Archives of Acoustics, 1, 3, pp. 181-200, 1976

Flow patterns and noise of a choked gas jet expanding into a duct

Krystyna J. Witczak
Warsaw Technical University
Poland

Axi-symmetric, choked air outflow into a duct with an abrupt enlargement of its cross-section was investigated in order to establish the relations between the flow pattern and the aerodynamic noise generated. Four main kinds of flow structure, possessing different acoustic properties, were found in the cases studied of the outflow from convergent circular and annular nozzles. These patterns correspond to the occurrence of: cellular structure, self-excited oscillations, single shock wave (noise minimum) and supersonic flow. An acoustic feedback type source of sound can appear under certain circumstances in the cellular structure. The self-excited shock wave and pressure oscillations produce noise characterized by discrete frequencies in the sound pressure level spectrum. The reasons for the minimum noise generation, which takes place before the reattachment of the supersonic stream boundary to the duct wall, are explained. Prevention of strong oscillations by the insertion of spoilers at the nozzle lip reduces the noise significantly over a wide range of supply pressures, however it increases the noise minimum due to turbulence intensity growth. Recommendations for nozzle and duct geometry for noise reduction are given.
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Copyright © Polish Academy of Sciences & Institute of Fundamental Technological Research (IPPT PAN).

References

M.J. LIGHTHILL, Sound generated aerodynamically, The Bakerian Lecture 1961 Proceedings of the Royal Society of London, Series A, 267, 147-182 (1962).

H.S. RIBNER, The generation of sound by turbulent jets, Academic Press, Advances in Applied Mechanics, 8, 103-182 (1964).

M.J. LIGHTHILL, Jet noise, AIAA Journal, 1, 7, 1507-1517 (1963).

M.J. FISHER, P.A. LUSH, M. HARPER BOURNE, Jet noise, Journal of Sound and Vibration, 28, 3, 563-585 (1973).

V.M. MAMIN, A.V. RIMSKI-KORSAKOV, Supersonic air jet as the source of sound [in Russian], Physics of aerodynamic noise, Publ. SCIENCE, Moscow 1967, p. 77-82.

J.E. FrowCS WILLIAMS, Jet noise at very low and very high speed, Aerodynamic noise, Proceedings of AFOSR-UTIAS Symposium, Toronto 1968, p. 131-146.

J.B. LARGE, J.F. WILBY, E. GRANDE, A.0. ANDERSSON, The development of engineering practices in jet, compressor, and boundary layer noise, Aerodynamic noise, Proceedings of AFOSR-UTIAS Symposium, Toronto 1968, p. 43-67.

K.A. BISHOP, J.E. FFOWCS WILLIAMS, W. SMITH, On the noise sources of the unsuppressed high-speed jet, Journal of Fluid Mechanics, 50, 1, 21-31 (1971).

V.M. MAMIN, A.V. RIMSKI-KORSAKOV, Some properties of discrete sound emission by supersonic air jet, [in Russian], Proceedings of 7th All-Union Acoustic Conference of Physical and Technical Acoustics, 1971, p. 233-236.

A. POWELL, Nature of the feedback mechanism in some fluid flows producing sound, 4th International Congress on Acoustics, Copenhagen 1962, paper 0-22.

A. POWELL, On the noise emanating from a two-dimensional jet above the critical pressure, The Aeronautical Quarterly, 4, 103-122 (1953).

A. POWELL, On the mechanisms of choked jet noise, Proceedings of the Physical Society, Section B, 66, part 12, 408 B, 1039-1056 (1953).

M.G. DAVIES, D.E. OLDFIELD, Tones from a choked axisymmetric jet, Acustica, 12, 4, 257-277 (1962).

R. WESTLEY, J.H. WOOLLEY, An investigation of the near noise fields of a choked axi-symmetric air jet, Aerodynamic noise, Proceedings of AFOSR-UTIAS Symposium, Toronto 1968, p. 147-167.

G. NEUWERTH, Acoustic feedback of a subsonic and supersonic free jet which impinges on an obstacle, 5th DGLR-Meeting, Berlin 1972.

D. MIDDLETON, E.J. RICHARDS, Discrete frequency noise from ejector nozzles, 4th International Congress on Acoustics, Copenhagen 1962, paper L 21.

D. MIDDLETON, Theoretical and experimental investigations into the acoustic output from ejector flows, Journal of Sound and Vibration, 11, 4, 447-473 (1970).

J.S. ANDERSON, T.J. WILLIAMS, Base pressure and noise produced by the abrupt expansion of air in a cylindrical duct, Journal of Mechanical Engineering Science, 10, 3, 262-268 (1968).

J.S. ANDERSON, The noise from abruptly expanded jets, EUROMECH 34, Colloquium on Control and Feedback Mechanisms in Flow Noise, Göttingen 1972.

E. KOPPE, E.A. MÜLLER, Modellversuche zur Klärung von Geräusch- und Vibra- tionsfragen an Reduzierventilen, Mitteilungen der Vereinigung der Grosskesselbesitzer, 41, 65-83 (1956).

A. NAKANO, Characteristics of noise emitted by valves, 6th International Congress on Acoustics, Tokyo 1968, p. F169-F172.

D.J. SMALL, Noise of high-pressure gas regulator valves, 7th International Congress on Acoustics, Budapest 1971, p. 345-348.

K.M. HYNES, The development of a low-noise constant area throttling device, ISA Transactions, 10, 4, 416-421 (1971).

W.M. JUNGOWSKI, On the pressure oscillating in a sudden enlargement of a duct section, Fluid Dynamics Transactions, edited by W. Fiszdon, Pergamon Press and PWN, 1967, p. 735-741.

W.M. JUNGOWSKI, Investigation of flow pattern, boundary conditions and oscillation mechanism in a compressible flow through sudden enlargement of a duct, The Scientific Journal, Mechanics, No 3, Warsaw Technical University Publications, 1968.

W.M. JUNGOWSKI, On the flow in a sudden enlargement of a duct, Fluid Dynamics Transactions, edited by W. Fiszdon, Pergamon Press and PWN, 4, 231-241 (1969).

K.J. WITCZAK, Choked gas outflow into a duct as the source of noise [in Polish], Dr. THESIS, Warsaw Technical University, 1975.

W.M. JUNGOWSKI, K.J. WITCZAK, Properties of an annular jet generating discrete frequency noise (to be published).

D.S. DOSANJH, J.C. Yu, A.N. ABDELHAMID, Reduction of noise from supersonic jet flows, AIAA Journal, 9, 12, 2346-2353 (1971).