Download Acoustic Control of Turbulent Jets by A.S. Ginevsky, Y.V. Vlasov, R.K. Karavosov PDF

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 through acoustic excitation are offered. It used to be tested that those keep an eye on tools, originated via authors, not just can accentuate blending (by acoustic irradiation at low frequency), but additionally particularly ease it (at high-frequency irradiation). This examine monograph provides the up-to-date result of the authors supplemented through different investigations carried out in united states, Germany and nice Britain. The tools for the numerical simulation of subsonic turbulent jets less than acoustic excitation are defined intimately, and examples are reviewed of functional purposes, together with aid of turbojet engine noise and acoustic regulate of self-sustained oscillations in wind tunnels.

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33. Petersen RA (1979) Influence of wave dispersion on vortex pairing in a jet. 34. Rabinovich MI, Sushchik MM (1983) Coherent structures in turbulent flows (in Russian). In: Nonlinear waves. 35. Roshko A (1976) Structure of turbulent shear flows: A new look. 36. Sorkin LI (ed) (1968) Ca1culations and measurements of characteristics of noise generated in the far noise field by jet airplanes (in Russian). 37. Sreenivasan KR (1984) The azimuthal correlations of velocity and temperature fluctuations in an axisymmetric jet.

The acoustical field was generated by a dynamic loudspeaker mounted on the face wall of the receiver (Fig. 16). 10 5 • The successive nozzle lengthening changed naturally the flow mode in the initial boundary layer from laminar to turbulent without use of turbulators. The slight drawback of this method of the boundary layer turbulization is the sensible change in the relative thickness of the initial boundary layer, 8 0 / ro ' where ro = d / 2. The sound pressure level at the nozzle oudet section was L = 120 - 125 dB.

46 CHAPTER 2. 1 ,----------------------------------, • 1 .. L-_ _ _ _----' 1 2 4 6 8 x/d Fig. 14. Change of u / u_ a10ng the jet axis for Uo = 10 mls, St s =9 1) L = 105 dB, 2) L = 135 dB. 02 St e Fig. 15. 5%,2) u;/u o =2%,3) u;/u o =3 %,4) u;/u o =4 %. 3. Effect of the Flow Regime in the Boundary Layer at the Nozzle Edge In the first experiments for acoustical excitation of turbulent jets the flow mode in the initial boundary layer at the nozzle outlet section was not controlled. However, it emerged that the mixing intensification and attenuation effects in a jet under acoustical irradiation depend appreciably on the flow mode in the boundary layer near the nozzle outlet.

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