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On the limitations of the complex wave velocity for the heterogeneous swirling flows

  • Prakash Shanmugam ORCID logo EMAIL logo
Published/Copyright: September 25, 2023

Abstract

The hydrodynamic instability of variable density swirling flows under gravity between two infinite coaxial cylinders is investigated for axisymmetric disturbances. It is shown that the complex wave velocity of any arbitrary unstable axisymmetric mode must lie within the semi-elliptical region whose minor axis depends on the density stratification parameter J(r). The stabilizing effect of density stratification is shown by reducing the semi-circular instability region of [G. K. Batchelor and A. E. Gill, “Analysis of the stability of axisymmetric jets,” J. Fluid Mech., vol. 14, p. 529, 1962]. Furthermore, we have obtained two parabolic instability regions which intersect and reduce the semi-elliptical instability region for density-stratified flows. These parabolic instability regions are uniformly valid for both variable density and density homogeneous flows also.

MSC 2010: 76E05

Corresponding author: Prakash Shanmugam, Department of Mathematics, SAS, Vellore Institute of Technology - AP, Amaravathi, Andhra Pradesh, 522237 India, E-mail:

Acknowledgments

Author thank Prof. M. Subbiah for discussions which forms the basis of this work.

  1. Research ethics: Not applicable.

  2. Author contributions: Entire work is done by single author Prakash Shanmugam.

  3. Competing interests: Author declares that he has no conflict of interest in this work.

  4. Research funding: The author acknowledges with thanks to the Council of Scientific and Industrial Research (CSIR), India for financial support under the grant 09/559(0134)/2019-EMR-I.

  5. Data availability: No data is used in this research.

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Received: 2023-07-28
Accepted: 2023-09-01
Published Online: 2023-09-25
Published in Print: 2023-11-27

© 2023 Walter de Gruyter GmbH, Berlin/Boston

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