Stability and Open-Loop Dynamics of Very Flexible Aircraft Including Free-Wake Effects

Abstract

The paper investigates the coupled aeroelasticity and flight mechanics of very flexible lightweight aircraft. A geometrically-exact composite beam formulation is used to model the non-linear flexible-body dynamics, including rigid-body motions. The aerodynamics are modeled by a general 3-D unsteady vortex-lattice method, which can capture the instantaneous shape of the lifting surfaces and the free wake, including large displacements and interference effects. The coupled governing equations are solved in a variety of ways, including linear and non-linear time-domain simulations of the full vehicle and frequencydomain linear stability analysis around trimmed configurations. The resulting framework for the Simulation of High-Aspect Ratio Planes (SHARP) provides a mid-fidelity representation of flexible aircraft dynamics, based on an intuitive and easily linearizable structural representation based on displacements and the Cartesian rotation vector, time-domain 3-D aerodynamics, and at relatively low computational costs. Previous verification studies on the structural dynamics and aerodynamics modules are complemented here with studies on the flexible-body implementation and on the integrated simulation methodology. A numerical investigation is finally presented on a representative high-altitude long-endurance model aircraft, investigating its stability properties and its open-loop dynamic response.

An Intrinsic Description of the Nonlinear Aeroelasticity of Very Flexible Wings

“…2,11,[20][21][22] Its relevant properties are included in Table 1. It should be noted that this definition corresponds to the original description due to Goland,19 instead of the heavy version (often referred to as Goland + ) of Eastep and Olsen.…”

Integrated Flight Dynamics and Aeroelasticity of Flexible Aircraft with Application to Swept Flying Wings

“…13 Finally, the orientation of the body-fixed reference frame with respect to an inertial frame is parameterized using quaternions, denoted by χ, and computed by solving an extra set of attitude EoM. 14,15 Together with the Eq. (1) this completes the geometrically nonlinear description of the aircraft structural dynamics and nonlinear rigidbody motion.…”

Predictive Control for Alleviation of Gust Loads on Very Flexible Aircraft

“…14 At last, the orientation of the body-fixed reference frame with respect to an inertial frame is parameterized using quaternions, denoted by χ, by solving an extra set of attitude EoM. 15,16 Together with the Eq. (1) this completes the geometrically nonlinear description of the aircraft structural dynamics and nonlinear rigid-body motion.…”