Large-amplitude excitations need to be considered for gust load analyses of transport aircraft in cruise flight conditions. Nonlinear amplitude effects in transonic flow are, however, only marginally ...taken into account. The present work aims at closing this gap by means of systematic unsteady Reynolds-averaged Navier-Stokes simulations. The RAE2822 airfoil is analyzed for a variety of sinusoidal gust excitations at different transonic Mach numbers. Responses are evaluated with respect to lift and moment coefficients, their derivatives and the unsteady shock motion. A strong dependency on inflow Mach number and excitation frequency is observed. Generally, amplitude effects decrease with lower Mach numbers or higher excitation frequencies. The unsteady nonlinear simulations predict lower maximum lift values and lower lift and moment derivatives compared to their linear counterparts for lower frequencies in combination with large-amplitude excitations. For the mid-frequency range, trends are not as clear. Additionally, it is shown that the variables of harmonic distortion and maximum shock motion might not be reasonable indicators to predict a nonlinear response.
This paper presents the results from three-dimensional fluid–structure interaction simulations of an aeroelastic wind tunnel experiment which was conducted in the Transonic Wind Tunnel in Göttingen, ...Germany in 2013. The experimental setup consisted of two wings: a rectangular NACA0010 wing, which was used as a gust generator, and further downstream a three-dimensional elastic wing representing the outer part of a typical transport-aircraft wing, the so-called ‘Aerostabil’ wing. Laminar-turbulent boundary layer transition has been tripped to generate turbulent flow. The investigations in this paper are focused on the numerical influence of fixed transition compared to fully turbulent simulations. The effect of the different aerodynamic modeling becomes most obvious for higher angles of attack. Steady aeroelastic simulations including fixed transition modeling show more accurate numerical results than the fully turbulent simulations when compared to experimental data. Moreover, unsteady simulations reveal a significant reduction of unsteady loads for simulations with fixed transition compared to fully turbulent simulations.
A quasi-steady doublet-lattice correction method is used to predict aerodynamic gust responses of two different configurations: a swept wing, the so-called Aerostabil wing, and a transport aircraft ...configuration, the NASA Common Research Model. The results of the correction method are compared to uncorrected doublet-lattice results, and to results obtained from a nonlinear computational fluid dynamics solver, the DLR TAU-Code. The correction method agrees well with time-marching results obtained by TAU in the limit of dynamically linear gust amplitudes and improves with gust length. In separated transonic flow, an oscillation of the aerodynamic gust response can be computed.
PDF
