Sensitivity study of downwash weighting methods for transonic aeroelastic stability analysis

Abstract

The paper is concerned with downwash correction methods for aeroelastic stability analyses in the transonic regime. A finite-difference Navier-Stokes code is used to calculate the unsteady aerodynamic loading due to dynamic angle-of-attack variations in three-dimensional transonic flow. The computed unsteady pressure coefficients are used as a reference state for flutter analyses using the downwash weighting method. The effects of the amplitudes of motion used in the calculation of nonlinear, unsteady reference pressures are addressed. The test case considered is the well-known AGARD wing 445.6 standard aeroelastic configuration. The configuration is subjected to rigid-body pitching oscillation about the midchord point at the root section. Flutter boundaries are computed using unsteady pressures, in the downwash correction methodology, as reference conditions to compute weighting operators. The results are compared with available experimental data and they indicate that the aerodynamic interference and viscous and thickness effects play an important role on the flutter prediction capability.