Experimental and theoretical studies in nonlinear aeroelasticity

Experimental and theoretical studies are conducted in the field of nonlinear aeroelasticity. Specifically two aeroelastic configurations, a flapping flag and a delta wing, are investigated and correlations between theory and experiment are presented.; Two nonlinear structural theories are used to describe the structural behavior of the two models which are studied. The delta wing structural behavior is modeled using the nonlinear plate theory of von Karman. The nonlinearity in this model is due to the coupling between the out-of-plane and in-plane deflections and the model allows for moderately large out-of-plane plate deflections. The flapping flag structural model is a nonlinear beam theory which includes nonlinearities due to both large curvature and inertia. The axial deflection in this model is related to the out-of-plane deflection using an axially inextensible theory.; The aerodynamic theory used is potential flow theory, which is applicable to low speed flows. The equation which describes potential flow is the Laplace equation, which is a linear partial differential equation. The Laplace equation is solved using a vortex lattice method. Aeroelastic solutions are found using both the classic small disturbance linearized fluid-structure interface boundary condition and the exact nonlinear boundary condition. The aeroelastic model which includes the nonlinear boundary conditions also includes a free wake solution.; Several reduced order methods are explored. Normal mode solutions, both for the structural and aerodynamic models, are studied along with a proper orthogonal decomposition model for the aerodynamic flow. A brief description of a parallel implementation of the aeroelastic simulation code is also given and the parallel speedup is shown to be nearly linear for a certain class of problems.; Correlation between theory and experiment is presented for both the delta wing and flapping flag model. Several steady angle of attack cases were investigated for the delta wing configuration at various flow velocities. Flutter and limit cycle oscillation results are presented for both aeroelastic configurations. The theoretical flutter results correlate well with experiment for both the delta wing and flapping flag models. For the delta wing, the correlation between theoretical and experimental LCO magnitude results is fairly good for moderately large angles of attack (<4), with the theoretical model which uses a nonlinear structural theory consistently underpredicting the LCO magnitude. For this aeroelastic configuration the dominant nonlinearity appears to be structural.; The flapping flag theoretical model also underpredicts the LCO magnitude. It also fails to model the LCO hysteresis which is measured experimentally (with an increase and then a decrease in flow velocity). For this configuration it is not clear as to whether a structural or aerodynamic nonlinearity is dominant. Also wind tunnel blockage effects, which are not modeled, may be important.