Analysis of Linearized Motion- and Gust-Induced Airloads with a Next-Generation Computational Fluid Dynamics Solver

ifasd2024 Tracking Number 123

Time-linearized airloads provide a cost-effective way to incorporate unsteady CFD-based methods into aircraft design for assessing loads and stability. RANS methods are necessary to account for non-linearities in modelling transonic or separated flow as required for industrial applications. By limiting excitations around a steady state to very small amplitudes, linearized airloads can be obtained from aerodynamic responses. In this work, two approaches for determining time-linearized motion- and gust-induced airloads [1] are employed within the next-generation CFD framework CODA: the linear frequency domain (LFD) method and the method of system identification in the time domain using forced-motion simulations. The CFD framework CODA comes with improved capabilities regarding the implementation and modelling of the discretized flow. In particular, automatic differentiation of the implemented equations directly enables the evaluation of the flux Jacobian as needed for the LFD solver [2]. Employing both considered approaches in a unified setting allows verifying the consistent implementation of CODA’s LFD solver and the unsteady time-integration scheme with moving meshes. Figure 1 shows the agreement of the two approaches for the NACA64 A010 airfoil in transonic flow undergoing pitching oscillations of varying frequencies as well as for a sinusoidal gust excitation. This work investigates several configurations including the NASA Common Research Model in terms of unsteady integral forces and pressure distributions resulting from rigid body and elastic motion as well as from gusts in varying flow regimes and for different turbulence models. Moreover, the conducted analysis provides the groundwork for verifying aeroelastic studies based on linearized airloads like flutter onset predictions with aeroelastic timemarching simulations employing CODA.