Analytical and Experimental Study of Subsonic Stalled Flutter.
Abstract
Experimental and analytical studies were conducted to determine a stall flutter prediction system. The initial phase of work was reported in AFOSR-TR-76-0829 (AD-A027 869): a second study phase, with an extended range of parameters, is documented in this report AFOSR-TR-77-0854. A series of experimental measurements of airfoil pressure distributions were made in an eleven-airfoil oscillating cascade wind tunnel. The air foils were oscillated in pitch about mid-chord pivots with an amplitude of + or - 2 deg at a tunnel velocity of 200 feet-per-second, obtaining reduced frequencies in the range of 0.03 to 0.20. The incident air angle was set at 8 deg, the cascade angle was 35 deg from a fully-closed setting; tests were run at interblade phase angles of zero, + or - 5 deg + or -10 deg + or -20 deg + or -30 deg + or -45 deg and + or - 60 deg. Sample time histories of pressure and hot film response are discussed in relation to previous OSR/SQUID data, and converted to unsteady pressure, lift and pitching moment coefficients. These data are compared with calculated values obtained from a computational program originated by P V Perumal for unsteady incompressible cascade flow with steady separation. An algorithm was fitted to the experimental coefficients, and used to predict the aerodynamic damping for a case of torsional stall flutter observed in the stator of an existing fan. In this calculation, the algorithm was modified by a compressibility correction obtained as the ratio of a cascade calculation for the desired Mach number to a similar calculation for the Mach number of the algorithmic coefficients, both for unseparated flow.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 31, 1977
- Accession Number
- ADA043127
Entities
People
- A. O. St. Hilaire
- F. O. Carta
- R-h. Ni
- R. A. Arnoldi
- W. N. Dalton
Organizations
- Pratt & Whitney