Impact of centrifugal buoyancy on strato-rotational instability

Lopez, Juan M.; Marqués, Francisco

doi:10.1017/jfm.2020.135

Cited by 9 publications

(22 citation statements)

References 39 publications

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“…The (strobed) position of the defect at mid-height remains constant during the regular phase, while it experiences a jump during the irregular phase; this jump coincides with -symmetry breaking. This behaviour is a ‘snapping’ of the defect; it was also observed in very wide-gap stratified Taylor–Couette flow (Lopez & Marques 2020), in which both curvature and centrifugal buoyancy effects were much stronger than in the present problem. There, the ‘snapping’ was related to the detuning of the frequencies associated with the centrifugal instabilities near the endwalls.…”

Section: Three-dimensional Instability Of the Basic Statesupporting

confidence: 74%

“…This was a very different regime to that typically studied for stratified Taylor–Couette flow. In Lopez & Marques (2020), we reproduced these results and found that endwall effects and centrifugal buoyancy were critical ingredients for understanding the observed onset of instability and the subsequent dynamics. The rotation of the inner cylinder induces radial forces: the denser fluid is centrifuged outwards, while the lighter fluid is centrifuged inwards.…”

Section: Introductionmentioning

confidence: 52%

“…In similar stratified Taylor–Couette flows with smaller radius ratio, , and stronger stratification (Flór et al. 2018; Lopez & Marques 2020), the corner vortices emit spiral waves with small inclination towards the interior. The frequencies of these spiral waves emitted from the top and bottom endwalls are slightly different due to the imperfect symmetry, although the frequencies lock near the bifurcation point resulting is single frequency periodic flow.…”

Section: Discussionmentioning

confidence: 99%

“…In the small experiments (Flór et al. 2018) and numerical simulations (Lopez & Marques 2020), centrifugal buoyancy leads to the lower corner losing stability at a lower than the top corner, and these localized perturbations have slightly different frequencies. However, in the present medium study, it appears that due to viscous effects together with the small value of (quantifying the strength of the centrifugal buoyancy), the two instability wave frequencies lock and the whole flow is a single frequency periodic flow (a rotating wave) over a wide range of , from onset at up to .…”

Section: Discussionmentioning

confidence: 99%

“…We shall also fix their ratio such that . This is motivated by several reasons; this is the value of used in our very wide-gap study (Lopez & Marques 2020) that reproduced the experimental observations of Flór et al. (2018).…”

Section: Governing Equationsmentioning

confidence: 90%

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Stratified Taylor–Couette flow: nonlinear dynamics

Lopez

Marqués

2021

J. Fluid Mech.

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A series of experiments on stratified Taylor–Couette flow in short aspect ratio wide-gap annuli found an intriguing and not-well-understood dynamics: nonlinear coherent structures appearing and disappearing periodically, along with density layering reminiscent of staircase profiles. A detailed numerical study is presented of the nonlinear dynamics near onset of instability in this setting, which explains most of the characteristics found in the experiments. The simulations show that centrifugal instability of the boundary layer on the inner rotating cylinder produces jets of angular momentum forming Taylor cells that are compressed axially due to the strong stratification. These cells are not axisymmetric from the onset, but are in fact two sets of Taylor cells displaced axially that meet in localized azimuthal defect regions where the cells are patched together; the whole structure is a rotating wave with azimuthal wavenumber $m=1$ . The presence of endwalls in this short aspect ratio annulus is critical for the understanding of the dynamics. Their impact cannot be accounted for in idealized axially periodic models. Another key ingredient is the role played by the symmetries of the system. Although the axial reflection symmetry is weakly broken by centrifugal buoyancy effects, following instability there are various branches of solutions corresponding to the different ways the system's symmetries may be broken.

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Section: Three-dimensional Instability Of the Basic Statesupporting

confidence: 74%

Section: Introductionmentioning

confidence: 52%