Continuation method for calculation of transonic airfoil flutter boundaries

Flutter boundaries, through variations in aerodynamic and structural dynamic parameters, are computed for a NACA 64A006 airfoil at transonic freestream Mach numbers with pitch-and-plunge structural coupling, These Butter boundaries are obtained with a new continuation algorithm that specifically accounts for flutter onset, The algorithm, which is based on pseudoarclength continuation, solves an extended form of the Euler equations for the reduced velocity at flutter onset, the corresponding base-flow solution, the destabilizing mode at Butter onset, and the critical value of a secondary structural parameter, e.g., structural damping, The algorithm provides a relatively automated procedure for computing flutter boundaries directly, which avoids a trial-and-error, Butter-detection process typical of time-domain techniques. The current method is validated through comparison with independent flutter-boundary computations. Grid-sensitivity studies are carried out to assess the numerical accuracy of computed solutions.