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Unsteady Mechanisms of Compressor Corner Separation Over a Range of Incidences Based on Hybrid LES/RANS

[+] Author Affiliations
Zhong-Nan Wang, Xin Yuan

Tsinghua University, Beijing, China

Paper No. GT2013-95300, pp. V06AT35A030; 11 pages
  • ASME Turbo Expo 2013: Turbine Technical Conference and Exposition
  • Volume 6A: Turbomachinery
  • San Antonio, Texas, USA, June 3–7, 2013
  • Conference Sponsors: International Gas Turbine Institute
  • ISBN: 978-0-7918-5522-5
  • Copyright © 2013 by ASME


The separation flow pattern in compressor corners is well known but its nature is not fully understood. In this paper, the numerical simulation based on hybrid LES/RANS was performed to improve our understanding about the unsteady separation structure and its dynamic mechanisms of compressor corner flows, subject to a range of incoming flow incidences. In the simulation, the attached boundary layer near the walls was modeled by RANS, while the large separated flows in the corner were resolved by LES. The simulation was carefully validated by the experimental data before flow physics investigation. The unsteady separation structures and its effects were then investigated step by step, from phenomena observation to mechanisms analysis. First, the overall separation behavior and its associated flow physics was visualized and analyzed. It was found that the unsteady separation structure was distinct from the steady view. Some additional vortex structures, normally smeared out in the steady averaging process, were crucial in the unsteady dynamic process. These small but critical vortices corresponded to large intermittency in the separation size and strength. As the incidences increased, the vortex structure became much more complex due to the enhanced interaction of these vortices. Second, the turbulence behavior was examined in the separated regions. Anisotropy and non-equilibrium of turbulence were found to be dominant in the separation region due to non-homogenous shear of the separated flow. It posed a big challenge for conventional RANS prediction. Finally, the unsteadiness of corner separated flows was fully analyzed over a range of incidences. It was found that the unsteadiness came from two sources: the suction side separation and the wake shedding. The unsteadiness increased with the incidences. The two unsteady sources interacted with each other at high incidences, which led to a big unsteady resonance structure near the blade trailing edge. The resonance was responsible for a large pressure variation, implying the enhanced noise generation near the blade trailing edge.

Copyright © 2013 by ASME



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