Competition between the centrifugal and strato-rotational instabilities in the stratified Taylor-Couette flow

Junho Park, Paul Billant, Jong Jin Baik, Jaemyeong Mango Seo

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

The stably stratified Taylor-Couette flow is investigated experimentally and numerically through linear stability analysis. In the experiments, the stability threshold and flow regimes have been mapped over the ranges of outer and inner Reynolds numbers: <![CDATA[$-2000<Re-{o} and <![CDATA[$0<Re-{i}, for the radius ratio and the Brunt-Väisälä frequency . The corresponding Froude numbers and are always much smaller than unity. Depending on (or equivalently on the angular velocity ratio ), three different regimes have been identified above instability onset: a weakly non-axisymmetric mode with low azimuthal wavenumber is observed for ) while both modes are present simultaneously in the lower and upper parts of the flow for . The destabilization of these primary modes and the transition to turbulence as ), a highly non-axisymmetric mode with ( ( 0.57$]]> occurs for 840$]]> increases have been also studied. The linear stability analysis proves that the weakly non-axisymmetric mode is due to the centrifugal instability while the highly non-axisymmetric mode comes from the strato-rotational instability. These two instabilities can be clearly distinguished because of their distinct dominant azimuthal wavenumber and frequency, in agreement with the recent results of Park et al. (J. Fluid Mech., vol. 822, 2017, pp. 80-108). The stability threshold and the characteristics of the primary modes observed in the experiments are in very good agreement with the numerical predictions. Moreover, we show that the centrifugal and strato-rotational instabilities are observed simultaneously for in the lower and upper parts of the flow, respectively, because of the variations of the local Reynolds numbers along the vertical due to the salinity gradient.

Original languageEnglish
Pages (from-to)5-24
Number of pages20
JournalJournal of Fluid Mechanics
Volume840
Early online date6 Feb 2018
DOIs
Publication statusPublished - 10 Apr 2018
Externally publishedYes

Keywords

  • Key words instability
  • stratified flows
  • Taylor-Couette flow

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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