Study of Reduced-Order Models for Gust-Respnse Analysis of Flexible Fixed Wings

Three types of aeroelastic reduced-order models (ROMs) for flutter and gust-response analyses are examined, one of which is introduced here. One is based on the finite-state description of unsteady aerodynamics obtained through a rational-matrix approximation of the frequency-domain transcendental aerodynamic operator. Coupling this with the equations of the structural dynamics yields the aeroelastic ROM. The drawback of this approach is some aerodynamic states have to be added to the structural states in the state-space format description of the aeroelastic system. The second model that is discussed yields directly the finite-state description of the aeroelastic operator without altering the dimensions of the state space. This model is iterative in nature, in that it requires an estimate of aeroelastic eigenvalues and eigenvectors from the original eigenproblem. Finally, an alternate ROM for the gust-response problem is proposed. It combines good level of accuracy with reduction of additional aerodynamic states and thus can be conveniently used in preliminary design process and control-law synthesis.