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Journal articles on the topic 'Vortex instability'

Author: Grafiati

Published: 6 September 2023

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1

Koshel, Konstantin V., and Eugene A. Ryzhov. "Parametric resonance in the dynamics of an elliptic vortex in a periodically strained environment." Nonlinear Processes in Geophysics 24, no. 1 (2017): 1–8. http://dx.doi.org/10.5194/npg-24-1-2017.

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Abstract. The model of an elliptic vortex evolving in a periodically strained background flow is studied in order to establish the possible unbounded regimes. Depending on the parameters of the exterior flow, there are three classical regimes of the elliptic vortex motion under constant linear deformation: (i) rotation, (ii) nutation, and (iii) infinite elongation. The phase portrait for the vortex dynamics features critical points which correspond to the stationary vortex not changing its form and orientation. We demonstrate that, given superimposed periodic oscillations to the exterior defor

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2

MacKay, R. S. "Instability of vortex streets." Dynamics and Stability of Systems 2, no. 1 (1987): 55–71. http://dx.doi.org/10.1080/02681118708806027.

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3

Acheson, D. J. "Instability of vortex leapfrogging." European Journal of Physics 21, no. 3 (2000): 269–73. http://dx.doi.org/10.1088/0143-0807/21/3/310.

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4

Marxen, Olaf, Matthias Lang, and Ulrich Rist. "Vortex formation and vortex breakup in a laminar separation bubble." Journal of Fluid Mechanics 728 (July 1, 2013): 58–90. http://dx.doi.org/10.1017/jfm.2013.222.

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AbstractThe convective primary amplification of a forced two-dimensional perturbation initiates the formation of essentially two-dimensional large-scale vortices in a laminar separation bubble. These vortices are then shed from the bubble with the forcing frequency. Immediately downstream of their formation, the vortices get distorted in the spanwise direction and quickly disintegrate into small-scale turbulence. The laminar–turbulent transition in a forced laminar separation bubble is dominated by this vortex formation and breakup process. Using numerical and experimental data, we give an in-

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5

SCHAEFFER, NATHANAËL, and STÉPHANE LE DIZÈS. "Nonlinear dynamics of the elliptic instability." Journal of Fluid Mechanics 646 (March 8, 2010): 471–80. http://dx.doi.org/10.1017/s002211200999351x.

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In this paper, we analyse by numerical simulations the nonlinear dynamics of the elliptic instability in the configurations of a single strained vortex and a system of two counter-rotating vortices. We show that although a weakly nonlinear regime associated with a limit cycle is possible, the nonlinear evolution far from the instability threshold is, in general, much more catastrophic for the vortex. In both configurations, we put forward some evidence of a universal nonlinear transition involving shear layer formation and vortex loop ejection, leading to a strong alteration and attenuation of

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6

LEWEKE, T., and C. H. K. WILLIAMSON. "Cooperative elliptic instability of a vortex pair." Journal of Fluid Mechanics 360 (April 10, 1998): 85–119. http://dx.doi.org/10.1017/s0022112097008331.

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In this paper, we investigate the three-dimensional instability of a counter-rotating vortex pair to short waves, which are of the order of the vortex core size, and less than the inter-vortex spacing. Our experiments involve detailed visualizations and velocimetry to reveal the spatial structure of the instability for a vortex pair, which is generated underwater by two rotating plates. We discover, in this work, a symmetry-breaking phase relationship between the two vortices, which we show to be consistent with a kinematic matching condition for the disturbances evolving on each vortex. In th

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7

Barnes, C. J., M. R. Visbal, and P. G. Huang. "On the effects of vertical offset and core structure in streamwise-oriented vortex–wing interactions." Journal of Fluid Mechanics 799 (June 21, 2016): 128–58. http://dx.doi.org/10.1017/jfm.2016.320.

