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A mechanism for control of turbulent separated flow in rectangular diffusers

Published online by Cambridge University Press:  18 October 2011

Hayder Schneider ,
Dominic A. Von Terzi ,
Hans-Jörg Bauer  and
Wolfgang Rodi
Hayder Schneider*
Affiliation:
Institute for Thermal Turbomachinery, Karlsruhe Institute of Technology, Kaiserstraße 12, 76128 Karlsruhe, Germany
Dominic A. Von Terzi
Affiliation:
Institute for Thermal Turbomachinery, Karlsruhe Institute of Technology, Kaiserstraße 12, 76128 Karlsruhe, Germany Aeronautics Department, Imperial College London, Prince Consort Road, London SW7 2AZ, UK
Hans-Jörg Bauer
Affiliation:
Institute for Thermal Turbomachinery, Karlsruhe Institute of Technology, Kaiserstraße 12, 76128 Karlsruhe, Germany
Wolfgang Rodi
Affiliation:
Institute for Hydromechanics, Karlsruhe Institute of Technology, Kaiserstraße 12, 76128 Karlsruhe, Germany
*
†Email address for correspondence: hayder.schneider@kit.edu
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Abstract

The turbulent separated flow through an asymmetric diffuser with and without manipulation of incoming turbulence-driven mean secondary vortices (MSVs) from a rectangular duct is investigated by large-eddy simulations. The simulations carried out for two diffuser geometries reveal that by introducing a small amount of mean-flow kinetic energy via the MSVs into the flow, the complex three-dimensional separation behaviour and pressure recovery can be effectively controlled. Manipulated MSVs were found to enhance cross-sectional transport of high-momentum fluid, which determined the location, shape, and size of the separation bubble. The integral effect was a delay or expedition in the onset of separation. This change strongly affected the conversion of mean-flow kinetic energy to pressure, in particular for the front part of the diffuser. In addition, a substantial reduction in total pressure loss could be achieved. The manipulation of the MSVs is an efficient mechanism for performance enhancement in the cases investigated. The results have important implications for both control and statistical modelling of turbulent separated flow in rectangular diffusers.

JFM classification

Flow Control: Flow Control Turbulent Flows: Turbulent Flows
Type
Papers
Information
Journal of Fluid Mechanics , Volume 687 , 25 November 2011 , pp. 584 - 594
Copyright
Copyright © Cambridge University Press 2011

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Footnotes

‡

Current address: GE Global Research, 85748 Garching/Munich, Germany

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