NASA Technical Reports Server (NTRS) : Numerical pdf

NASA Technical Reports Server (NTRS) : Numerical

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An imperfectly expanded supersonic jet, invariably, radiates both broadband noise and discrete frequency sound called screech tones. Screech tones are known to be generated by a feedback loop driven by the large scale instability waves of the jet flow. Inside the jet plume is a quasi-periodic shock cell structure. The interaction of the instability waves and the shock cell structure, as the former propagates through the latter, is responsible for the generation of the tones. Presently, there are formulas that can predict the tone frequency fairly accurately. However, there is no known way to predict the screech tone intensity. In this work, the screech phenomenon of an axisymmetric jet at low supersonic Mach number is reproduced by numerical simulation. The computed mean velocity profiles and the shock cell pressure distribution of the jet are found to be in good agreement with experimental measurements. The same is true with the simulated screech frequency.

Calculated screech tone intensity and directivity at selected jet Mach number are reported in this paper. The present results demonstrate that numerical simulation using computational aeroacoustics methods offers not only a reliable way to determine the screech tone intensity and directivity but also an opportunity to study the physics and detailed mechanisms of the phenomenon by an entirely new approach

• Creator/s: NASA Technical Reports Server (NTRS
• Date: 1/1/1998
• Year: 1998
• Book Topics/Themes: NASA Technical Reports Server (NTRS), COMPUTERIZED SIMULATION, NUMERICAL FLOW VISUALIZATION, SUPERSONIC JET FLOW, SCREECH TONES, MACH NUMBER, AEROACOUSTICS, AXIAL FLOW, AXIAL COMPRESSION LOADS, NUMERICAL ANALYSIS, VELOCITY DISTRIBUTION, SUPERSONIC SPEED, SOUND WAVES, PRESSURE DISTRIBUTION, NOISE (SOUND), FREQUENCIES, BROADBAND, Shen, Hao, Tam, Christopher K. W

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