Time-Domain Simulation for Evaluating SmartWing Concepts

Abstract

A numerical simulation for predicting and evaluating methods to control the response of an elastic wing in a steady or an unsteady airstream is discussed. The simulation consists of five parts: a model of the structure, a model of the flowfield, a model of the control system, a method for combining the models, and a numerical scheme to integrate all of the governing equations interactively and simultaneously in the time domain. The approach considers the air, the deforming wing, and the controller as elements of a single dynamical system. The method is modular, allowing independent modifications to the aerodynamic, structural, and control subsystems and it is not restricted to periodic motions or simple geometries. As a demonstration of the technique and its capabilities, we investigate the active control a High Altitude, Long Endurance (HALE) aircraft wing in typical flight conditions, including gusts. The wing is modeled structurally as a linear Euler-Bernoulli beam that includes dynamic coupling between the bending and torsional oscillations. It is discretized via finite-elements. Our version of the general nonlinear unsteady vortex-lattice method, which is capable of simulating arbitrary subsonic maneuvers of the wing and accounts for the history of the motion, is employed to model the aerodynamics. Feedback control via a distributed actuator is used for flutter and gust-load alleviation. In the simulations, flutter is readuly suppressed, but presently, peak gust loads are only marginally reduced.