Title

Response to "Comment on 'Motion of a helical vortex filament in superfluid He-4 under the extrinsic form of the local induction approximation'" Phys. Fluids 26, 019101 (2014)

Authors

Authors

R. A. Van Gorder

Comments

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Abbreviated Journal Title

Phys. Fluids

Keywords

Mechanics; Physics, Fluids & Plasmas

Abstract

I agree with the authors regarding their comments on the Donnelly-Glaberson instability for such helical filaments as those obtained in my paper. I also find merit in their derivation of the quantum LIA (local induction approximation) in the manner of the LIA of Boffetta et al. However, I disagree with the primary criticisms of Hietala and Hanninen. In particular, though they suggest LIA and local nonlinear equation modes are not comparable since the former class of models contains superfluid friction parameters, note that since these parameters are small one may take them to zero and consider a qualitative comparison of the models (which is what was done in my paper). Second, while Hietala and Hanninen criticize certain assumptions made in my paper (and the paper of Shivamoggi where the model comes from) since the results break-down when Ak -> 8, note that in my paper I state that any deviations from the central axis along which the filament is aligned must be sufficiently bounded in variation. Therefore, it was already acknowledged that Ak(=vertical bar Phi(x)vertical bar) should be sufficiently bounded, precluding the Ak -> 8 case. I also show that, despite what Hietala and Hanninen claim, the dispersion relation obtained in my paper is consistent with LIA, where applicable. Finally, while Hietala and Hanninen claim that the dispersion parameter should be complex valued, I show that their dispersion relation is wrong, since it was derived incorrectly (they assume the complex modulus of the potential function is constant, yet then use this to obtain a potential function with non-constant modulus). (C) 2014 AIP Publishing LLC.

Journal Title

Physics of Fluids

Volume

26

Issue/Number

1

Publication Date

1-1-2014

Document Type

Editorial Material

Language

English

First Page

4

WOS Identifier

WOS:000331215200059

ISSN

1070-6631

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