Exact solutions for submerged von Kármán point vortex streets cotravelling with a wave on a linear shear current
Author(s)
Crowdy, Darren
Keeler, Jack
Type
Journal Article
Abstract
New exact solutions are presented to the problem of steadily travelling water waves with vorticity wherein a submerged von Kármán point vortex street cotravels with a wave on a linear shear current. Surface tension and gravity are ignored. The work generalizes an earlier study by Crowdy & Nelson (Phys. Fluids, vol. 22, 2010, 096601) who found analytical solutions for a single point vortex row cotravelling with a water wave in a linear shear current. The main theoretical tool is the Schwarz function of the wave, and the work builds on a novel framework set out recently by Crowdy (J. Fluid Mech., vol. 954, 2022, A47). Conformal mapping theory is used to construct Schwarz functions with the requisite properties and to parametrize the waveform. A two-parameter family of solutions is found by solving a pair of nonlinear algebraic equations. This system of equations has intriguing properties: indeed, it is degenerate, which radically reduces the number of possible solutions, although the space of physically admissible equilibria is still found to be rich and diverse. For inline vortex streets, where the two vortex rows are aligned vertically, there is generally a single physically admissible solution. However, for staggered streets, where the two vortex rows are offset horizontally, certain parameter regimes produce multiple solutions. An important outcome of the work is that while only degenerate von Kármán point vortex streets can exist in an unbounded simple shear current, a broad array of such equilibria is possible in a shear current beneath a cotravelling wave on a free surface.
Date Issued
2023-08-25
Date Acceptance
2023-07-04
Citation
Journal of Fluid Mechanics, 2023, 969, pp.1-26
ISSN
0022-1120
Publisher
Cambridge University Press
Start Page
1
End Page
26
Journal / Book Title
Journal of Fluid Mechanics
Volume
969
Copyright Statement
© The Author(s), 2023. Published by Cambridge University Press. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.
License URL
Identifier
https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/exact-solutions-for-submerged-von-karman-point-vortex-streets-cotravelling-with-a-wave-on-a-linear-shear-current/8435EE947D0E876EBCD24C450B31DD72
Publication Status
Published
Date Publish Online
2023-08-10