Verification of calculation methods for unsteady airloads in the prediction of transonic flutter

Abstract

Various engineering-type methods to calculate unsteady airloads on wings in transonic flow were applied in flutter calculations for a semispan flutter model of a supercritical wing. Verification was performed on the basis of comparing flutter characteristics, in which special attention was given to the prediction of transonic dips in the flutter boundaries. The methods were able to produce useful results when applied complementarity. ^0.95 Nomenclature b = dimensionless shift of aerodynamic center c =wing section chord, m C/n = sectional mean lift coefficient pressure coefficient at 0.95 chord, 0.7 span, upper side / = frequency, Hz k = reduced frequency related to semichord ka,ma = sectional unsteady lift and moment coefficients (AGARD notation, m related to 0.25 chord); kij.my = sectional unsteady lift and moment influence coefficients (induced by strip j, at strip /) MOO = Mach number P0 —