Comparison of Reduced Order Models for Evaluating Stability Derivatives for the DLR-F22 ONERA model

Abstract

This paper presents a comparison of reduced order models to predict aerodynamic stability derivatives. The study involved two widely used frameworks for simulating unsteady flows, DoD HPCMP CREATERM-AV/Kestrel and the DLR TAU code. The DLR TAU code contains a linearized version of the discrete unsteady Reynolds-averaged Navier-Stokes equations based on the small perturbation approach which are solved in the frequency domain. This allows a comparison with distinctly different approaches of reduced order aerodynamic modeling. The first approach is based on the linear frequency domain solver which computes stability derivatives directly. Three reduced order models are applied to unsteady simulations to extract stability derivatives from predicted time histories of the force and moment coefficients. The first reduced order model is the stability derivatives method. The second reduced order model is based on the calculated indicial responses to unit step changes in the angle of attack and pitch rate. Furthermore, a system identification approach is applied to the time history of the force and moment coefficients for different training maneuvers to extract the stability derivatives. The weaknesses and strengths of the individual approaches of reduced order models are shown and, in particular, the efficiency of the methods is outlined. The use case is the DLR-F22 ONERA model, a generic research wind tunnel model of a triple delta wing fighter type aircraft configuration, at transonic flow conditions for various angles of attack.