Parametric Flutter Margin Analysis with CFD-Based Aerodynamics

摘要

The recently developed Parametric Flutter Margin (PFM) methodology is applied for efficient flutter analysis with CFD-based unsteady aerodynamics. The PFM method is based on adding a stabilizing element, such as generalized damping of the first bending mode, and extracting the flutter characteristics of the original aeroelastic system from response simulations performed with the modified one. Being stable over the simulation range of air velocities, exact flutter onset characteristics are obtained with a small number of simulations. Two approaches for performing the fluid-structure interaction simulations are proposed. The first one starts with the extraction of linearized aerodynamic force coefficient matrices from CFD response to modal excitation. The resulting matrices are subsequently used in a linear PFM analysis. The second one consists of performing tight-coupling simulations where at each time step generalized aerodynamic forces and model displacements are exchanged between the CFD and the aeroelastic response solver. The Increased-Order Modeling methodology is utilized for preforming these simulations due to its ability to efficiently include time-domain nonlinear effects in frequency-domain aeroelastic formulation. The two PFM approaches are used for proof-of-concept CFD-based flutter analysis of a NACA0012 aeroelastic model in an inviscid and incompressible regime and the results are compared for validation with classical ones.