variavel0=<b>ROBERTO GIL ANNES SILVA</b> - rasilva@iae.cta.br IAE
<b>OLYMPIO ACHILLES DE FARIA MELLO</b> - oamello@directnet.com.br IAE
<b>JOĆO LUIZ FILGUEIRAS DE AZEVEDO</b> - azevedo@iae.cta.br IAE
<b>Abstract.</b> Approximate flutter analyses in transonic flow typically employ a linear flutter package with the inclusion of the nonlinear transonic effects, by applying corrections to the aerodynamic influence coefficient matrices. However, such analyses implicitly require that transonic aerodynamic loads are "locally" linear with respect to structural deformation about a given geometry. This linear behavior has been previously shown for the case of the solution of the transonic small disturbance equation (TDSE) in twodimensional flow for small angle of attack variations, which allows a "linear boundary" to be established and appears to justify using approximate flutter analyses. In order to take in account the viscous effects, the present work employs a numerical Navier- Stokes code to verify the "locally" linear behavior of aerodynamic loads with respect to the variation of the static angle of attack. This study is aimed at identifying the conditions under which approximate flutter analyses based on corrections to aerodynamic influence coefficients may be used. The results show that viscous effects play a fundamental role in shock displacement over the airfoil, which prompts the re-evaluation of the previous inviscid-based linear boundaries. Thus, the locally linear behavior in transonic flow should be approached with care when applied to transonic flutter analysis.
<b>Keywords.</b> Transonic Flow, Navier-Stokes, Computational Fluid Dynamics, Linear-Non Linear Behavior.