CFD-based Gust Load Analysis for a Free-flying Flexible Passenger Aircraft in Comparison to a DLM-based Approach

Abstract

Gust load analysis is a relevant part of the certification process of aircraft. In need of low computing times, industrial analysis procedures often rely mainly on low-fidelty numerical aerodynamics methods, such as the Doublet Lattice method (DLM). However, their accuracy with respect to loads has not been assessed sufficiently in comparison to high-fidelity methods in the past. In this paper, simulation results of a classical DLM-based gust load analysis process are compared to the results of an alternative process in which the DLM solver is replaced by the CFD solver TAU. The investigation is performed with a realistic modern passenger aircraft. It is studied how the consideration of different levels of multidisciplinarity in the simulations affects the overall loads. The simulation methodologies exploited in the CFD-based analysis process are outlined. It is shown that the gust load factors predicted with CFD are significantly lower than those of the classical DLM-based process, not only in the transonic flow regime, where benefits from the CFD-based analysis are expected, but also in the subsonic flow regime.