A general solver for the prediction of flutter and buffet onset

Abstract

A versatile solver capable of predicting both flutter and buffet onset, while considering structural feedback, is introduced. The methodology involves computing the (generalized) aerodynamic forces using a linear-frequency-domain (LFD) solver based on linearized unsteady Reynolds-averaged Navier-Stokes equations (URANS) with an appropriate turbulence closure model. A state-space model of the aerodynamic forces is generated through interpolation of the frequency-domain samples, which is the basis of the p-L method. Eigenvalues corresponding to fluid modes may be directly determined, eliminating the need for a priori pole selection as required by traditional rational function approximation techniques. Consequently, the pre- buffet frequency is accurately represented by the imaginary part of the fluid mode's eigenvalue. With this representation of the fluid modes, a flutter solver is derived, which is able to predict both classical flutter and buffet onset values. The solver is applied to the supercritical OAT15A airfoil in the pre-buffet region, verifying its capability to predict both flutter and buffet onset values.