Linear instability analysis of low-pressure turbine flows

Abdessemed, Nadir and Sherwin, Spencer and Theofilis, Vassilios (2009). Linear instability analysis of low-pressure turbine flows. "Journal of Fluid Mechanics", v. 628 ; pp. 57-83. ISSN 0022-1120.


Title: Linear instability analysis of low-pressure turbine flows
  • Abdessemed, Nadir
  • Sherwin, Spencer
  • Theofilis, Vassilios
Item Type: Article
Título de Revista/Publicación: Journal of Fluid Mechanics
Date: June 2009
Volume: 628
Faculty: E.T.S.I. Aeronáuticos (UPM)
Department: Motopropulsión y Termofluidodinámica [hasta 2014]
Creative Commons Licenses: Recognition - No derivative works - Non commercial

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Three-dimensional linear BiGlobal instability of two-dimensional states over a periodic array of T-106/300 low-pressure turbine (LPT) blades is investigated for Reynolds numbers below 5000. The analyses are based on a high-order spectral/hp element discretization using a hybrid mesh. Steady basic states are investigated by solution of the partial-derivative eigenvalue problem, while Floquet theory is used to analyse time-periodic flow set-up past the first bifurcation. The leading mode is associated with the wake and long-wavelength perturbations, while a second short-wavelength mode can be associated with the separation bubble at the tralling edge. The leading eigenvalues and Floquet multipliers of the LPT flow have been obtained in a range of spanwise wavenumbers. For the most general configuration all secondary modes were observed to be stable in the Reynolds number regime considered. When a single LPT blade with top to bottom periodicity is considered as a base flow, the imposed periodicity forces the wakes of adjacent blades to be synchronized. This enforced synchronization can produce a linear instability due to long-wavelength disturbances. However, relaxing the periodic restrictions is shown to remove this instability. A pseudo-spectrum analysis shows that the eigenvalues can become unstable due to the non-orthogonal properties of the eigenmodes. Three-dimensional direct numerical simulations confirm all perturbations identified herein, All optimum growth analysis based on singular-value decomposition identifies perturbations with energy growths O(10(5)).

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Item ID: 5316
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Deposited by: Memoria Investigacion
Deposited on: 01 Dec 2010 12:51
Last Modified: 20 Apr 2016 14:09
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