Three-Dimensional Aeroelastic Solutions via the Nonlinear Frequency-Domain Method

An aeroelastic solver is developed using a nonlinear frequency domain flow solver coupled to a plate-bending finite element linear structural solver. A methodology for determining the flow conditions leading to flutter and limit-cycle oscillations is proposed, based on a root-finding Newton-Raphson iterative method. The novelty of the approach lies in the constant size of the Newton-Raphson system of equations, regardless of the number of degrees of freedom of the structural model. To serve this purpose, a new method of computing mesh velocities for nonlinear frequency-domain flow solvers is developed, and a technique for solving the geometric conservation law within the nonlinear frequency-domain framework is presented accordingly. The new approach for computing mesh velocities is validated against existing experimental data on the Lockheed, Air Force, NASA and Netherlands wing (run 73, CT5), whereas the aeroelastic solver is validated via experimental results of the AGARD I.-wing weakened model 3 and solid model 2 in air and R-12, respectively. The proposed framework is expected to perform limit-cycle oscillation computations an order of magnitude faster than a typical aeroelastic time-marching approach.