1. Effect of Velocity Ratio on Noise Source Distribution of Coaxial Jets.
- Author
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Papamoschou, Dimitri and Rostamimonjezi, Sara
- Subjects
- *
JET plane noise , *TURBULENCE , *NOISE , *NOZZLES , *FLUID dynamics - Abstract
The noise source distribution of coaxial jets with a diameter ratio of 1.6 and variable velocity ratio is investigated with a small-aperture microphone phased array. The array design enables differentiation of noise emitted by large-scale and fine-scale turbulence structures, which have different directivities. The acoustic data are complemented by pitot surveys of the mean flow, which yield measurements of the primary and secondary cores of the jet. For zero velocity ratio (single-stream jet), the region near the nozzle emits strong high-frequency noise. Increasing the secondary-to-primary velocity ratio suppresses the near-nozzle noise and extends the location of the peak noise downstream, which increases moderately. The axial location of peak noise is approximately situated at the end of the primary core. The suppression of high-frequency noise is explained by the creation and elongation of the secondary core as the velocity ratio increases. The acoustic trends with velocity ratio are similar for small and large array observation angles from which large-scale and fine-scale turbulence noise, respectively, have been shown to radiate. However, the increase in peak noise is more pronounced for the large-scale noise. [ABSTRACT FROM AUTHOR]
- Published
- 2010
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