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This article explores the three-dimensional flow structure of a streamwise-oriented vortex incident on a finite aspect-ratio wing. The vertical positioning of the incident vortex relative to the wing is shown to have a significant impact on the unsteady flow structure. A direct impingement of the streamwise vortex produces a spiralling instability in the vortex just upstream of the leading edge, reminiscent of the helical instability modes of a Batchelor vortex. A small negative vertical offset develops a more pronounced instability while a positive vertical offset removes the instability alto

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8

Mounce, A. M., S. Oh, S. Mukhopadhyay, et al. "Charge-induced vortex lattice instability." Nature Physics 7, no. 2 (2010): 125–28. http://dx.doi.org/10.1038/nphys1835.

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9

Tophøj, Laust, and Hassan Aref. "Instability of vortex pair leapfrogging." Physics of Fluids 25, no. 1 (2013): 014107. http://dx.doi.org/10.1063/1.4774333.

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10

Sukhanovskii, A., A. Evgrafova, and E. Popova. "Instability of cyclonic convective vortex." IOP Conference Series: Materials Science and Engineering 208 (June 2017): 012040. http://dx.doi.org/10.1088/1757-899x/208/1/012040.

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11

Blanco-Rodríguez, Francisco J., and Stéphane Le Dizès. "Curvature instability of a curved Batchelor vortex." Journal of Fluid Mechanics 814 (February 6, 2017): 397–415. http://dx.doi.org/10.1017/jfm.2017.34.

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In this paper, we analyse the curvature instability of a curved Batchelor vortex. We consider this short-wavelength instability when the radius of curvature of the vortex centreline is large compared with the vortex core size. In this limit, the curvature instability can be interpreted as a resonant phenomenon. It results from the resonant coupling of two Kelvin modes of the underlying Batchelor vortex with the dipolar correction induced by curvature. The condition of resonance of the two modes is analysed in detail as a function of the axial jet strength of the Batchelor vortex. In contrast t

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12

Cariteau, B., and J. B. Flór. "An experimental investigation on elliptical instability of a strongly asymmetric vortex pair in a stable density stratification." Nonlinear Processes in Geophysics 13, no. 6 (2006): 641–49. http://dx.doi.org/10.5194/npg-13-641-2006.

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Abstract. We investigate the elliptical instability of a strongly asymmetric vortex pair in a stratified fluid, generated by the acceleration and deceleration of the rotation of a single flap. The dominant parameter is the Froude number, Fr=U/(NR), based on the maximum azimuthal velocity, U, and corresponding radius, R, of the strongest vortex, i.e. the principal vortex, and buoyancy frequency N. For Fr>1, both vortices are elliptically unstable while the instability is suppressed for Fr<1. In an asymmetric vortex pair, the principal vortex is less – and the secondary vortex more – ellip

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13

Blanco-Rodríguez, Francisco J., and Stéphane Le Dizès. "Elliptic instability of a curved Batchelor vortex." Journal of Fluid Mechanics 804 (September 9, 2016): 224–47. http://dx.doi.org/10.1017/jfm.2016.533.

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The occurrence of the elliptic instability in rings and helical vortices is analysed theoretically. The framework developed by Moore & Saffman (Proc. R. Soc. Lond. A, vol. 346, 1975, pp. 413–425), where the elliptic instability is interpreted as a resonance of two Kelvin modes with a strained induced correction, is used to obtain the general stability properties of a curved and strained Batchelor vortex. Explicit expressions for the characteristics of the three main unstable modes are obtained as a function of the axial flow parameter of the Batchelor vortex. We show that vortex curvature

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14

Posa, A., and R. Broglia. "Influence by the hub vortex on the instability of the tip vortices shed by propellers with and without winglets." Physics of Fluids 34, no. 11 (2022): 115115. http://dx.doi.org/10.1063/5.0122751.

