Efficient Surrogate Modelling of Nonlinear Aerodynamics in Aerostructural Coupling Schemes

This paper considers the substitution of the computational-fluid-dynamics solver within an aerostructural coupling scheme by an efficient reduced-order surrogate model to realize high-fidelity nonlinear aeroelastic analyses within a fraction of the time compared to the corresponding coupled computational-fluid-dynamics analysis. The presented surrogate model approach is a combination of parameter reduction via proper orthogonal decomposition and system identification methods designed to cover nonlinear aerodynamic effects such as viscosity as well as transient effects. The investigated test case is the thick NLR7301 airfoil that shows significant nonlinear aerodynamic behavior along with nonnegligible viscous effects. The model is identified from a set of transient forced motion computational-fluid-dynamics analyses. After identification, the model is used to predict the discrete surface force distribution of the NLR7301 airfoil in static as well as transient coupled analyses. It is shown that the static aeroelastic equilibrium and the limit cycle oscillation case is predicted by the surrogate model with sufficient accuracy.