By A.S. Ginevsky, Y.V. Vlasov, R.K. Karavosov
Results of experimental examine on aerodynamic and acoustic keep watch over of subsonic turbulent jets by means of acoustic excitation are offered. It used to be proven that those keep an eye on equipment, originated by means of authors, not just can accentuate blending (by acoustic irradiation at low frequency), but additionally significantly ease it (at high-frequency irradiation). This study monograph offers the up-to-date result of the authors supplemented by means of different investigations carried out in united states, Germany and nice Britain. The equipment for the numerical simulation of subsonic turbulent jets below acoustic excitation are defined intimately, and examples are reviewed of useful functions, together with aid of turbojet engine noise and acoustic keep an eye on of self-sustained oscillations in wind tunnels.
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Additional resources for Acoustic Control of Turbulent Jets
IA. 05 o 2 4 6 8 10 12 14 x/d o 1 Q 2 c 4 v 3 o 2 4 6 8 10 12 14 x/d Fig. 24. The mixing intensification in a circular jet with square generators of longitudinal vortices (the square side is a = d /16); 1) without generators, 2) 8 generators, 3) 4 generators, 4) 2 generators. c. The jet issue from a circular nozzle with generators of longitudinal vortices. 3]. Fig. 24 presents the change in the average velocity and longitudinal velocity pulsations along the jet axis. The corresponding curves for a circular nozzle without voftex generators are shown for comparison purposes.
0 0 0 0 decreases with decreasing rp and the contribution of low-frequency components correspondenty increases. In addition, the maximum becomes more and more distinct in the noise spectra for such a change of the noise spectral composition. The most perceptible change of the noise spectra is observed for small values of the angle rp = 30°- 45°. The pressure pulsations do not coincide in phase with the velocity pulsations near the border of the turbulent jet mixing area. e. the distance between the sound source and receiver should be large relative to the source sizes and the sound wavelength, are not fulfilled.
Consider the simplest schemes of single-frequency acoustical excitation of jets. The jet longitudinal (downstream and upstream), transverse and radial irradiation (Fig. 1) are recognized. For a jet under longitudinal and radial excitation by sound waves, axisymmetric periodic al vortex rings are generated at the nozzle edge and carried away downstream. 42]. They are more intensive at the emitter side and less intensive at the opposite side. This A. S. , Acoustic Control of Turbulent Jets © Springer-Verlag Berlin Heidelberg 2004 34 CHAPTER 2.