow

“…Accordingly they proposed the existence of two universal (but empirical) similarity spectrum functions F and G , such that the overall jet noise spectrum is expressed as (19) where F(f /fL) is a spectrum for the large-scale turbulence/instability waves (characteristic of It is interesting to note that the Ribner spectrum matches well with the large-scale turbulence noise spectrum due to Tam for frequencies below the peak frequency, whereas it compares better with Tam's fine-scale turbulence noise spectrum beyond the peak frequency except at very large frequencies. The intersection of Tam's large scale and small scale spectra at high frequencies points to a difficulty from the point of view of sound generation.…”

Mean and fluctuating velocity contours and acoustic characteristics of subsonic and supersonic jets

“…Lighthill 5 derived an equation for the overall sound power for subsonic jets by using available experimental data and dimen sional analysis as…”

“…17 -19. 5 Lighthill 4 showed that a fluctuating flow of gas in a turbu lent jet generates in the surrounding atmospnere the same fluctuations of density as would be produced in a classical stationary acoustic medium by a system of external applied stresses. And the radiated sound is due to the turnulent flow which does not react significantly upon it for subsonic flow velocities.…”

Subsonic and Supersonic Jets and Supersonic Suppressor Characteristics

“…19b. Downstream of the supersonic region in the fully developed subsonic turbulent flow the acoustic radiation per unit length of the jet decreased as x~6, which was postulated by Lighthill 17 for a subsonic jet. where m = PJ UjA is the mass flow of the jet.…”