USE OF LINEARIZED CFD FOR UNSTEADY AERODYNAMICS FOR GUST LOADS

摘要

Aircraft design loads are a key driver influencing the aircraft empty weight and hence influencing aircraft performance and operating cost. Apart from determining safe and reliable design loads, another objective is then to determine also rational and realistic loads levels. An alternative to generate unsteady aerodynamics matrices based on linearized Unsteady Reynolds Averaged Navier Stokes (URANS) calculations in the frequency domain taking also into account flexible deformations has been investigated. In contrast to the presently applied doublet lattice method (DLM) the Computational Fluid Dynamics (CFD) method provides a better representation of the physics in the transonic regime and especially for more complex geometries like for instance engine-pylon-wing configurations. In a first step CFD data has been applied without any corrections in gust loads computations. In the standard Airbus process a correction is applied on the aerodynamic influence coefficients coming from the doublet lattice method in order to match steady aerodynamic. An approach has been found to correct the CFD data accordingly. Generalized aerodynamic forces from corrected and uncorrected aero data have been compared showing that the uncorrected CFD data are already much closer to the wind tunnel data for the quasi steady part than those from uncorrected DLM. Furthermore, loads have been computed from CFD and DLM data and compared.