Aeroelastic Gust Load Prediction Based on Time-Linearized RANS Solutions

In this paper the multi-disciplinary simulation of unsteady flight maneuvers with a reduced-order model (ROM) based on time-linearized RANS solutions is demonstrated for the analysis of gust encounter of the XRF1 transport aircraft configuration at transonic speed. The numerical prediction of gust loads requires the coupling of the disciplines aerodynamics, structural dynamics and flight mechanics. The aeroelastic coupling is realised in the frequency domain in terms of generalized coordinates and forces employing a fluid-structure feedback loop. The Linear Frequency Domain (LFD) solver of the DLR TAU code is used to construct the linearized aerodynamic reduced-order model. The LFD solver offers a significant reduction in computational effort for small-perturbation problems while completely retaining the fidelity of the Reynolds-averaged Navier-Stokes (RANS) flow solutions. For validation, both the aerodynamic and aeroelastic response due to a 1-cos gust encounter are compared to aerodynamically nonlinear time domain simulations. The coupled aeroelastic model accounts for rigid-body and elastic motion of the aircraft in form of mode shapes for the heave and pitch motion as well as the first elastic wing bending mode.