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Large-eddy simulations on a cylindrical grid consisting of 5 × 109 points are reported on both conventional and winglets propellers with and without a downstream shaft. Comparisons are focused on the influence by the hub vortex on the process of instability of the tip vortices. They demonstrate that in straight ahead conditions, this influence is actually quite limited for both propellers. The presence of the hub vortex at the wake core results in only a slight upstream shift of the instability of the tip vortices. Meanwhile, the development of the instability of the hub vortex is always delay

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15

Miyazaki, Takeshi, and Hideshi Hanazaki. "Baroclinic instability of Kirchhoff's elliptic vortex." Journal of Fluid Mechanics 261 (February 25, 1994): 253–71. http://dx.doi.org/10.1017/s0022112094000339.

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The linear instability of Kirchhoff's elliptic vortex in a vertically stratified rotating fluid is investigated using the quasi-geostrophic, f-plane approximation. Any elliptic vortex is shown to be unstable to baroclinic disturbances of azimuthal wavenumber m = 1 (bending mode) and m = 2 (elliptical deformation). The axial wavenumber of the unstable bending mode approaches Λc = 1.7046 in the limit of small ellipticity, indicating that it is a short-wave baroclinic instability. The instability occurs when the bending wave rotates around the vortex axis with angular velocity identical to the ro

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16

ALLEN, J. J., and B. AUVITY. "Interaction of a vortex ring with a piston vortex." Journal of Fluid Mechanics 465 (August 25, 2002): 353–78. http://dx.doi.org/10.1017/s0022112002001118.

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Recent studies on vortex ring generation, e.g. Rosenfeld et al. (1998), have highlighted the subtle effect of generation geometry on the final properties of rings. Experimental generation of vortex rings often involves moving a piston through a tube, resulting in a vortex ring being generated at the tube exit. A generation geometry that has been cited as a standard consists of the tube exit mounted flush with a wall, with the piston stroke ending at the tube exit, Glezer (1988). We employ this geometry to investigate the effect of the vortex that forms in front of the advancing piston (piston

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17

Ryan, Kris, Christopher J. Butler, and Gregory J. Sheard. "Stability characteristics of a counter-rotating unequal-strength Batchelor vortex pair." Journal of Fluid Mechanics 696 (March 6, 2012): 374–401. http://dx.doi.org/10.1017/jfm.2012.55.

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AbstractA Batchelor vortex represents the asymptotic solution of a trailing vortex in an aircraft wake. In this study, an unequal-strength, counter-rotating Batchelor vortex pair is employed as a model of the wake emanating from one side of an aircraft wing; this model is a direct extension of several prior investigations that have considered unequal-strength Lamb–Oseen vortices as representations of the aircraft wake problem. Both solution of the linearized Navier–Stokes equations and direct numerical simulations are employed to study the linear and nonlinear development of a vortex pair with

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18

GAUTAM, SANDEEP. "CROW INSTABILITY IN UNITARY FERMI GAS." Modern Physics Letters B 27, no. 14 (2013): 1350097. http://dx.doi.org/10.1142/s0217984913500978.

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In this paper, we investigate the initiation and subsequent evolution of Crow instability in an inhomogeneous unitary Fermi gas using zero-temperature Galilei-invariant nonlinear Schrödinger equation. Considering a cigar-shaped unitary Fermi gas, we generate the vortex–antivortex pair either by phase-imprinting or by moving a Gaussian obstacle potential. We observe that the Crow instability in a unitary Fermi gas leads to the decay of the vortex–antivortex pair into multiple vortex rings and ultimately into sound waves.

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19

Liu, Zhi Rong, Jun Wei Wang, and Rui Zhu. "Fluid Experimental Research on Dual-Vortex Interaction Instability." Advanced Materials Research 459 (January 2012): 195–98. http://dx.doi.org/10.4028/www.scientific.net/amr.459.195.

