Numerical Simulation of Transonic Flutter Suppression by Active Control

Abstract

Transonic flutter and active flap control, in two dimensions, is simulated by coupling independent structural dynamic and inviscid aerodynamic models, in the time domain. The accuracy and CPU requirements of the two common approaches, namely ‘weak’ and ‘strong’ coupling procedures, are investigated. It is found that the strong coupling scheme is more accurate than the weak coupling approach, and only for large real time-steps is the strong coupling scheme more expensive. The computational method developed is used to perform transonic aeroelastic and aeroservoelastic calculations in the time domain, and used to compute stability (flutter) boundaries of 2-D wing sections. A control law is implemented within the aeroelastic solver to investigate active means of flutter suppression via control surface motion. Open and closed loop simulations show that active control can successfully suppress the flutter and results in a significant increase in the allowable speed index in the transonic regime. Flowfield analysis is used to investigate the nature of flutter and active control, in terms of shock wave motion in the vicinity of the flap.