Comparisons of aeroelastic computer code predictions against measured rotor vibratory response data

Abstract

A preliminary inviscid version of the NASA LeRC/Mississippi State University 3-D aeroelastic computational fluid dynamics code, TURBO-AE, is evaluated using operating conditions from three test cases from an AlliedSignal Engines (AE) advanced technology integrally bladed fan rotor. Two of the cases corresponded to conditions where high op-line flutter vibrations were observed, and the third case was flutter-free during testing. TURBO-AE steady (no blade vibration) computations were performed for each test case and a reasonable match was found with the steady 3-D viscous code DAWES. Following completion of the steady computations, TURBO-AE flutter (blade vibration) analyses were completed by harmonically oscillating the airfoil with mode shapes computed by the structural finite-element code ANSYS. Aerodynamic work per vibration cycle and modal damping was computed by TURBO-AE at 0° and 180° Inter Blade Phase Angles (IBPA). For IBPA = 0°, TURBO-AE predicted aerodynamic damping to be low but positive. Further, for IBPA = 180°, the TURBO-AE predictions indicate a very high level of aerodynamic damping. Flutter was observed on the rotor only for IBPA = 32.7°, and TURBO-AE analyses are in process for this condition. Unsteady pressure perturbation contour plots are presented to aid in the visualization of the TURBOAE flow solution. Results presented in this paper indicate that, although TURBO-AE still requires significant development, it is making the difficult transition from a research code to a flutter and forced-response prediction tool for the U.S. aeropropulsion community.