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A series of dual-vortex fulid visualization and interaction instability experiments are undertaken with PIV (Particle Image Velocimetry) system under various experimental parameters sets. The motion characteristics and the circulation-time curves of the dual-vortex are presented through PIV processing and analysis. The dual-vortex distance b=50mm, main wingtip angle α1=10° & side wingtip angle α2=8° are optimum experimental parameters for vortices dissipation, the most vortex strength is reduced by 30%-40%

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20

Ford, Rupert. "The instability of an axisymmetric vortex with monotonic potential vorticity in rotating shallow water." Journal of Fluid Mechanics 280 (December 10, 1994): 303–34. http://dx.doi.org/10.1017/s0022112094002946.

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The stability of an axisymmetric vortex with a single radial discontinuity in potential vorticity is investigated in rotating shallow water. It is shown analytically that the vortex is always unstable, using the WKBJ method for instabilities with large azimuthal mode number. The analysis reveals that the instability is of mixed type, involving the interaction of a Rossby wave on the boundary of the vortex and a gravity wave beyond the sonic radius. Numerically, it is demonstrated that the growth rate of the instability is generally small, except when the potential vorticity in the vortex is th

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21

BILLANT, P., A. DELONCLE, J. M. CHOMAZ, and P. OTHEGUY. "Zigzag instability of vortex pairs in stratified and rotating fluids. Part 2. Analytical and numerical analyses." Journal of Fluid Mechanics 660 (July 21, 2010): 396–429. http://dx.doi.org/10.1017/s002211201000282x.

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The three-dimensional stability of vertical vortex pairs in stratified and rotating fluids is investigated using the analytical approach established in Part 1 and the predictions are compared to the results of previous direct numerical stability analyses for pairs of co-rotating equal-strength Lamb–Oseen vortices and to new numerical analyses for equal-strength counter-rotating vortex pairs. A very good agreement between theoretical and numerical results is generally found, thereby providing a comprehensive description of the zigzag instability. Co-rotating and counter-rotating vortex pairs ar

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22

LIN, H. C., and W. M. YANG. "LOWEST STABILITY BOUNDARY ON FLOW OF CONCENTRIC ROTATING CYLINDERS." International Journal of Bifurcation and Chaos 20, no. 05 (2010): 1527–32. http://dx.doi.org/10.1142/s0218127410026678.

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In this study, we numerically investigate the lowest instability boundary of nonaxisymmetric Taylor vortex flow (TVF) for different axial wavenumbers. The variation in the axial wavenumber of a supercritical TVF can affect the instability of the flow, because the wavelength of a Taylor vortex is constant only when the flow is axisymmetrical. When the nonaxisymmetric TVF is transformed to a wavy vortex flow (WVF), the instability boundary is changed with the variation in the axial wavenumber. We carry out an instability analysis of the nonaxisymmetric TVF between two concentric rotating cylinde

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23

Kennan, Sean C., and Pierre J. Flament. "Observations of a Tropical Instability Vortex*." Journal of Physical Oceanography 30, no. 9 (2000): 2277–301. http://dx.doi.org/10.1175/1520-0485(2000)030<2277:ooativ>2.0.co;2.

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24

Wang, Hongyun. "Short Wave Instability on Vortex Filaments." Physical Review Letters 80, no. 21 (1998): 4665–68. http://dx.doi.org/10.1103/physrevlett.80.4665.

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25

Meunier, Patrice, and Thomas Leweke. "Three-dimensional instability during vortex merging." Physics of Fluids 13, no. 10 (2001): 2747–50. http://dx.doi.org/10.1063/1.1399033.

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26

FLORYAN, J. M. "Vortex instability in a divergingconverging channel." Journal of Fluid Mechanics 482 (May 10, 2003): 17–50. http://dx.doi.org/10.1017/s0022112003003987.

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27

FUKUMOTO, YASUHIDE, and YUJI HATTORI. "Curvature instability of a vortex ring." Journal of Fluid Mechanics 526 (March 10, 2005): 77–115. http://dx.doi.org/10.1017/s0022112004002678.

