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Large-Scale Unsteadiness in a Two-Dimensional Diffuser: Numerical Study Toward Active Separation Control

Suzuki, Takao and Colonius, Tim (2003) Large-Scale Unsteadiness in a Two-Dimensional Diffuser: Numerical Study Toward Active Separation Control. In: 41st Aerospace Sciences Meeting and Exhibit, 6-9 January 2003, Reno, NV.

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We develop a reduced order model for large-scale unsteadiness (vortex shedding) in a two-dimensional diffuser and study the mechanisms of active flow separation control. This model can estimate the vortex shedding frequency for inviscid flows by accounting for the accumulated vorticity flux in the diffuser. The model can also predict the stagnation pressure loss, which consists of two parts: A steady part corresponds to static pressure loss on the detached area, and an unsteady part is associated with vortex shedding. To validate this model, we perform direct numerical simulation (DNS) of compressible, laminar diffuser flows. The comparison between the model and DNS shows good agreement at various Mach numbers and area ratios of the diffuser in terms of vortex shedding time scale and stagnation pressure loss. To investigate the effects of periodic mass injection near the separation point, we also perform DNS over a wide range of the forcing frequency. The DNS results show that periodic mass injection can pinch off vortices with a smaller size; accordingly, their convective velocity is increased, absorption of circulation from the wall is enhanced, and the extent of the separated region is reduced. As a result, the stagnation pressure recovery, particularly the unsteady part, is substantially improved as predicted by the model.

Item Type:Conference or Workshop Item (Paper)
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URLURL TypeDescription Paper Paper
Colonius, Tim0000-0003-0326-3909
Additional Information:© 2003 by Takao Suzuki and Tim Colonius. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. Published Online: 11 Nov 2012. The DNS code was developed in collaboration with Dr. S. Pirozzoli and Mr. J. Fung. The authors also would like to thank Drs. D. MacMartin, J. Paduano, T. P. Hynes, and Profs. A. P. Dowling, R. Murray, A. Leonard, and H. Nagib for fruitful discussions. This research was sponsored by the DARPA (Defense Advanced Research Project Agency) program (the contract number F49620-00-C-0035).
Funding AgencyGrant Number
Defense Advanced Research Projects Agency (DARPA)F49620-00-C-0035
Subject Keywords:Aerospace Systems, Operations and Life Cycle
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AIAA Paper2003-1138
Record Number:CaltechAUTHORS:20190718-165127428
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:97273
Deposited By: Melissa Ray
Deposited On:26 Jul 2019 18:09
Last Modified:16 Nov 2021 17:30

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