A parametric analysis of reduced order models of viscous flows in turbomachinery

The unsteady flow created by a cascade of oscillating airfoils is investigated. A frequency-domain model is constructed and the proper orthogonal decomposition technique is applied to construct several reduced order models of subsonic and transonic flows. A cascade of NACA-5506 airfoils is numerically investigated to show that reduced order models with only 35 degrees of freedom accurately predict the unsteady response of the full model with approximately 6000 degrees of freedom in the subsonic regime, for a broad range of Mach numbers. In the transonic regime, 55 degrees of freedom were shown to be required to accurately predict the response of the full model. The increased number of degrees of freedom is shown to be due to the presence of the shock and not the increase in the Mach number per se. (C) 2003 Elsevier Science Ltd. All rights reserved.