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Vortex ring instability and its soundThis work carries earlier finite-difference calculations of the Widnall instability of vortex rings into the late non-linear stage. Plots of energy in azimuthal Fourier modes indicate that low-order modes dominate at large times; their structure and dynamics remain unexplored, however. An attempt was made to calculate the acoustic signal using the theory of Mohring (1978), valid for unbounded flow. This theory shows that only low-order azimuthal modes contribute to the sound. As a check on the effects of axial periodicity and a slip wall at large radius imposed by the numerical scheme, the acoustic integrals were also computed in a truncated region. Half of the terms contributing to the sound have large differences between the two regions, and the results are therefore unreliable. The error is less severe for a contribution involving only the m = 2 mode, and its low frequency is consistent with a free elliptic bending wave on a thin ring.
Document ID
19950014631
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Verzicco, R. (Rome Univ. Italy)
Shariff, K. (NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
September 6, 2013
Publication Date
December 1, 1994
Publication Information
Publication: Stanford Univ., Studying Turbulence Using Numerical Simulation Databases. 5: Proceedings of the 1994 Summer Program
Subject Category
Fluid Mechanics And Heat Transfer
Accession Number
95N21048
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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