Modeling delta wing limit-cycle oscillations using a high-fidelity structural model

Flutter and limit-cycle oscillations(LCO) of a delta-wing model are studied theoretically and correlated with results from an earlier experiment and an earlier simpler theoretical model. The present theoretical model uses a high-fidelity nonlinear structural model and a linear vortex lattice aerodynamic model. The commercial finite element package ANSYS is selected to model the structure and is coupled to the vortex lattice aerodynamic model using a subiteration procedure to carry out time simulations. The delta-wing model is studied for five angles of attack (0, 1, 2, 3, and 4 deg) and for various flow speeds. Theoretical results are calculated for two different root-chord boundary conditions, that is, fully fixed and also another that allows some in-plane movement at the root chord by attaching stiff in-plane springs that connect the structure to the root boundary. The results obtained using the high-fidelity structural model are compared to earlier results computed using a lower-fidelity von Karman plate theory. For all angles of attack studied here, the correlation between theory and experiment is better for the aeroelastic model, which uses the high-fidelity (ANSYS) structural model. Both flutter velocity and frequency as well as the LCO amplitudes and frequencies that are predicted using the higher-fidelity stuctural model correlate well with experiment. In particular the flutter and LCO results predicted using the high-fidelity structural model are similar, both qualitatively and quantitatively, for the two different in-plane boundary conditions. However the results obtained from the von Karman model differ substantially for the two different in-plane boundary conditions.