Analytical and Experimental Study of Subsonic Stalled Flutter.
Final rept. 1 Apr 75-31 May 77,
PRATT AND WHITNEY AIRCRAFT GROUP WEST PALM BEACH FLA GOVERNMENT PRODUCTS DIV
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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 OSRSQUID 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.
- Fluid Mechanics
- Jet and Gas Turbine Engines