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28

Gitterman, M., B. Ya Shapiro, I. Shapiro, B. Kalisky, A. Shaulov, and Y. Yeshurun. "Oscillating flux instability in vortex matter." Physica C: Superconductivity 460-462 (September 2007): 1247–48. http://dx.doi.org/10.1016/j.physc.2007.04.191.

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29

Pozrikidis, C. "The nonlinear instability of Hill's vortex." Journal of Fluid Mechanics 168, no. -1 (1986): 337. http://dx.doi.org/10.1017/s002211208600040x.

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30

Richardson, G. "Instability of a superconducting line vortex." Physica D: Nonlinear Phenomena 110, no. 1-2 (1997): 139–53. http://dx.doi.org/10.1016/s0167-2789(97)00119-x.

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31

Janu, Z., R. Tichy, and V. Plechacek. "Instability in vortex system in HTSC." IEEE Transactions on Magnetics 30, no. 2 (1994): 1226–28. http://dx.doi.org/10.1109/20.312223.

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32

Asselin, Daniel J., and C. H. K. Williamson. "Influence of a wall on the three-dimensional dynamics of a vortex pair." Journal of Fluid Mechanics 817 (March 20, 2017): 339–73. http://dx.doi.org/10.1017/jfm.2017.114.

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In this paper, we are interested in perturbed vortices under the influence of a wall or ground plane. Such flows have relevance to aircraft wakes in ground effect, to ship hull junction flows, to fundamental studies of turbulent structures close to a ground plane and to vortex generator flows, among others. In particular, we study the vortex dynamics of a descending vortex pair, which is unstable to a long-wave instability (Crow, AIAA J., vol. 8 (12), 1970, pp. 2172–2179), as it interacts with a horizontal ground plane. Flow separation on the wall generates opposite-sign secondary vortices whi

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33

CANALS, MIGUEL, and GENO PAWLAK. "Three-dimensional vortex dynamics in oscillatory flow separation." Journal of Fluid Mechanics 674 (March 23, 2011): 408–32. http://dx.doi.org/10.1017/s0022112011000012.

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The dynamics of coherent columnar vortices and their interactions in an oscillatory flow past an obstacle are examined experimentally. The main focus is on the low Keulegan–Carpenter number range (0.2 < KC < 2), where KC is the ratio between the fluid particle excursion during half an oscillation cycle and the obstacle size, and for moderate Reynolds numbers (700 < Rev < 7500). For this parameter range, a periodic unidirectional vortex pair ejection regime is observed, in which the direction of vortex propagation is set by the initial conditions of the oscillations. These vortex pa

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34

Olsthoorn, Jason, and Stuart B. Dalziel. "Three-dimensional visualization of the interaction of a vortex ring with a stratified interface." Journal of Fluid Mechanics 820 (May 10, 2017): 549–79. http://dx.doi.org/10.1017/jfm.2017.215.

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The study of vortex-ring-induced stratified mixing has long played a key role in understanding externally forced stratified turbulent mixing. While several studies have investigated the dynamical evolution of such a system, this study presents an experimental investigation of the mechanical evolution of these vortex rings, including the stratification-modified three-dimensional instability. The aim of this paper is to understand how vortex rings induce mixing of the density field. We begin with a discussion of the Reynolds and Richardson number dependence of the vortex-ring interaction using t

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35

BOULANGER, NICOLAS, PATRICE MEUNIER, and STÉPHANE LE DIZÈS. "Tilt-induced instability of a stratified vortex." Journal of Fluid Mechanics 596 (January 17, 2008): 1–20. http://dx.doi.org/10.1017/s0022112007009263.

