Global Instability and Control of Low-Pressure Turbine Flows

Abstract

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send cornments regarding this burden estimate or any other aspect of this collection of information, including suggestions for redudng this burden to Department of Defense, Washington Headquarters Services, Directorate for Information SUPPLEMENTARY NOTES ABSTRACTThis final report covers the 35-month period from Ferbuary 1, 2003, the inception of the grant, to its end on December 31, 2005. Within the present effort BiGlobal primary and secondary (Floquet) instability analyses of Low Pressure Turbine (LPT) flows were performed for the first time. The T-106/300 LPT blade was selected and used for the analyses reported herein. In addition, two-and three-dimensional direct numerical simulations (DNS) were employed respectively in order to provide the nonparallel steady and unsteady two-dimensional basic flows to be analyzed and in order to cross-validate primary and secondary BiGlobal instability analysis results. Calculations were performed at chord Reynolds numbers of 900 and 5000 using both structured and unstructured grids. Finally, the first-ever transientgrowth analysis of a nonparallel flow field was performed in the context of the LPT flow investigated herein. In the entire range investigated, unstable three-dimensional modes were discovered; as the three-dimensional flow approaches the two-dimensional limit, the time-periodic basic state is recovered. FINAL REPORT Grant F49620-03-1-0295 (Theofilis) -"Global instability and control of low-pressure turbine flows"

DNS of secondary flows over oscillating low-pressure turbine using spectral/hp element method

“…Michelassi et al [41] conducted LES simulations to analyze the combined effect of reduced frequency and flow coefficient associated with the incoming wakes on the aerodynamic performance, particularly profile losses, of the T106A low-pressure-turbine profile. Moreover, two-and three-dimensional BiGlobal instability analyses of the incompressible basic flows in a low-pressure turbine passage are reported in a study presented by Theofilis et al [42]. In their study, the mechanism associated with linear instabilities of the flow are investigated using a spectral/hp element method in order to understand the characteristics of flow instabilities over a stationary low-pressure turbine blade.…”

Fundamentals and Applications of Modern Flow Control

“…The synergisms between experiments (Bons et al, 2001aHuang et al 2006a, b;Sondergaard et al, 2002a, b), numerical simulations Fasel, 2005a, b, 2007a;Postl, 2005;Postl et al, 2003Postl et al, , 2004Rizzetta and Visbal, 2004, and linear stability analysis (Abdessemed et al, 2004(Abdessemed et al, , 2006Theofi lis and Sherwin, 2004) resulted in a signifi cant step forward in the understanding of the physical mechanisms that are relevant for LPT separation control. The experiments at AFRL by Rivir and co-workers have convincingly demonstrated the potential benefi ts of AFC using VGJs.…”

On Global Linear Instability Mechanisms of Flow Around Airfoils at Low Reynolds Number and High Angle of Attack

“…The first such efforts regarding global instability of flow around the NACA0012 airfoil were reported by Theofilis & Sherwin 1 , followed by the work of Theofilis et al 2 . Encouraged by the capability of the analysis to identify, for the first time, linear instability in the wake of the airfoil as a global eigenmode, without resorting to the approximations of weakly-nonparallel flow used prior to those analyses, work by Abdessemed et al 3 was performed in order to identify linear global instability mechanisms in a Low Pressure Turbine (LPT) passage.…”