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Old   May 17, 2001, 14:47
Default Request Vortex Ring Data
  #1
Adrin Gharakhani
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If you have or know someone who has DNS and/or experimental data on the evolution of a (fat) vortex ring subjected to azimuthal perturbations in its most unstable mode I would really appreciate a copy.

Thanks in advance

Adrin Gharakhani
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Old   May 18, 2001, 19:00
Default Re: Request Vortex Ring Data
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John C. Chien
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(1). How do you create a fat vortex ring? Is there any simple way to create such fat vortex ring? (2). Is it a steady-state process, or transient-state process? Is it inviscid? or viscous?
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Old   May 18, 2001, 20:25
Default Re: Request Vortex Ring Data
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Adrin Gharakhani
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Numerically, you can create anything you want; you should know better Experimentally, I'm not sure - a smoke puff coming off of a tube, whose cross-section is sinusoidally perturbed about a mean radius of a circle (to generate the initial perturbation)? I'm just guessing this is how it would be done.

As for the flow, it is definitely a transient process. A vortex ring propels under the influence of its own vorticity field. Not only that, because vorticity is perturbed initially (in its most unstable mode) the instability grows and a vortex ring that initially had no streamwise vorticity develops streamwise vorticies (3-D effects) and weak wakes behind the ring - kind of like the familiar mushroom cloud.

This is an infinite Reynolds number problem, but NOT inviscid. I'd like to get some ideas about turbulent decay of energy and enstrophy (if possible). I'd say that the characteristics of the flow will probably be independent of the actual Reynolds number, so long as it is turbulent - the instability itself is inviscid, so a DNS result would be required to capture this process accurately.

Adrin Gharakhani
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Old   May 18, 2001, 22:03
Default Re: Request Vortex Ring Data
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John C. Chien
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(1). Thank you for the information. (2). So, it is more or less an idealized problem for the study of stability issue, I guess. (3). Is there any direct application of the result from this study?
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