Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Sound generation by vortex pairing in subsonic axisymmetric jets
AU - Jiang, X
AU - Avital, E J
AU - Luo, K H
AU - Jiang, Xi
PY - 2004/2
Y1 - 2004/2
N2 - Direct numerical simulation (DNS) and an acoustic analogy are used to investigate the sound generation by vortex pairing in idealized subsonic axisymmetric jets. The detailed sound source structure is provided by the DNS. The acoustic analogy is based on solving the nonlinearized Lilley's third-order wave equation in the time-space domain. A numerical algorithm for solving Lilley's equation is developed, in which the sound field is simulated simultaneously with the source field calculation. The computational domain includes both the near field and a portion of the acoustic far field. Effects of a coaxial secondary jet stream and the jet-to-ambient temperature ratio on the sound generation from an axisymmetric jet are investigated. It is shown that the sound source has a long axial distribution in the streamwise direction with the strongest source located near the end of the jet potential core where vortex pairing/merging occurs, and the radiated sound field is highly directive. It is also found that the secondary jet stream reduces the sound source size; therefore, the sound radiation from the coaxial jets is lower than that from the single jet. The hot jet simulation shows that increasing the jet-to-ambient temperature ratio leads to a smaller and weaker sound source, but does not lead to a weaker sound field. For the sound field a reasonable agreement is observed between the predictions from the axisymmetric Lilley's equation and the DNS results.
AB - Direct numerical simulation (DNS) and an acoustic analogy are used to investigate the sound generation by vortex pairing in idealized subsonic axisymmetric jets. The detailed sound source structure is provided by the DNS. The acoustic analogy is based on solving the nonlinearized Lilley's third-order wave equation in the time-space domain. A numerical algorithm for solving Lilley's equation is developed, in which the sound field is simulated simultaneously with the source field calculation. The computational domain includes both the near field and a portion of the acoustic far field. Effects of a coaxial secondary jet stream and the jet-to-ambient temperature ratio on the sound generation from an axisymmetric jet are investigated. It is shown that the sound source has a long axial distribution in the streamwise direction with the strongest source located near the end of the jet potential core where vortex pairing/merging occurs, and the radiated sound field is highly directive. It is also found that the secondary jet stream reduces the sound source size; therefore, the sound radiation from the coaxial jets is lower than that from the single jet. The hot jet simulation shows that increasing the jet-to-ambient temperature ratio leads to a smaller and weaker sound source, but does not lead to a weaker sound field. For the sound field a reasonable agreement is observed between the predictions from the axisymmetric Lilley's equation and the DNS results.
KW - SUPERSONIC COAXIAL JETS
KW - NOISE
KW - SCHEMES
M3 - Journal article
VL - 42
SP - 241
EP - 248
JO - AIAA Journal
JF - AIAA Journal
SN - 0001-1452
IS - 2
ER -