Publication: Flow/Acoustic Mechanisms in Three-Dimensional Vortices undergoing sinusoidal instabilities

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Title	Flow/Acoustic Mechanisms in Three-Dimensional Vortices undergoing sinusoidal instabilities
Authors/Editors*	Z. C. Zheng, W. Li,
Where published*	Proceedings of the 2007 ASME Mechanical Engineering Congress and Exposition
How published*	Proceedings
Year*	2007
Volume	-1
Number	-1
Pages
Publisher	Amercian Society of Mechanical Engineers
Keywords
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Abstract	It has been identified that vorticity in a vortex core directly relates to the frequency of a significant sound peak from an aircraft wake vortex pair where each of the vortices is modeled as an elliptic core Kirchhoff vortex. In three-dimensional vortices, sinusoidal instabilities at various length scales result in significant flow structure changes in these vortices, and thus influence their radiated acoustic signals. In this study, a three-dimensional vortex particle method is used to simulate the incompressible vortical flow. The flow field, in the form of vorticity, is employed as the source in the far-field acoustic calculation using a vortex sound formula that enables computation of acoustic signals radiated from an approximated incompressible flow field. Cases of vortex rings and a pair of counter-rotating vortices are studied when they are undergoing sinusoidal-wave instabilities. Both inviscid and viscous interactions are considered and effects of turbulence are simulated using sub-grid-scale models.