A COMPREHENSIVE FRAMEWORK FOR THE COUPLED NONLINEAR AEROELASTIC AND FLIGHT DYNAMIC ANALYSES OF HIGHLY FLEXIBLE AIRCRAFT

A comprehensive framework to model and analyze the coupled nonlinear aeroelasticity and flight dynamics of highly flexible aircraft is presented. The methodology is based on the dynamics of 3-D co-rotational beams. The coupling of axial, bending and torsional effects is added to the stiffness and mass matrices of Euler-Bernoulli beam to capture the most relevant characteristics of real wing structure. Finite-state aerodynamic model is coupled with the structural model to simulate the unsteady aerodynamics. And the full-wavelength 1-cos time-varying discrete gust model with spatial distribution is proposed and adopted. A scheme of mixed end-point and mid-point time-marching algorithms is proposed and applied into the implicit predictor-corrector integration, so as to improve the calculation efficiency and accuracy. The ground, body and airflow axes for flight dynamics are re-defined by elemental ones of structural dynamics, followed by the redefinitions of local Euler angles and airflow angles of each element. The framework can be used for quick analyses of flexible aircraft in conceptual and preliminary design phases, including linear and nonlinear trim, aerodynamic load estimation, stability assessment, time-domain simulations and flight performance evaluations. With the framework and calculation program proposed in this paper, the process and internal mechanism of the disintegration mishap of Helios Prototype is revealed.