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This experimental and theoretical study considers the dynamics and the instability of a Lamb–Oseen vortex in a stably stratified fluid. In a companion paper, it was shown that tilting the vortex axis with respect to the direction of stratification induces the formation of a rim of strong axial flow near a critical radius when the Froude number of the vortex is larger than one.Here, we demonstrate that this tilt-induced flow is responsible for a three-dimensional instability. We show that the instability results from a shear instability of the basic axial flow in the critical-layer region. The

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36

ORLANDI, P., and G. F. CARNEVALE. "Evolution of isolated vortices in a rotating fluid of finite depth." Journal of Fluid Mechanics 381 (February 25, 1999): 239–69. http://dx.doi.org/10.1017/s0022112098003693.

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Laboratory experiments have shown that monopolar isolated vortices in a rotating flow undergo instabilities that result in the formation of multipolar vortex states such as dipoles and tripoles. In some cases the instability is entirely two-dimensional, with the vortices taking the form of vortex columns aligned along the direction of the ambient rotation at all times. In other cases, the vortex first passes through a highly turbulent three-dimensional state before eventually reorganizing into vortex columns. Through a series of three-dimensional numerical simulations, the roles that centrifug

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37

Maslowe, Sherwin A. "Linear instability of a perturbed Lamb–Oseen vortex." Fluid Dynamics Research 54, no. 1 (2022): 015513. http://dx.doi.org/10.1088/1873-7005/ac522d.

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Abstract This paper presents an investigation of the stability of a vortex with azimuthal velocity profile V ˉ = 1 − 1 − ε r 2 e − r 2 / r . When ε = 0, the Lamb–Oseen vortex model is recovered. Although the Lamb–Oseen vortex supports propagating waves known as Kelvin waves, the flow is stable according to Rayleigh’s circulation criterion. In this paper, on the other hand, the modified vortex profile admits linearly unstable disturbances for ε > 0 and we investigate their characteristics. These may be either axisymmetric or non-axisymmetric, but we find that the axisymmetric perturbations h

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38

Quaranta, Hugo Umberto, Hadrien Bolnot, and Thomas Leweke. "Long-wave instability of a helical vortex." Journal of Fluid Mechanics 780 (September 9, 2015): 687–716. http://dx.doi.org/10.1017/jfm.2015.479.

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We investigate the instability of a single helical vortex filament of small pitch with respect to displacement perturbations whose wavelength is large compared to the vortex core size. We first revisit previous theoretical analyses concerning infinite Rankine vortices, and consider in addition the more realistic case of vortices with Gausssian vorticity distributions and axial core flow. We show that the various instability modes are related to the local pairing of successive helix turns through mutual induction, and that the growth rate curve can be qualitatively and quantitatively predicted

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39

Abdullah, M. Z., Z. Husain, and S. M. Fraser. "Application of Deswirl Device in Cyclone Dust Separator." ASEAN Journal on Science and Technology for Development 20, no. 3&4 (2017): 203–16. http://dx.doi.org/10.29037/ajstd.354.

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The experimental investigations of the vortex flow inside the vortex finder (outlet duct) of the cyclone dust separator have been carried out. Preliminary study from the visualization experiment has been performed and discovered vortex instability inside the conventional vortex finder. In order to minimize the instabilities, the streamlined entry shape was inserted at the vortex finder entrance and the results showed remarkable improvement of the vortex flow instability inside the vortex finder. The velocity measurements of two main components of velocity were performed using a laser-Doppler a

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40

Men, Hongyuan, Xinliang Li, and Hongwei Liu. "Direct numerical simulations of hypersonic boundary layer transition over a hypersonic transition research vehicle model lifting body at different angles of attack." Physics of Fluids 35, no. 4 (2023): 044111. http://dx.doi.org/10.1063/5.0146651.

