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Axisymmetric flows on the torus geometry

Busuioc, Sergiu; Kusumaatmaja, H.; Ambruş, Victor E.

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Sergiu Busuioc

Victor E. Ambruş


We present a series of analytically solvable axisymmetric flows on the torus geometry. For the single-component flows, we describe the propagation of sound waves for perfect fluids, as well as the viscous damping of shear and longitudinal waves for isothermal and thermal fluids. Unlike the case of planar geometry, the non-uniform curvature on a torus necessitates a distinct spectrum of eigenfrequencies and their corresponding basis functions. This has several interesting consequences, including breaking the degeneracy between even and odd modes, a lack of periodicity even in the flows of perfect fluids and the loss of Galilean invariance for flows with velocity components in the poloidal direction. For the multi-component flows, we study the equilibrium configurations and relaxation dynamics of axisymmetric fluid stripes, described using the Cahn–Hilliard equation. We find a second-order phase transition in the equilibrium location of the stripe as a function of its area ΔA . This phase transition leads to a complex dependence of the Laplace pressure on ΔA . We also derive the underdamped oscillatory dynamics as the stripes approach equilibrium. Furthermore, relaxing the assumption of axial symmetry, we derive the conditions under which the stripes become unstable. In all cases, the analytical results are confirmed numerically using a finite-difference Navier–Stokes solver.


Busuioc, S., Kusumaatmaja, H., & Ambruş, V. E. (2020). Axisymmetric flows on the torus geometry. Journal of Fluid Mechanics, 901, Article A9.

Journal Article Type Article
Online Publication Date Aug 24, 2020
Publication Date Oct 25, 2020
Deposit Date Sep 10, 2020
Publicly Available Date Feb 24, 2021
Journal Journal of Fluid Mechanics
Print ISSN 0022-1120
Electronic ISSN 1469-7645
Publisher Cambridge University Press
Peer Reviewed Peer Reviewed
Volume 901
Article Number A9


Accepted Journal Article (7.5 Mb)

Copyright Statement
This material has been published in <br /> Busuioc, Sergiu, Kusumaatmaja, H. &amp; Ambruş, Victor E. (2020). Axisymmetric flows on the torus geometry. Journal of Fluid Mechanics 901: A9. This version is free to view and download for personal use only. Not for re-distribution, re-sale or use in derivative works. &copy; The Author(s), 2020. Published by Cambridge University Press.

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