Nonlinear centrifugal instabilities in curved free shear layers

Omar Es-Sahli, Adrian Sescu, Mohammed Afsar

Research output: Contribution to conferencePaper

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Abstract

Curved free shear layers exist in many engineering problems involving complex flow geometries, such as the backward facing step flow, flows with wall injection, the flow inside side-dump combustors, or flows generated by vertical axis wind turbines, among others. Most of the studies involving centrifugal instabilities have been focused on wall flows where Taylor instabilities between two rotating concentric cylinders or Görtler vortices in bound- ary layers resulting from the imbalance between centrifugal effects and radial pressure gradients, are generated. Curved free shear layers, however, did not receive sufficient at- tention. An examination of the stability characteristics and the flow structures associated with curved free shear flows should provide a better understanding of these complex flow problems. In this work, we study the development of Görtler vortices inside a curved shear layer in both the incompressible and compressible regimes using a numerical solution to a parabolized form of the Navier-Stokes equations, in the assumption that the stream- wise wavenumber associated with the vortex flow is much smaller than the crossstream wavenumbers. Various results consisting of contour plots of centrifugal instabilites in cross- flow planes, and energy and streak amplitude distributions along the streamwise direction are reported and discussed. In addition, we conduct a biglobal stability analysis to study the growth rates and the eigenmodes associated with these flows.
Original languageEnglish
Number of pages19
Publication statusPublished - 10 Jan 2020
EventAmerican Institute of Aeronautics and Astronautics (AIAA) SciTech Forum
- Hyatt Regency Orlando , Orlando, United States
Duration: 6 Jan 202010 Jan 2020
https://www.aiaa.org/SciTech

Conference

ConferenceAmerican Institute of Aeronautics and Astronautics (AIAA) SciTech Forum
Abbreviated titleSciTech 2020
CountryUnited States
CityOrlando
Period6/01/2010/01/20
Internet address

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shear layers
vortices
dump combustors
flow geometry
wall flow
concentric cylinders
backward facing steps
cross flow
wind turbines
Taylor instability
pressure gradients
shear flow
Navier-Stokes equation
boundary layers
examination
plots
engineering
injection

Keywords

  • Gortler vortices
  • Navier Stokes equations
  • stability analysis

Cite this

Es-Sahli, O., Sescu, A., & Afsar, M. (2020). Nonlinear centrifugal instabilities in curved free shear layers. Paper presented at American Institute of Aeronautics and Astronautics (AIAA) SciTech Forum
, Orlando, United States.
Es-Sahli, Omar ; Sescu, Adrian ; Afsar, Mohammed. / Nonlinear centrifugal instabilities in curved free shear layers. Paper presented at American Institute of Aeronautics and Astronautics (AIAA) SciTech Forum
, Orlando, United States.19 p.
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Es-Sahli, O, Sescu, A & Afsar, M 2020, 'Nonlinear centrifugal instabilities in curved free shear layers', Paper presented at American Institute of Aeronautics and Astronautics (AIAA) SciTech Forum
, Orlando, United States, 6/01/20 - 10/01/20.

Nonlinear centrifugal instabilities in curved free shear layers. / Es-Sahli, Omar; Sescu, Adrian; Afsar, Mohammed.

2020. Paper presented at American Institute of Aeronautics and Astronautics (AIAA) SciTech Forum
, Orlando, United States.

Research output: Contribution to conferencePaper

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T1 - Nonlinear centrifugal instabilities in curved free shear layers

AU - Es-Sahli, Omar

AU - Sescu, Adrian

AU - Afsar, Mohammed

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N2 - Curved free shear layers exist in many engineering problems involving complex flow geometries, such as the backward facing step flow, flows with wall injection, the flow inside side-dump combustors, or flows generated by vertical axis wind turbines, among others. Most of the studies involving centrifugal instabilities have been focused on wall flows where Taylor instabilities between two rotating concentric cylinders or Görtler vortices in bound- ary layers resulting from the imbalance between centrifugal effects and radial pressure gradients, are generated. Curved free shear layers, however, did not receive sufficient at- tention. An examination of the stability characteristics and the flow structures associated with curved free shear flows should provide a better understanding of these complex flow problems. In this work, we study the development of Görtler vortices inside a curved shear layer in both the incompressible and compressible regimes using a numerical solution to a parabolized form of the Navier-Stokes equations, in the assumption that the stream- wise wavenumber associated with the vortex flow is much smaller than the crossstream wavenumbers. Various results consisting of contour plots of centrifugal instabilites in cross- flow planes, and energy and streak amplitude distributions along the streamwise direction are reported and discussed. In addition, we conduct a biglobal stability analysis to study the growth rates and the eigenmodes associated with these flows.

AB - Curved free shear layers exist in many engineering problems involving complex flow geometries, such as the backward facing step flow, flows with wall injection, the flow inside side-dump combustors, or flows generated by vertical axis wind turbines, among others. Most of the studies involving centrifugal instabilities have been focused on wall flows where Taylor instabilities between two rotating concentric cylinders or Görtler vortices in bound- ary layers resulting from the imbalance between centrifugal effects and radial pressure gradients, are generated. Curved free shear layers, however, did not receive sufficient at- tention. An examination of the stability characteristics and the flow structures associated with curved free shear flows should provide a better understanding of these complex flow problems. In this work, we study the development of Görtler vortices inside a curved shear layer in both the incompressible and compressible regimes using a numerical solution to a parabolized form of the Navier-Stokes equations, in the assumption that the stream- wise wavenumber associated with the vortex flow is much smaller than the crossstream wavenumbers. Various results consisting of contour plots of centrifugal instabilites in cross- flow planes, and energy and streak amplitude distributions along the streamwise direction are reported and discussed. In addition, we conduct a biglobal stability analysis to study the growth rates and the eigenmodes associated with these flows.

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Es-Sahli O, Sescu A, Afsar M. Nonlinear centrifugal instabilities in curved free shear layers. 2020. Paper presented at American Institute of Aeronautics and Astronautics (AIAA) SciTech Forum
, Orlando, United States.