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This paper performs direct numerical simulations of hypersonic boundary layer transition over a Hypersonic Transition Research Vehicle (HyTRV) model lifting body designed by the China Aerodynamic Research and Development Center. Transitions are simulated at four angles of attack: 0°, 3°, 5°, and 7°. The free-stream Mach number is 6, and the unit Reynolds number is 107 m−1. Four distinct transitional regions are identified: the shoulder cross-flow and vortex region and the shoulder vortex region on the leeward side, the windward vortex region and the windward cross-flow region on the windward s

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41

Zhao, Wu, Wei Tao Jia, Quan Bin Zhang, and Zhan Qi Hu. "Stable Equilibrium Analysis and Simulation Considering Effect of Cutting Fluid Inside and Outside BTA Boring Bar." Advanced Materials Research 902 (February 2014): 129–34. http://dx.doi.org/10.4028/www.scientific.net/amr.902.129.

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This paper is proposed to reveal the stable equilibrium on the boring bar during heavy-duty deep-hole boring trepanning processing environment, including three conditions considering vortex instability caused by outside cutting fluid, perturbation instability caused by inside cutting fluid and synthesized instability accompanied both inner and outer cutting fluid, respectively. Every position of stable equilibrium and formula of rotation speed in instability are obtained. It is shown that the system instability induced by no matter how different situations, is resulted from half frequency vort

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42

Kunchur, Milind N., and James M. Knight. "Hot-Electron Instability in Superconductors." Modern Physics Letters B 17, no. 10n12 (2003): 549–58. http://dx.doi.org/10.1142/s0217984903005573.

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High flux velocities in a superconductor can distort the quasiparticle distribution function and elevate the electronic temperature. Close to T c , a non-thermal distribution function shrinks the vortex core producing the well-known Larkin-Ovchinnikov flux instability. In the present work we consider the opposite limit of low temperatures, where electron-electron scattering is more rapid than electron-phonon, resulting in an electronic temperature rise with a thermal-like distribution function. This produces a different kind of flux instability, due to a reduction in condensate and expansion o

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43

CROUCH, J. D. "Instability and transient growth for two trailing-vortex pairs." Journal of Fluid Mechanics 350 (November 10, 1997): 311–30. http://dx.doi.org/10.1017/s0022112097007040.

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The stability of two vortex pairs is analysed as a model for the vortex system generated by an aircraft in flaps-down configuration. The co-rotating vortices on the starboard and port sides tumble about one another as they propagate downward. This results in a time-periodic basic state for the stability analysis. The dynamics and instability of the trailing vortices are modelled using thin vortex filaments. Stability equations are derived by matching the induced velocities from Biot–Savart integrals with kinematic equations obtained by temporal differentiation of the vortex position vectors. T

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44

Pozrikidis, C., and J. J. L. Higdon. "Nonlinear Kelvin–Helmholtz instability of a finite vortex layer." Journal of Fluid Mechanics 157 (August 1985): 225–63. http://dx.doi.org/10.1017/s0022112085002361.

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The nonlinear growth of periodic disturbances on a finite vortex layer is examined. Under the assumption of constant vorticity, the evolution of the layer may be analysed by following the contour of the vortex region. A numerical procedure is introduced which leads to higher-order accuracy than previous methods with negligible increase in computational effort. The response of the vortex layer is studied as a function of layer thickness and the amplitude and form of the initial disturbance. For small initial disturbances, all unstable layers form a large rotating vortex core of nearly elliptica

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45

Thomas, P. J., and D. Auerbach. "The observation of the simultaneous development of a long- and a short-wave instability mode on a vortex pair." Journal of Fluid Mechanics 265 (April 25, 1994): 289–302. http://dx.doi.org/10.1017/s0022112094000844.

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Experiments on the stability of vortex pairs are described. The vortices (ratio of length to core diameter L/c of up to 300) were generated at the edge of a flat plate rotating about a horizontal axis in water. The vortex pairs were found to be unstable, displaying two distinct modes of instability. For the first time, as far as it is known to the authors, a long-wave as well as a short-wave mode of instability were observed to develop simultaneously on such a vortex pair. Experiments involving single vortices show that these do not develop any instability whatsoever. The wavelengths of the de

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46

KLOOSTERZIEL, R. C., G. F. CARNEVALE, and P. ORLANDI. "Inertial instability in rotating and stratified fluids: barotropic vortices." Journal of Fluid Mechanics 583 (July 4, 2007): 379–412. http://dx.doi.org/10.1017/s0022112007006325.

