State-space representation of unsteady airfoil behavior

Abstract

A method is presented to model the unsteady lift, pitching moment, and drag acting on a two-dimensional airfoil operating under attached-flow conditions in a compressible flow. Starting from suitable generalizations and approximations to aerodynamic indicial functions, the unsteady airloads due to an artibrary forcing are represented in a state-space (differential equation) form. This model is in a form compatible with the aeroelastic analyses of both fixed-wing and rotary-wing systems