Nonlinear Low-Dimensional Model Order Reduction with Subspace Interpolation for Gust Applications with the Linear Frequency Domain Approach

Abstract

Gust load predictions are time-consuming for aircraft design since these are unsteady events and depend not only on the flow conditions but also on many other parameters such as weight and altitude changes. The linear frequency domain solver allows a rapid calculation of gust loads in contrast to a time-accurate method, although the calculation of several harmonics is necessary to reconstruct the equivalent time signal. A further increase in efficiency can be obtained with the use of a Proper Orthogonal Decomposition-Galerkin method for interpolating certain frequencies for the gust time signal for a single operating point of the flight envelope. If several operating points are already known, an interpolation of gust loads between the operating points can be performed on the Grassmann manifold. Considering the flight conditions, subsonic to transonic, of a whole flight envelope, the Proper Orthogonal Decomposition-Galerkin method achieves a good prediction accuracy. For the Grassmann manifold, however, it turns out that it is only suitable in the immediate vicinity of sampled operating points.