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The unfolding of inertial instability in intially barotropic vortices in a uniformly rotating and stratified fluid is studied through numerical simulations. The vortex dynamics during the instability is examined in detail. We demonstrate that the instability is stabilized via redistribution of angular momentum in a way that produces a new equilibrated barotropic vortex with a stable velocity profile. Based on extrapolations from the results of a series of simulations in which the Reynolds number and strength of stratification are varied, we arrive at a construction based on angular momentum mi

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ALLEN, J. J., and T. NAITOH. "Scaling and instability of a junction vortex." Journal of Fluid Mechanics 574 (February 15, 2007): 1–23. http://dx.doi.org/10.1017/s0022112006003879.

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This paper details experiments in the region where an impulsively started moving wall slides under a stationary wall. The experiments were conducted over a Reynolds number range of ReΓ=5×102–5×105. The length scale for the Reynolds number is defined as the distance the wall has moved from rest and increases during an experiment. Experiments show that for ReΓ>103 a vortex forms close to the junction where the moving wall meets the stationary one. The data shows that while the vortical structure is small, in relation to the fixed-apparatus length scale, the size of the vortex normalized with

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Yim, Eunok, and Paul Billant. "Analogies and differences between the stability of an isolated pancake vortex and a columnar vortex in stratified fluid." Journal of Fluid Mechanics 796 (May 11, 2016): 732–66. http://dx.doi.org/10.1017/jfm.2016.248.

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In order to understand the dynamics of pancake shaped vortices in stably stratified fluids, we perform a linear stability analysis of an axisymmetric vortex with Gaussian angular velocity in both the radial and axial directions with an aspect ratio of ${\it\alpha}$. The results are compared to those for a columnar vortex (${\it\alpha}=\infty$) in order to identify the instabilities. Centrifugal instability occurs when $\mathscr{R}>c(m)$ where $\mathscr{R}=ReF_{h}^{2}$ is the buoyancy Reynolds number, $F_{h}$ the Froude number, $Re$ the Reynolds number and $c(m)$ a constant which differs for

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Stout, Eric, and Fazle Hussain. "External turbulence-induced axial flow and instability in a vortex." Journal of Fluid Mechanics 793 (March 16, 2016): 353–79. http://dx.doi.org/10.1017/jfm.2016.123.

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External turbulence-induced axial flow in an incompressible, normal-mode stable Lamb–Oseen (two-dimensional) vortex column is studied via direct numerical simulations of the Navier–Stokes equations. Azimuthally oriented vorticity filaments, formed from external turbulence, advect radially towards or away from the vortex axis (depending on the filament’s swirl direction), resulting in a net induced axial flow in the vortex core; axial flow increases with increasing vortex Reynolds number ($Re=$ vortex circulation/viscosity). This contrasts the viscous mechanism for axial flow generation downstr

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Shcherbakov, S. "A COMPLETE DESCRIPTION OF THE MECHANICS OF TURBULENCE IN A MOVING FLUID." PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. SERIES: NUCLEAR AND REACTOR CONSTANTS 2020, no. 3 (2020): 97–109. http://dx.doi.org/10.55176/2414-1038-2020-3-97-109.

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The conditions and mechanisms of events in a moving fluid are analyzed, leading to the apparent disorder of unsteady flow, known as turbulence. The method of analysis is the use of different forms of equations of motion and transfer of characteristics, the selection of stable formations in the flow structure and a description of the interaction between them. The non-trivial results of previous works are used. The transfer and transformation of disturbances of a vortex distributed in the flow is analyzed, the conditions under which insulated tubes with a helical flow appear inside the shear flo

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