STATE-SPACE REALIZATIONS AND MODEL REDUCTION OF POTENTIAL-FLOW UNSTEADY AERODYNAMICS WITH ARBITRARY KINEMATICS

摘要

We introduce a nondimensional state-space formulation of the unsteady vortexlattice method for time-domain aerodynamics. It deals with 2- or 3-dimensional geometries, resolves frequencies up to a spatio-temporal Nyquist limit defined by the wake discretization, and has a convenient form for linearization, model reduction and coupling with structural dynamics models. No assumptions are made relating to the kinematics of the fluid-structure interface (inputs) and use of Joukowski's theorem to compute forces naturally resolves all components of the unsteady aerodynamic forcing (outputs). Linearized expressions are written about arbitrary non-zero reference geometries, velocities and loading distributions and as such yield models that are as general as possible given the assumptions in the underlying fluid mechanics. The implementation is verified against classical solutions in the unsteady aerodynamics, and in aeroelastic stability analysis of cantilever wing configurations.